QT5201U wiki - User contributions [en]

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:44:35Z

Bensen: /* Procedure */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.
[[File:C-shaped Electromagnet.jpg|center|thumb|300px|C-shaped Electromagnet]]

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]
[[File:Steel cutter.jpeg|center|thumb|300px|Steel cutter]]
[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be small, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|400px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

[[File:Resistance of the magnet.jpg|center|thumb|400px|Resistance measured]]

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>[[File:Spin1.png|center|400px]][[File:Spin2.png|center|400px]]
# Use hall probe connected to sample to readout the result

==Results==
* Just finished the fabrication of electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:39:58Z

Bensen: /* Fabrication of C-shaped electromagnet */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.
[[File:C-shaped Electromagnet.jpg|center|thumb|300px|C-shaped Electromagnet]]

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]
[[File:Steel cutter.jpeg|center|thumb|300px|Steel cutter]]
[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be small, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|400px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

[[File:Resistance of the magnet.jpg|center|thumb|400px|Resistance measured]]

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>

[[File:Spin1.png|center|400px]]
[[File:Spin2.png|center|400px]]

# Use hall probe connected to sample to readout the result

==Results==
* Just finished the fabrication of electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:35:00Z

Bensen: /* Results */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.
[[File:C-shaped Electromagnet.jpg|center|thumb|300px|C-shaped Electromagnet]]

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]
[[File:Steel cutter.jpeg|center|thumb|300px|Steel cutter]]
[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|400px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

[[File:Resistance of the magnet.jpg|center|thumb|400px|Resistance measured]]

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>

[[File:Spin1.png|center|400px]]
[[File:Spin2.png|center|400px]]

# Use hall probe connected to sample to readout the result

==Results==
* Just finished the fabrication of electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:34:09Z

Bensen: /* Procedure */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.
[[File:C-shaped Electromagnet.jpg|center|thumb|300px|C-shaped Electromagnet]]

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]
[[File:Steel cutter.jpeg|center|thumb|300px|Steel cutter]]
[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|400px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

[[File:Resistance of the magnet.jpg|center|thumb|400px|Resistance measured]]

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>

[[File:Spin1.png|center|400px]]
[[File:Spin2.png|center|400px]]

# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:30:00Z

Bensen: /* Experimental setup */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.
[[File:C-shaped Electromagnet.jpg|center|thumb|300px|C-shaped Electromagnet]]

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]
[[File:Steel cutter.jpeg|center|thumb|300px|Steel cutter]]
[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|400px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

[[File:Resistance of the magnet.jpg|center|thumb|400px|Resistance measured]]

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

File:Spin1.png

2021-04-30T14:29:42Z

Bensen:

File:Spin2.png

2021-04-30T14:29:16Z

Bensen:

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:24:17Z

Bensen: /* Principle */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.
[[File:C-shaped Electromagnet.jpg|center|thumb|300px|C-shaped Electromagnet]]

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]

[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|300px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:21:41Z

Bensen: /* Principle */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
[[File:C-shaped Electromagnet.jpg|thumb|300px|C-shaped Electromagnet]]
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]

[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|300px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:21:08Z

Bensen: /* Fabrication of C-shaped electromagnet */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
* The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.

[[File:Raw material for steel core.jpeg|center|thumb|300px|non-grain oriented electrical steel]]

[[File:Laser cutter.jpeg|center|thumb|300px|Laser cutter]]

* Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.

[[File:Copper coil wrapping.jpeg|center|thumb|500px|Copper coil wrapping]]

* Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')

[[File:The magnet.jpg|center|thumb|300px|Final form of the magnet]]

* Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:14:15Z

Bensen: /* Principle */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Hopefully we could observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
[[File:C-shaped Electromagnet.jpg|thumb|200px|C-shaped Electromagnet]]
[[File:Raw material for steel core.jpeg|thumb|200px|non-grain oriented electrical steel]]
[[File:Laser cutter.jpeg|thumb|200px|Laser cutter]]
[[File:Copper coil wrapping.jpeg|thumb|300px|Copper coil wrapping]]
[[File:The magnet.jpg|thumb|300px|Final form of the magnet]]
# The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.
# Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.
# Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')
# Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T14:12:49Z

Bensen: /* Fabrication of C-shaped electromagnet */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Then we will observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
[[File:C-shaped Electromagnet.jpg|thumb|200px|C-shaped Electromagnet]]
[[File:Raw material for steel core.jpeg|thumb|200px|non-grain oriented electrical steel]]
[[File:Laser cutter.jpeg|thumb|200px|Laser cutter]]
[[File:Copper coil wrapping.jpeg|thumb|300px|Copper coil wrapping]]
[[File:The magnet.jpg|thumb|300px|Final form of the magnet]]
# The steel core of the electromagnet we built is made of non-grain oriented electrical steel, by using laser beam, we cut the U-shaped and rectangular pieces out of the steel plate (to form the C-shaped core later). After that, we collected the U-shaped pieces and used screws to cramp all the pieces together, forming a 40mm×40mm U-shaped core.
# Next, we built an acrylic plastic holder to hold the copper wire, we used the manual wrapping machine to wrap the copper coils around the pillar of the plastic holder. The number of coils required for generating 0.5 Tesla is based on the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* According to the calculation, the number of coils of on each side of the magnet should be 250 round.
# Then we built another plastic holder to stack the rectangular piece on the U-shaped steel core, creating the C-shaped core, by drilling holes on the top of the acrylic holder, we can adjust the distance between poles of the magnet. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')
# Lastly, we measured the resistance of the coils, and sent in voltages around 20 Volts to generate 0.05 Tesla out of the magnet (measured by Gauss Metre)

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

File:Laser cutter.jpeg

2021-04-30T13:33:49Z

Bensen: Bensen uploaded a new version of File:Laser cutter.jpeg

File:Raw material for steel core.jpeg

2021-04-30T13:32:03Z

Bensen: Bensen uploaded a new version of File:Raw material for steel core.jpeg

File:IMG 1596.jpeg

2021-04-30T13:26:49Z

Bensen:

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T13:11:41Z

Bensen: /* Fabrication of C-shaped electromagnet */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Then we will observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
[[File:C-shaped Electromagnet.jpg|thumb|200px|C-shaped Electromagnet]]
[[File:Raw material for steel core.jpeg|thumb|200px|non-grain oriented electrical steel]]
# The main components of the electromagnet we are building are non-grain oriented electrical steel, by using laser beam, we cut the C-shaped piece out of the steel plate. After that, we accumulate all the pieces that we cut, forming ... cm thick. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')
# Then we use copper wiles to entwine each pole of the steel, ..., number of coils required for generating ... radio frequency pulse is according to the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* <math>B=2\mu_0nI</math>
#** <math>\mu_0=4\pi\times10^{-7}(\text{T}\cdot\text{m}/A)</math>
#** n is the number of loops per unit length of the solenoid (<math>n=\frac{N}{L}</math>, with N being the number of loops and L the length)
# Next, connect the electromagnet we made to the power source

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T13:11:13Z

Bensen: /* Fabrication of C-shaped electromagnet */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Then we will observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
[[File:C-shaped Electromagnet.jpg|thumb|200px|C-shaped Electromagnet]]
[[File:Copper coil wrapping.jpeg|thumb|200px|non-grain oriented electrical steel]]
# The main components of the electromagnet we are building are non-grain oriented electrical steel, by using laser beam, we cut the C-shaped piece out of the steel plate. After that, we accumulate all the pieces that we cut, forming ... cm thick. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')
# Then we use copper wiles to entwine each pole of the steel, ..., number of coils required for generating ... radio frequency pulse is according to the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* <math>B=2\mu_0nI</math>
#** <math>\mu_0=4\pi\times10^{-7}(\text{T}\cdot\text{m}/A)</math>
#** n is the number of loops per unit length of the solenoid (<math>n=\frac{N}{L}</math>, with N being the number of loops and L the length)
# Next, connect the electromagnet we made to the power source

====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T13:06:50Z

Bensen: /* Procedure */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Then we will observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
[[File:C-shaped Electromagnet.jpg|thumb|400px|C-shaped Electromagnet]]
# The main components of the electromagnet we are building are non-grain oriented electrical steel, by using laser beam, we cut the C-shaped piece out of the steel plate. After that, we accumulate all the pieces that we cut, forming ... cm thick. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')
# Then we use copper wiles to entwine each pole of the steel, ..., number of coils required for generating ... radio frequency pulse is according to the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* <math>B=2\mu_0nI</math>
#** <math>\mu_0=4\pi\times10^{-7}(\text{T}\cdot\text{m}/A)</math>
#** n is the number of loops per unit length of the solenoid (<math>n=\frac{N}{L}</math>, with N being the number of loops and L the length)
# Next, connect the electromagnet we made to the power source
====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample<ref>Nuclear Magnetic Resonance[https://www.springer.com/gp/book/9780387962436]</ref><ref>Nuclear Magnetic Resonance Spectroscopy: An Introduction to Principles, Applications, and Experimental Methods, 2nd Edition[https://www.wiley.com/en-us/Nuclear+Magnetic+Resonance+Spectroscopy%3A+An+Introduction+to+Principles%2C+Applications%2C+and+Experimental+Methods%2C+2nd+Edition-p-9781119295280]</ref>
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T13:03:48Z

Bensen: /* Results */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''A0228747R''
**'''Email:''' ''[mailto:info@example.org e0675585@u.nus.edu]''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.
* Introduction of NMR:The phenomenon of nuclear magnetic resonance is based on the fact that nuclei of certain elements possess a spin angular momentum and an associated magnetic moment.some well-known magnetic nuclei, such as <math>^{1}H</math> and <math>^{31}P</math> were able to absorb radio frequency energy when placed in a magnetic field of a strength that was specific to the nucleus. Upon absorption, the nuclei begin to resonate and different atoms within a molecule resonated at different frequencies. For example, when such neclei are placed in a magnetic field, they can adopt one of a number of quantized orientations,each orientation corresponding to a particular energy level.Especially, The orientation with the lowest energy is the one in which the nuclear magnetic moment is most closely aligned with the external magnetic field while the orientation with the highest energy is the one in which the nuclear magnetic moment is least closely aligned with the magnetic field.
*Quantized orientations:It is a fundamental fact of physics that a spinning charged body produces a magnetic moment. Since a nucleus is positively charged, if it then has a spin angular momentum, <math>P</math>, its spinning will result in the rotation of the positive charge which may be compared to a current flowing in a circle. This would produce a magnetic field parallel to the spin axis, and the nucleus would have a magnetic moment,In quantum mechanics, the angular momentum P is given by the relationship

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Then we will observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
[[File:C-shaped Electromagnet.jpg|thumb|400px|C-shaped Electromagnet]]
# The main components of the electromagnet we are building are non-grain oriented electrical steel, by using laser beam, we cut the C-shaped piece out of the steel plate. After that, we accumulate all the pieces that we cut, forming ... cm thick. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')
# Then we use copper wiles to entwine each pole of the steel, ..., number of coils required for generating ... radio frequency pulse is according to the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* <math>B=2\mu_0nI</math>
#** <math>\mu_0=4\pi\times10^{-7}(\text{T}\cdot\text{m}/A)</math>
#** n is the number of loops per unit length of the solenoid (<math>n=\frac{N}{L}</math>, with N being the number of loops and L the length)
# Next, connect the electromagnet we made to the power source
====Procedure====
# Put our sample within the gap of the C-shaped electromagnet<ref>Solid-State NMR Spectroscopy Principles and Applications[https://onlinelibrary.wiley.com/doi/book/10.1002/9780470999394]</ref>
# Change the input radio frequency pulse to control the spin of the electrons within sample
# Use hall probe connected to sample to readout the result

==Results==
* Just finished fabricating the electromagnet, will continue using it to control the spins within solids.

==References==

Control over the atomic spins within certain molecules by NMR technique

2021-04-30T12:59:51Z

Bensen: /* Procedure */

File:Steel cutter.jpeg

2021-04-30T12:50:53Z

Bensen:

File:The magnet.jpg

2021-04-30T12:50:23Z

Bensen:

File:Resistance of the magnet.jpg

2021-04-30T12:50:01Z

Bensen:

File:Laser cutter.jpeg

2021-04-30T12:49:23Z

Bensen:

File:Test resistance.jpg

2021-04-30T12:48:14Z

Bensen:

File:Steel cutting.jpeg

2021-04-30T12:47:19Z

Bensen:

File:Raw material for steel core.jpeg

2021-04-30T12:46:13Z

Bensen:

File:Copper coil wrapping.jpeg

2021-04-30T12:45:37Z

Bensen:

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:15:27Z

Bensen: /* Qubit readout */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Setup====
[[File:Experimental Setup.jpg|thumb|400px|Experimental Setup]]
* As shown in figure

====Quantum simulator====
* The <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math> heterostructure is fabricated via mechanical exfoliation and aligned transfer method. The stacking sequence of the sample is checked using second harmonic generation (SHG)-based measurement and it is found to be AA stacking. The sample is loaded into a magnetocryostat to control the magnetic ﬁeld and sample temperature.

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations
* The polarization state of the excitation and collection is controlled using a combination of polarizer, quarter-wave plate, and half-wave plate.

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* The PL emission is directed by a multimode optical ﬁber into a spectrometer (Andor Shamrock) with a CCD detector for spectroscopic recording

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:14:42Z

Bensen: /* Qubit initialisation */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Setup====
[[File:Experimental Setup.jpg|thumb|400px|Experimental Setup]]
* As shown in figure

====Quantum simulator====
* The <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math> heterostructure is fabricated via mechanical exfoliation and aligned transfer method. The stacking sequence of the sample is checked using second harmonic generation (SHG)-based measurement and it is found to be AA stacking. The sample is loaded into a magnetocryostat to control the magnetic ﬁeld and sample temperature.

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations
* The polarization state of the excitation and collection is controlled using a combination of polarizer, quarter-wave plate, and half-wave plate.

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:14:06Z

Bensen: /* Qubit initialisation */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Setup====
[[File:Experimental Setup.jpg|thumb|400px|Experimental Setup]]
* As shown in figure

====Quantum simulator====
* The <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math> heterostructure is fabricated via mechanical exfoliation and aligned transfer method. The stacking sequence of the sample is checked using second harmonic generation (SHG)-based measurement and it is found to be AA stacking. The sample is loaded into a magnetocryostat to control the magnetic ﬁeld and sample temperature.

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations
# The polarization state of the excitation and collection is controlled using a combination of polarizer, quarter-wave plate, and half-wave plate.

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:12:54Z

Bensen: /* Quantum simulator */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Setup====
[[File:Experimental Setup.jpg|thumb|400px|Experimental Setup]]
* As shown in figure

====Quantum simulator====
* The <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math> heterostructure is fabricated via mechanical exfoliation and aligned transfer method. The stacking sequence of the sample is checked using second harmonic generation (SHG)-based measurement and it is found to be AA stacking. The sample is loaded into a magnetocryostat to control the magnetic ﬁeld and sample temperature.

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:08:05Z

Bensen: /* Setup */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Setup====
[[File:Experimental Setup.jpg|thumb|400px|Experimental Setup]]
* As shown in figure

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

File:Experimental Setup.jpg

2021-03-21T05:07:27Z

Bensen:

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:06:38Z

Bensen: /* Setup */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Setup====
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* As shown in figure

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:05:23Z

Bensen: /* Experimental setup */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Setup====
* As shown in Fig.2

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T05:00:43Z

Bensen: /* Principle */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.
* However, valley optical selection rule in the heterobilayer TMDCs is a bit different than in the monolayer, which depends on the emission location and the emission energy. Additionally, in most cases, owing to the type II band alignment and weak hybridization, the conduction band minimum and valence band maximum of the van der Waals heterostructure are dominated by orbitals from different layers. As a result, electrons and holes tend to reside in different layers of the structure.
* It was found that the g-factor value of the interlayer exciton depends on the stacking sequence of the layers. For the AA-stacked <math>\text{MoSe}_2</math>/<math>\text{WSe}_2</math>, the value of the singlet g-factor between 6 to 7 has been reported; while, for the AB-stacked <math>\text{WSe}_2</math>/<math>\text{MoSe}_2</math>, the value of g-factor ~ −15 has been reported

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T03:45:26Z

Bensen: /* Choose monolayer TMDCs materials or 2D heterostructure? */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Why choose heterobilayer TMDCs instead of monolayer===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T03:44:42Z

Bensen: /* Description */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley pseudospin on 2D heterobilayer TMDCs.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-21T03:37:19Z

Bensen: /* Description */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After several decades of active research on the properties of TMDCs, some interesting features have been discovered. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley qubits.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-18T12:49:29Z

Bensen: /* Qubit initialisation */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After people took a deeper look at the properties of TMDCs, some interesting features have been found. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley qubits.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====
* Use circularly polarised light to create valley exciton polarization
* Use linearly polarised light to pump the qubits to rotate the valley pseudospin in the superposition plane of K and K′ valley polarizations

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-18T12:38:55Z

Bensen: /* Qubit control */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After people took a deeper look at the properties of TMDCs, some interesting features have been found. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley qubits.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====

====Qubit control====
* Most popular control techniques these days
*# 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.
*# 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-18T12:14:37Z

Bensen: /* Group members */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU (Bensen)'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After people took a deeper look at the properties of TMDCs, some interesting features have been found. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley qubits.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====

====Qubit control====
* 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.

* 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Control over the atomic spins within certain molecules by NMR technique

2021-03-18T12:14:01Z

Bensen: /* Group members */

Optical control of TMDCs valley pseudospin qubits

2021-03-18T10:48:32Z

Bensen: /* Qubit readout */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After people took a deeper look at the properties of TMDCs, some interesting features have been found. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley qubits.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====

====Qubit control====
* 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.

* 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====
* polarization of the photoluminescence

==Results==

==References==
<references />

Control over the atomic spins within certain molecules by NMR technique

2021-03-18T06:19:53Z

Bensen: /* Linked project */

==Linked project==
* This project is conducted by the same people as 👉 [[Optical control of TMDCs valley pseudospin qubits]]

==Group members==
*'''XU ZIZHOU'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==
* NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on. Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.

==Method==

===Principle===
We aim to use the C-shaped electromagnet that we build, to send magnetic pulse to the solid sample, which is between the poles of the magnet. Then we will observe the reaction of the sample to see if we can control the electron spin direction within it.

===Experimental setup===

====Fabrication of C-shaped electromagnet====
[[File:C-shaped Electromagnet.jpg|thumb|400px|C-shaped Electromagnet]]
# The main components of the electromagnet we are building are non-grain oriented electrical steel, by using laser beam, we cut the C-shaped piece out of the steel plate. After that, we accumulate all the pieces that we cut, forming ... cm thick. (''Note that the gap between two poles should be ... mm, as long as suitable enough to put sample in'')
# Then we use copper wiles to entwine each pole of the steel, ..., number of coils required for generating ... radio frequency pulse is according to the formula below:
#* <math>B=I\cdot\mu_0\frac{\mu_r}{L+d\cdot\mu_r}</math>
#** <math>\mu_0</math> is the permeability of free space
#** <math>\mu_r</math> is the relative permeability
#** <math>L</math> is the length of the magnet
#** <math>d</math> is the gap between two poles
#** <math>B</math> is the magnetic flux density (Tesla or <math>Wb/m^2</math>)
#* <math>B=2\mu_0nI</math>
#** <math>\mu_0=4\pi\times10^{-7}(\text{T}\cdot\text{m}/A)</math>
#** n is the number of loops per unit length of the solenoid (<math>n=\frac{N}{L}</math>, with N being the number of loops and L the length)
# Next, connect the electromagnet we made to the power source
====Procedure====
# Put our sample within the gap of the C-shaped electromagnet...
# Change the input radio frequency pulse to control the spin of the electrons within sample
# Use hall probe connected to sample to readout the result

==Results==

==References==

Main Page

2021-03-18T06:17:05Z

Bensen: /* Optical control of qubits built on quantum simulator */

Project wiki for the Module QT5201U (Quantum control technology) - AY20/21S2

Welcome to the wiki project page. This will be the place for documenting projects. To be able to write something to this wiki, we need to create a user login manually. If you have not yet created an account, do let me know - Christian.

==Project proposals==
===[[Wavemeter based on interferometer]]===
Basically we are now trying to build a wavemeter which can measure wavelength from 1200nm to 1800nm because the measurement tool for these lasers is not available now in our lab. It is based on Michelson interferometer.
===[[Coincidence Time Measurement of Pulsed Lasers & "Useful" Applications]]===
Proof-of-concept experiment to show how one may use commonly-available materials to measure difference in laser path lengths to sub-millimeter precision with a copper target (TBC). This experiment is done using a 355nm, 120 MHz, 10ps pulsed laser. Upon showing that such a measurement is possible, we shall go on to explore some for-fun applications of this "technology" and see how far and precise we can get.

===[[Saturated Absorption Spectroscopy + Frequency Modulation Locking on the D2 line of Rubidium 87]]===
With a combination of the Saturation Spectroscopy and Frequency Modulation techniques, we aim at stabilizing the wavelength of a Diode Laser at approximately 780.241 nm which corresponds to the transition <math>5S_{1/2} \rightarrow 5P_{3/2}</math> (also known as D2 line) of Rubidium 87. Additionally we will implement in the experiment a Red Pitaya, which is a minicomputer capable of replacing things like an Oscilloscope, Function Generator and PID controller. Therefore reducing the space needed for the experiment.

===[[Control over the atomic spins within certain molecules by NMR technique]]===
NMR has been the workhorse for the experimental implementation of quantum protocols, allowing exquisite control of systems up to seven qubits in size. However, there exists some experimental limitations in terms of the cross-talk, coupled evolution, instrumental errors and so on.
Thanks to the current advanced pulse techniques, we can reduce these influences and extend this technique to a new stage that the experimental limits can be neglected. In this experiment, we try to use composite pulses to compensate RF field strength variations and frequency offsets.

===[[Optical control of TMDCs valley pseudospin qubits]]===
Quantum dots or single electron transistors, allow for individual control of single charge or spin. In addition, some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers. Therefore, we try to adopt the method of this theoretical paper, and see if we can control single qubit or couple 2 qubits optically.

===[[A temperature-tunable etalon for optical telecommunication wavelength]]===
This project aims to build a Fabry-perot interferometer (also called Etalon) that works at the optical telecommunication wavelengths (1260nm-1625nm). This depicted etalon is made out of a single piece of polished silicon wafer with a thickness of about 100μm. The free spectral range (FSR) of the etalon can be adjusted by changing its thickness through temperature tuning. We will also explore the possibility of applying highly reflective (HR) coatings to the silicon wafer to achieve a high cavity finesse and a narrow transmission line-width.

===[[Microwave control of superconducting cavity and qubit]]===
This project aims to perform a trial pre-experiment based on the cQED architecture including simulation, calibration, microwave control pulse programming, and so on. The 3D superconducting cavity sample is anchored to the MXC flange inside the Bluefors dilution refrigerator to reach a temperature of around 10mK. On the other hand, the generation of microwave control pulses and the acquisition of output signals are handled by a QM quantum control device, connecting the sample via the control lines and the output lines accordingly. Hence, we can realize several bosonic states via cavity driving and qubit control.

===[[Laminar Air Flow-Based Acusto-Optical Modulator]]===
'''Not an active project! Just a random idea, might be fun to try.''' As discussed during the AOM lecture, a media with a slow speed of sound is preferred for construction of AOMs. The most common material through which the speed of sound is very very slow would be air. Unfortunately, atmospheric air by itself is very chaotic and is not optimal for use in the context of an AOM. Given these considerations, is it possible for a small chamber of a laminar flow of air, modulated by some acoustic frequency, act as an effective AOM?

==Material requests==
Please add stuff we should organize one way or the other here:
* more space
* cookies...

==Stuff to be covered in the lecture slots on Mondays (sometimes Tuesdays as well)==
Feel free to add topics or aspects to this list. At the moment, this is just a copy of the tentative syllabus:

{| class="wikitable"
!Date !! Topic !! Description

|-
| 18.1.2021
|[https://youtu.be/vDIOn2SHLJE Paraxial optics, part 1]
| rowspan = "2" | Optical systems often work with Gaussian beams. We cover practical design techniques like the ABCD matrix formalism for simple optical systems.
|-
| 19.1.2021
|[https://youtu.be/yO3JcuCOVoc Paraxial optics, part 2] (only first part of lecture)
|-
| 25.1.2021||[https://youtu.be/nNU1eEOaPdY Optical cavities, part 1] || Many optical techniques require to work with optical cavities. We cover how to design them, and how to couple light into very basic devices. This lecture covered some theory basics.
|-
| 26.1.2021||[https://youtu.be/ekfhUi2JjFM Optical cavities, part 2]|| Some more aspects of optical cavities, and dielectric coatings for mirrors and such

|-
| 1.2.2021||[https://youtu.be/h2LeznCpPTk Optical fiber technology] || Some properties of optical fibers as the most common optical waveguide are covered, including optical mode spectrum, dispersion and transmission properties.

|-
| 8.2.2021||[https://youtu.be/xblN-KzMz0Y Optical modulators, part 1]
| rowspan = "2" | Many optical modulation techniques require rely on devices or materials where optical properties can be changed electrically; we cover accousto-optical and electro-optical devices, as well as liquid crystal systems.
|-
| 9.2.2021||[https://youtu.be/WfP5mahZrWU Optical modulators, part 2]

|-
| 15.2.2021
|[https://youtu.be/m_F4DOHMNeU Homodyne detection techniques] || Measurement of optical fields in many continuous variable scenarios require knowledge of optical homodyning and heterodyning techniques. These techniques, similar to their radiofrequency counterparts, rely on multiplying field amplitudes.

|-
| 1.3.2021
|[https://youtu.be/YkVlxxucLuA Frequency control of laser systems, part 1]
| rowspan="2" |Many laser systems in quantum technologies require to have a well-defined frequency relationship with atomic transitions or solid state qubits. We cover typical techniques how laser systems can be controlled to a high enough accuracy, utilizing spectroscopy techniques and control systems.
|-
| 2.3.2021
|[https://youtu.be/72aVZwI4BHU Frequency control of laser systems, part 2]

|-
| 8.3.2021
|[https://youtu.be/jolUa_EGZEs Interface to computers]
| High level interfacing between computers and electronic hardware: Standard device languages; some serial protocols, some aspects of microcontrollers and FPGAs

|-
| 15.3.2021
|[https://youtu.be/1S0EAnooQMc Pulses in quantum control]
| Many quantum systems require short control pulses, either in form of optical pulses or radiofrequency pulses. This covers how they are used, and present a few techniques to generate such control pulses

|-
| ||Practical aspects of superconducting systems || We cover different materials, transition temperatures, temperature measurement techniques and thermal insulation / conduction techniques.

|-
| ||High voltage techniques || Working with high voltages requires a spectrum of techniques that is differing from more conventional electronics. A few aspects (field emission, dielectric strength, specific components) are covered.

|}

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Optical control of qubits built on quantum simulator

2021-03-18T06:16:24Z

Bensen: Bensen moved page Optical control of qubits built on quantum simulator to Optical control of TMDCs valley pseudospin qubits

#REDIRECT [[Optical control of TMDCs valley pseudospin qubits]]

Optical control of TMDCs valley pseudospin qubits

2021-03-18T06:16:19Z

Bensen: Bensen moved page Optical control of qubits built on quantum simulator to Optical control of TMDCs valley pseudospin qubits

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After people took a deeper look at the properties of TMDCs, some interesting features have been found. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley qubits.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====

====Qubit control====
* 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.

* 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====

==Results==

==References==
<references />

Optical control of TMDCs valley pseudospin qubits

2021-03-17T14:54:30Z

Bensen: /* Principle */

==Linked project==
* This project is conducted by the same people as 👉 [[Control over the atomic spins within certain molecules by NMR technique]]

==Group members==
*'''XU ZIZHOU'''
**'''Matric Number:''' ''A0229645W''
**'''Email:''' ''[mailto:info@example.org zizhou_xu@u.nus.edu]''
*'''CHU WENHAO'''
**'''Matric Number:''' ''...''

==Description==

* The strategies and materials for building universal quantum computers are being actively researched, and various platforms for holding qubits have been proposed and tested<ref>Experimental perfect state transfer of an entangled photonic qubit[https://www.nature.com/articles/ncomms11339]</ref><ref>Superconducting Qubits: Current State of Play[https://www.annualreviews.org/doi/abs/10.1146/annurev-conmatphys-031119-050605]</ref><ref>Two-qubit entangling gates within arbitrarily long chains of trapped ions[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022332]</ref><ref>Digital Coherent Control of a Superconducting Qubit[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.014009]</ref><ref>Fast quantum logic gates with trapped-ion qubits[https://www.nature.com/articles/nature25737]</ref>. Within all the options such as superconducting qubits and ion trap qubits, solid-state qubits have illustrated great benefits of the compatibility with the existing semiconductor technology, which attracts lots of attention to this platform. Moreover, because of the direct band gap and strong spin-orbit coupling discovered in the monolayer transition metal dichalcogenides (TMDCs), especially some semiconductor monolayers possess a sizeable direct bandgap of ≈1.5–2 eV in the optical range allowing electrostatic confinement and optical manipulation of carriers<ref>Atomically Thin MoS2: A New Direct-Gap Semiconductor[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.136805]</ref><ref>Emerging Photoluminescence in Monolayer MoS2[https://pubs.acs.org/doi/10.1021/nl903868w]</ref>, chances are TMDCs materials have the potential to become the promising platform for fabricating qubits. There are four main types of TMDCs that have been suggested as advantageous in acting qubits, <math>\text{WS}_2</math> , <math>\text{WSe}_2</math> , <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> . Kormányos et al used DFT calculations to confirm that <math>\text{WS}_2</math> and <math>\text{WSe}_2</math> , are better than <math>\text{MoS}_2</math> and <math>\text{MoSe}_2</math> in terms of the spin-valley coupling<ref>Spin-Orbit Coupling, Quantum Dots, and Qubits in Monolayer Transition Metal Dichalcogenides[https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.011034]</ref>, which is really important since spin-valley coupling is regarded as a key factor that can improve the coherence lifetime of spin-valley states.

* After people took a deeper look at the properties of TMDCs, some interesting features have been found. Such as the extra degree of freedom offered by valley magnetic moment, which can realise bit 0 and bit 1 to form a qubit in momentum space. In addition, these valleys are independently addressable by an optical signal, and optical controlling technique is currently under research by many groups both theoretically and experimentally. As a result, as inspired by the idea from one of the theoretical work<ref>Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.045313]</ref>, we intend to build a quantum simulator and investigate optical control of the spin-valley qubits.

==Q & A==

===What are K & K' points?===
[[File:K_&_K'_points.png|thumb|400px|K & K' points]]
* K-points are sampling points of Brillouin zone in reciprocal lattice
* The monolayer TMDs have a unique band structure with the conduction and valence band edges both at the degenerate K and K‘ valleys at the corners of the hexagonal Brillouin zone. The direct-gap optical transitions have a selection rule: left- (right-) handed circular polarized photons couple to the interband transitions in the K (K’) valley only

===Choose monolayer TMDCs materials or 2D heterostructure?===
* There are four main carrier properties that optimal Opto-valleytronics should possess.
*# long carrier lifetime
*# long valley lifetime
*# high valley polarization
*# long valley coherence time
* By adopting 2D heterostructure TMDCs materials, we can create these conditions for building promising quantum platform. (eg. Due to the type II band alignment and weak hybridization of van der Waals heterostructure, the electron–hole layer separation, the electron–hole exchange interaction is greatly reduced, resulting in a long cryogenic lifetime (ns to <math>\mu</math>s)and valley lifetime (~ 10 ns) of the interlayer exciton<ref>Opto-valleytronics in the 2D van der Waals heterostructure[https://doi.org/10.1007/s12274-020-3036-x]</ref>)

==Method==
===Principle===
* It was shown that inversion symmetry breaking can lead to opposite circular dichroism in different momentum space regions, which induces an interesting phenomena of optical selection rules at the symmetry corner points of the Brillouin zone. This enables a valley-dependent control of electrons with optical signal of different circular polarizations.

===Experimental setup===

====Quantum simulator====
* We intend to use WSe2 2D heterostructure encapsulated in hexagonal boron nitride (h-BN) as the physical platform, and ...

====Qubit initialisation====

====Qubit control====
* 1st approach: The coupling between the optical (electromagnetic) signal and the valley information can also be used to control the valley information. For the intralayer exciton, the exciton can be moved from one valley to another by applying intense THz radiation. This is shown by the observation of linearly polarized emission from higher-order sidebands when the sample is excited with a 100-fs near-resonant circularly polarized light pulse together with a 33-fs 40-THz pulse. Theoretically, it is shown that this is caused by a THz pulse driven intervalley transition. It is also predicted that a complete transfer from K (K’) to K’ (K) valley can be done within a period less than 5 fs if a more intense and shorter THz pulse is used.

* 2nd approach: On the other hand, by utilizing the optical Stark effect, the phase control has been demonstrated. In this case, the valley state is first prepared in the <math>|K\rang+|K'\rang</math> state by using a near-resonant linearly polarized excitation. A red-detuned 100-fs circularly polarized light pulse is then used to break the valley degeneracy, which allows the coherent rotation of the valley state to the <math>|K\rang+e^{i\Delta\phi}|K'\rang</math> state with <math>\Delta\phi</math> depends on the pulse intensity and duration. This rotation is reflected in the linear polarization state of the exciton emission.

====Qubit readout====

==Results==

==References==
<references />