QT5201U wiki - User contributions [en]

Time-bin QKD

2026-10-24T07:39:57Z

Ziyan: /* 2026-10-19 */

'''Team Members''': Wang Ziyan, Wu Jinbin

== Summary ==
The project is to implement time-bin QKD on the encoding and decoding ends.

== Theoretical Background ==

== List of Equipment ==

{| class="wikitable"
|-
! Equipment !! Manufacturers !! Quantities
|-
| Function Generator AFG1022 || Tektronix, Inc || 1
|-
| Oscilloscope HDO6104 || Teledyne LeCroy || 1
|-
| NIM FAN-OUT Module || S-Fifteen Instruments || 1
|-
| NIM Anti-coincidence Module || S-Fifteen Instruments || 2
|-
| NIM cables || || multiples
|-
| BNC cables || || multiples
|}

== Experiment Setup ==

=== 1. Producing a short pulse ===

The shortest pulse that can be generated by the function generator is about 40 nanoseconds, which is too long for our purpose. To create a shorter pulse, we performed pulse shortening using delayed Anti-Coincidence Logic.

A short electrical pulse was first generated using function generator with high level as 0V and low level as -1.0V, following NIM (Nuclear Instrumentation Module) Standard.

The input pulse was first passed through a fanout module to produce two identical copies, B and B'. A relative time delay, <math>\Delta t</math>, was introduced between the two signals before they were sent to the signal and veto inputs of the anti-coincidence module. The anti-coincidence module produces an output only when B is present while the delayed signal B' is absent. This operation can be represented as

<math> V_{out} = B \land \overline{B'}</math>.

When the leading edge of B arrives, the output becomes high. After a delay <math>\Delta t</math>, the leading edge of B' reaches the veto input and suppresses the output. Consequently, the original pulse is converted into a much shorter pulse whose width is approximately determined by the relative delay:

<math>T_{\mathrm{pulse}}\approx \Delta t</math>.

Thus, by controlling the delay between the two copies of the input signal, the output pulse width can be adjusted independently of the width of the original pulse. The short pulse is generated at the rising edge of the input signal.

=== 2. Finding the operating current of the laser diode ===

== Experiment Record ==

=== 2026-10-5 ===
1. Prof. Kurtsiefer explained the principles of experiments and the experimental apparatuses.

2. We learned how to use Oscilloscope HDO6104.

=== 2026-10-6 ===
1. We used the Function Generator AFG1022 to generate a short pulse that followed NIM Standard and had a width of about 40ns. The rise time (10% to 90%) of the pulse is approximately 2ns.

2. A NIM FAN-OUT Module was used to split the short pulse into two identical NIM pulses, with the rise time (10% to 90%) decreased to about 780ps.

3. The two identical NIM pulse were sent to the signal and veto ports of an NIM Anti-coincidence Module respectively, producing an output pulse with a width of about 2ns. The rise time of the pulse is about 780ps.

=== 2026-10-14 ===
1. The same as before, we used the Function Generator AFG1022 to generate a short pulse and then inputted the pulse into the NIM FAN-OUT Module.

2. We measured the three output ports and obtained three rise times (10% to 90%), thich are respectively 800ps, 760ps and 720ps.

3. In order to obtain the best signal, we inputted the pulse with the shortest rise time to the "signal" port, and the pulse with the second shortest rise time to the "veto" port. Then we got an output pulse with a width of about 1ns.

4. We connected the laser diode to the function generator and output square waves. The laser diode started emitting light form a 0.5-volt high level.

5. We measured the battery voltage to be 9.47 volts. This is much higher than the operating voltage range of the laser diode, so it cannot be used as a DC power supply.

=== 2026-10-19 ===
1. We connected the battery (the 9.47-volts one), the photodiode and a resistor (9.959 kOhm) in series together. And we used a voltmeter to measure the voltage of this resistor.

2. We connected a laser diode to the direct current power supply, and gradually increased the output voltage. The laser diode begined to emit red light that can be observed with the naked eye at about 1.65V.

3. We aligned the illuminated area with the sensor region of the photodiode. When the output voltage of DC supply was 0V, we read the voltage display value 11.80mV and recorded it as the ambient voltage (dark current is included in it).

4. Starting from 1.60V and gradually increasing, we read the voltage values from the voltmeter every 0.5V and recorded them.

5. After subtracting the ambient voltage from the measured voltage and then dividing by the resistance, we obtained the photocurrent from the laser diode. Then we divede these photocurrent datas by response in 780nm (temporally consider the red light from laser diode is 780nm), and we obtained the power of the laser diode.

6. We draw a graph showing the output power of the laser diode in relation to the input voltage.

== Result and Discussion ==

== Conclusion ==

Time-bin QKD

2026-10-24T07:38:16Z

Ziyan: /* Experiment Record */

Time-bin QKD

2026-10-24T07:02:40Z

Ziyan: /* Experiment Setup */

'''Team Members''': Wang Ziyan, Wu Jinbin

== Summary ==
The project is to implement time-bin QKD on the encoding and decoding ends.

== Theoretical Background ==

== List of Equipment ==

{| class="wikitable"
|-
! Equipment !! Manufacturers !! Quantities
|-
| Function Generator AFG1022 || Tektronix, Inc || 1
|-
| Oscilloscope HDO6104 || Teledyne LeCroy || 1
|-
| NIM FAN-OUT Module || S-Fifteen Instruments || 1
|-
| NIM Anti-coincidence Module || S-Fifteen Instruments || 2
|-
| NIM cables || || multiples
|-
| BNC cables || || multiples
|}

== Experiment Setup ==

=== 1. Producing a short pulse ===

The shortest pulse that can be generated by the function generator is about 40 nanoseconds, which is too long for our purpose. To create a shorter pulse, we performed pulse shortening using delayed Anti-Coincidence Logic.

A short electrical pulse was first generated using function generator with high level as 0V and low level as -1.0V, following NIM (Nuclear Instrumentation Module) Standard.

The input pulse was first passed through a fanout module to produce two identical copies, B and B'. A relative time delay, <math>\Delta t</math>, was introduced between the two signals before they were sent to the signal and veto inputs of the anti-coincidence module. The anti-coincidence module produces an output only when B is present while the delayed signal B' is absent. This operation can be represented as

<math> V_{out} = B \land \overline{B'}</math>.

When the leading edge of B arrives, the output becomes high. After a delay <math>\Delta t</math>, the leading edge of B' reaches the veto input and suppresses the output. Consequently, the original pulse is converted into a much shorter pulse whose width is approximately determined by the relative delay:

<math>T_{\mathrm{pulse}}\approx \Delta t</math>.

Thus, by controlling the delay between the two copies of the input signal, the output pulse width can be adjusted independently of the width of the original pulse. The short pulse is generated at the rising edge of the input signal.

=== 2. Finding the operating current of the laser diode ===

== Experiment Record ==

=== 2026-10-5 ===
1. Prof. Kurtsiefer explained the principles of experiments and the experimental apparatuses.

2. We learned how to use Oscilloscope HDO6104.

=== 2026-10-6 ===
1. We used the Function Generator AFG1022 to generate a short pulse that followed NIM Standard and had a width of about 40ns. The rise time (10% to 90%) of the pulse is approximately 2ns.

2. A NIM FAN-OUT Module was used to split the short pulse into two identical NIM pulses, with the rise time (10% to 90%) decreased to about 780ps.

3. The two identical NIM pulse were sent to the signal and veto ports of an NIM Anti-coincidence Module respectively, producing an output pulse with a width of about 2ns. The rise time of the pulse is about 780ps.

=== 2026-10-14 ===
1. The same as before, we used the Function Generator AFG1022 to generate a short pulse and then inputted the pulse into the NIM FAN-OUT Module.

2. We measured the three output ports and obtained three rise times (10% to 90%), thich are respectively 800ps, 760ps and 720ps.

3. In order to obtain the best signal, we inputted the pulse with the shortest rise time to the "signal" port, and the pulse with the second shortest rise time to the "veto" port. Then we got an output pulse with a width of about 1ns.

4. We connected the laser diode to the function generator and output square waves. The laser diode started emitting light form a 0.5-volt high level.

5. We measured the battery voltage to be 9.47 volts. This is much higher than the operating voltage range of the photondiode, so it cannot be used as a DC power supply.

=== 2026-10-19 ===
1. We used the Function Generator AFG1022 to generate a short pulse that followed NIM Standard and had a width of about 40ns. The rise time (10% to 90%) of the pulse is approximately 2ns.

2. A NIM FAN-OUT Module was used to split the short pulse into two identical NIM pulses, with the rise time (10% to 90%) decreased to about 780ps.

3. The two identical NIM pulse were sent to the signal and veto ports of an NIM Anti-coincidence Module respectively, producing an output pulse with a width of about 2ns. The rise time of the pulse is about 780ps.

== Result and Discussion ==

== Conclusion ==

Time-bin QKD

2026-10-24T06:59:35Z

Ziyan: /* Experiment Record */

'''Team Members''': Wang Ziyan, Wu Jinbin

== Summary ==
The project is to implement time-bin QKD on the encoding and decoding ends.

== Theoretical Background ==

== List of Equipment ==

{| class="wikitable"
|-
! Equipment !! Manufacturers !! Quantities
|-
| Function Generator AFG1022 || Tektronix, Inc || 1
|-
| Oscilloscope HDO6104 || Teledyne LeCroy || 1
|-
| NIM FAN-OUT Module || S-Fifteen Instruments || 1
|-
| NIM Anti-coincidence Module || S-Fifteen Instruments || 2
|-
| NIM cables || || multiples
|-
| BNC cables || || multiples
|}

== Experiment Setup ==

=== 1. Producing a short pulse ===

The shortest pulse that can be generated by the function generator is about 40 nanoseconds, which is too long for our purpose. To create a shorter pulse, we performed pulse shortening using delayed Anti-Coincidence Logic.

A short electrical pulse was first generated using function generator with high level as 0V and low level as -1.0V, following NIM (Nuclear Instrumentation Module) Standard.

The input pulse was first passed through a fanout module to produce two identical copies, B and B'. A relative time delay, <math>\Delta t</math>, was introduced between the two signals before they were sent to the signal and veto inputs of the anti-coincidence module. The anti-coincidence module produces an output only when B is present while the delayed signal B' is absent. This operation can be represented as

<math> V_{out} = B \land \overline{B'}</math>.

When the leading edge of B arrives, the output becomes high. After a delay <math>\Delta t</math>, the leading edge of B' reaches the veto input and suppresses the output. Consequently, the original pulse is converted into a much shorter pulse whose width is approximately determined by the relative delay:

<math>T_{\mathrm{pulse}}\approx \Delta t</math>.

Thus, by controlling the delay between the two copies of the input signal, the output pulse width can be adjusted independently of the width of the original pulse. The short pulse is generated at the rising edge of the input signal.

== Experiment Record ==

=== 2026-10-5 ===
1. Prof. Kurtsiefer explained the principles of experiments and the experimental apparatuses.

2. We learned how to use Oscilloscope HDO6104.

=== 2026-10-6 ===
1. We used the Function Generator AFG1022 to generate a short pulse that followed NIM Standard and had a width of about 40ns. The rise time (10% to 90%) of the pulse is approximately 2ns.

2. A NIM FAN-OUT Module was used to split the short pulse into two identical NIM pulses, with the rise time (10% to 90%) decreased to about 780ps.

3. The two identical NIM pulse were sent to the signal and veto ports of an NIM Anti-coincidence Module respectively, producing an output pulse with a width of about 2ns. The rise time of the pulse is about 780ps.

=== 2026-10-14 ===
1. The same as before, we used the Function Generator AFG1022 to generate a short pulse and then inputted the pulse into the NIM FAN-OUT Module.

2. We measured the three output ports and obtained three rise times (10% to 90%), thich are respectively 800ps, 760ps and 720ps.

3. In order to obtain the best signal, we inputted the pulse with the shortest rise time to the "signal" port, and the pulse with the second shortest rise time to the "veto" port. Then we got an output pulse with a width of about 1ns.

4. We connected the laser diode to the function generator and output square waves. The laser diode started emitting light form a 0.5-volt high level.

5. We measured the battery voltage to be 9.47 volts. This is much higher than the operating voltage range of the photondiode, so it cannot be used as a DC power supply.

=== 2026-10-19 ===
1. We used the Function Generator AFG1022 to generate a short pulse that followed NIM Standard and had a width of about 40ns. The rise time (10% to 90%) of the pulse is approximately 2ns.

2. A NIM FAN-OUT Module was used to split the short pulse into two identical NIM pulses, with the rise time (10% to 90%) decreased to about 780ps.

3. The two identical NIM pulse were sent to the signal and veto ports of an NIM Anti-coincidence Module respectively, producing an output pulse with a width of about 2ns. The rise time of the pulse is about 780ps.

== Result and Discussion ==

== Conclusion ==

Time-bin QKD

2026-10-19T04:31:45Z

Ziyan: /* Experiment Record */

'''Team Members''': Wang Ziyan, Wu Jinbin

== Summary ==
The project is to implement time-bin QKD on the encoding and decoding ends.

== Theoretical Background ==

== List of Equipment ==

{| class="wikitable"
|-
! Equipment !! Manufacturers !! Quantities
|-
| Function Generator AFG1022 || Tektronix, Inc || 1
|-
| Oscilloscope HDO6104 || Teledyne LeCroy || 1
|-
| NIM FAN-OUT Module || S-Fifteen Instruments || 1
|-
| NIM Anti-coincidence Module || S-Fifteen Instruments || 2
|-
| NIM cables || || multiples
|-
| BNC cables || || multiples
|}

== Experiment Setup ==

=== 1. Producing a short pulse ===

The shortest pulse that can be generated by the function generator is about 40 nanoseconds, which is too long for our purpose. To create a shorter pulse, we performed pulse shortening using delayed Anti-Coincidence Logic.

A short electrical pulse was first generated using function generator with high level as 0V and low level as -1.0V, following NIM (Nuclear Instrumentation Module) Standard.

The input pulse was first passed through a fanout module to produce two identical copies, B and B'. A relative time delay, <math>\Delta t</math>, was introduced between the two signals before they were sent to the signal and veto inputs of the anti-coincidence module. The anti-coincidence module produces an output only when B is present while the delayed signal B' is absent. This operation can be represented as

<math> V_{out} = B \land \overline{B'}</math>.

When the leading edge of B arrives, the output becomes high. After a delay <math>\Delta t</math>, the leading edge of B' reaches the veto input and suppresses the output. Consequently, the original pulse is converted into a much shorter pulse whose width is approximately determined by the relative delay:

<math>T_{\mathrm{pulse}}\approx \Delta t</math>.

Thus, by controlling the delay between the two copies of the input signal, the output pulse width can be adjusted independently of the width of the original pulse. The short pulse is generated at the rising edge of the input signal.

== Experiment Record ==

=== 2026-10-5 ===
1. Prof. Kurtsiefer explained the principles of experiments and the experimental apparatuses.

2. We learned how to use Oscilloscope HDO6104.

=== 2026-10-6 ===
1. We used the Function Generator AFG1022 to generate a short pulse that followed NIM Standard and had a width of about 40ns. The rise time (10% to 90%) of the pulse is approximately 2ns.

2. A NIM FAN-OUT Module was used to split the short pulse into two identical NIM pulses, with the rise time (10% to 90%) decreased to about 780ps.

3. The two identical NIM pulse were sent to the signal and veto ports of an NIM Anti-coincidence Module respectively, producing an output pulse with a width of about 2ns. The rise time of the pulse is about 780ps.

=== 2026-10-14 ===
1. The same as before, we used the Function Generator AFG1022 to generate a short pulse and then inputted the pulse into the NIM FAN-OUT Module.

2. We measured the three output ports and obtained three rise times (10% to 90%), thich are respectively 800ps, 760ps and 720ps.

3. In order to obtain the best signal, we inputted the pulse with the shortest rise time to the "signal" port, and the pulse with the second shortest rise time to the "veto" port. Then we got an output pulse with a width of about 1ns.

4. We connected the photondiode to the function generator and output square waves. The photondiode started emitting light form a 0.5-volt high level.

5. We measured the battery voltage to be 9.47 volts. This is much higher than the operating voltage range of the photondiode, so it cannot be used as a DC power supply.

== Result and Discussion ==

== Conclusion ==

Time-bin QKD

2026-10-19T03:59:37Z

Ziyan: /* 2026-10-6 */

Time-bin QKD

2026-10-11T11:44:03Z

Ziyan:

Time-bin QKD

2026-10-11T11:43:42Z

Ziyan:

Time-bin QKD

2026-10-11T10:27:46Z

Ziyan:

Main Page

2026-09-27T14:13:19Z

Ziyan: /* Placehold for project title */

<strong>Wiki page for course QT5201U (Quantum control technology) - AY2026/27S1</strong>

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.

'''Next class:''' Mon 17 Aug 2026 in the seminar room S15 level 5.

==Project pages==
===[[Example project title]]===
One sentence, describing what this project is is about.

'''Team members:''' A, B, C

=== [[QKD receiver characterization (Polarization)]] ===

Calibrated polarization-state generator to characterize polarization analysis modules in QKD receivers and rigorously quantify the impact on secure key rates.

'''Team members:''' Elias X. Huber, various AI agents (open to join forces with other humans as well, you can reach me at elias.x.huber[at typical nus sufix]; please note though that I will likely do the experiment at UTown (CREATE Tower), my schedule tends to be a bit inflexible for team-work, and I am a theorist with no lab experience).

=== [[Control and measurement in the bosonic cQED system]] ===
Using control and measurement methods to characterize a dispersively coupled single superconducting cavity and single transmon qubit system, with a thorough review of the theories and experimental techniques behind it.

'''Team members:''' Grace Pang and Seungwon Jin

===[[Multi-tone RFSoC driver for an AOM]]===
A multi-tone RF synthesizer on an RFSoC board to drive an acousto-optic modulator(AOM).

'''Team members:''' Mani Aarthy

===[[Placeholder for project title]]===
TBD.
'''Team members''' Wang Ziyan and Wu Jinbin

===[[Laser Phase Offset Lock]]===
We plan to implement an offset lock to phase stabilize a pair of External Cavity Diode Lasers (ECDL) at a fixed offset of 6.8 GHz, matching the Rb87 ground state hyperfine transition.

'''Team members:''' Bibhuti Thapa, Xu Zifang, Chan Jun Jie

===[[Home-Built ECDL and Optical Sideband Generation]]===

The project includes the construction and characterization of a Littrow ECDL, microwave-driven EOM sideband generation near 6.8 GHz, and optical beat-note techniques for relative frequency stabilization with an existing Rb87 trapping laser.

'''Team member:''' Liu Yiming

===[[Thermal Drift Compensation via RF and DC Feedback for Thermal Device Control Applications]]===
We plan to calibrate a thermally tunable microring resonator, compensate TEC-induced thermal drift using DC feedback, and evaluate gesture-image reconstruction through the AC channel.

'''Team members:''' Huang He, Ding Jiahao, Xu Anbang

===[[Measurement of Coherent States in Phase Space]]===
'''Team members:''' Lim Zi Way, Raghav Sah, Shawn Liew Hong Wei

===[[Design and Construction of a Confocal Microscope for Photonic Material Characterization]]===
'''Team members:''' Kim Sihyung, Ankush Sharma, Liang Shuyi

==Resources==
Some hopefully useful references should go here.
===Recommended literature===
* Bahaa E. A. Saleh, Malvin Carl Teich: Fundamentals of Photonics, Wiley; available as [https://libproxy1.nus.edu.sg/login?url=https://search.ebscohost.com/login.aspx?direct=true&db=nlebk&AN=26193&site=ehost-live&ebv=EB&ppid=pp_Cover e-book in NUS]. Excellent reference book for many optics topics.
* Mark Fox: Quantum Optics: An Introduction, Oxford University Press; available as [https://libproxy1.nus.edu.sg/login?url=https://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=208564 e-book in NUS]. Nice book on traditional quantum optics topics.
* Christopher C. Davis: Lasers and electro-optics, Cambridge; available as [https://libproxy1.nus.edu.sg/login?url=https://dx.doi.org/10.1017/CBO9781139016629 e-book in NUS]. Good overall book on optics-related aspects useful for controlling quantum systems.

===Recorded classes===

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

|-
| 17.8.2026
| [https://youtu.be/tUuzyOVIlxk Paraxial ray optics]
| A recap of how to deal with classical ray optics through ABCD matrices
| Saleh, Teich: Fundamentals of Photonics

|-
| 18.8.2026
| [https://youtu.be/lSKFl8u21_w Paraxial wave optics]
| Working towards Gaussian beams found with lasers...
| same as above

|-
| 24.8.2026
| [https://youtu.be/2HZCak7ODlM Optical cavities 1]
| Fabry-Perot, simple 1D dimensional
|
|-

| 25.8.2026
| [https://youtu.be/GEa3ktnrMrg Optical cavities 2]
| Transverse mode structure, optical coating basics
|
|-

| 14.9.2026
| [https://youtu.be/Lwt6eJe12h0 Homo- and heterodyning basics]
| Radiofrequency origins of mixers, optical version
| any quantum optics text (e.g. Mark Fox, see above)
|-

| 15.9.2026
| [https://youtu.be/2nhP60FKstQ Optical Modularors 1]
| Mostly Electro-optical modulators, some LCD as well
| e.g. Davis: Laser and Electro-optics
|-

|}
Complete playlist: https://www.youtube.com/playlist?list=PLN-Fk1m9cTD4

==Previous version of this course wiki==
* AY2012S2: https://ay2021s2.qt5201.org

== Getting started ==
Consult the [https://www.mediawiki.org/wiki/Special:MyLanguage/Help:Contents User's Guide] for information on using the wiki software.
* [https://www.mediawiki.org/wiki/Special:MyLanguage/Manual:FAQ MediaWiki FAQ]
* Math can be entered in LaTeX style: <code><nowiki><math>r^2=\sqrt{x^2+y^2}</math></nowiki></code> renders as <math>r^2=\sqrt{x^2+y^2}</math>
* Should you miss any module or functionality of this wiki, please contact me (Christian Kurtsiefer).