Photon number resolving methods and systems
A photon-number resolving (PNR) method and system are described. A PNR detector is calibrated to generate a characteristic pulse plot for each of a plurality of unique photon numbers. A generic tail portion is also stored. A signal is then detected through the PNR detector. The signal includes at least a first pulse and a second pulse, where the second pulse at least partially overlaps with the first pulse. The first photon number of the first pulse may be determined. Then, the characteristic pulse plot that corresponds to the first photon number is subtracted from the first pulse, such that the second photon number of the second pulse may be determined with minimized interference from any signal overlap. The generic tail portion may be scaled and subtracted from any identified stray events to minimize interference of stray signals from unintended light sources.
1. A photon-number resolving (PNR) method comprising:
calibrating a PNR detector to generate a characteristic pulse plot for each of a plurality of photon numbers;
receiving, by the PNR detector, a signal including a first pulse and a second pulse, where the second pulse at least partially overlaps with the first pulse;
determining a first photon number of the first pulse;
subtracting a characteristic plot that corresponds to the first photon number from the first pulse of the received electrical signal plot;
determining a second photon number of the second pulse; and
storing the first and second photon numbers.
2. The PNR method of claim 1 , further includes performing stray tail subtraction.
3. The PNR method of claim 2 , wherein the stray tail subtraction is performed before the determining of the first photon number.
4. The PNR method of claim 2 , wherein the stray tail subtraction is performed before the determining of the second photon number.
5. The PNR method of claim 2 , wherein performing stray tail subtraction includes:
determining a stray event; and
reducing disturbance caused by the stray event by subtracting a tail portion obtained from the characteristic wave plots from the received signal.
6. The PNR method of claim 5 , wherein the determining of the stray tail event includes:
determining a standard deviation of a 0-photon number state of the received signal; and
identifying a stray event when value of the received signal exceeds a threshold value.
7. The PNR method of claim 5 , wherein the tail portion is a second half of a 2-photon number characteristic plot.
8. The PNR method of claim 5 , further includes:
scaling the tail portion by an offset value.
9. The PNR method of claim 8 , wherein the offset value is determined by:
determining a mean value of the received signal;
determining a mean value of a 0 photon number characteristic plot; and
setting the offset value as a difference between the mean value of the received signal and the mean value of the 0 photon number characteristic plot.
10. The PNR method of claim 1 , wherein the characteristic pulse plot for each of the plurality of photon numbers are generated from a high number of low repetition rate pulses received at the PNR detector.
11. The PNR method of claim 1 , wherein determining the first photon number includes area method, principal component analysis (PCA), and dot product method.
12. The PNR method of claim 1 , wherein determining the second photon number includes area method, principal component analysis (PCA), and dot product method.
13. The PNR method of claim 1 , wherein the first and second pulses are spaced apart by Δt in time domain such that the PNR detector operates in a linear response region.
14. A photon number resolving (PNR) system comprising:
a PNR detector configured to detect photons in a pulse of light generated from a light source;
a signal processor configured to:
calibrate the PNR detector to generate a characteristic pulse plot for each of a plurality of photon numbers;
receive a detected signal from the PNR detector including a first pulse and a second pulse, where the second pulse at least partially overlaps with the first pulse;
determine a first photon number of the first pulse;
subtract a characteristic plot that corresponds to the first photon number from the first pulse of the received electrical signal plot;
determine a second photon number of the second pulse; and
store the first and second photon numbers.
15. The PNR system of claim 14 , wherein the PNR detector is a transition-edge sensor (TES) based PNR detector.
16. The PNR system of claim 14 further comprises a data acquisition system (DAQ) configured to detect and record the detected signal from the PNR detector, wherein the DAQ further comprises an amplifier configured to amplify the detected signal from the PNR detector.
17. The PNR system of claim 14 , wherein the signal processor is further configured to perform stray tail subtraction before determining the first photon number and before determining the second photon number.
18. The PNR system of claim 17 , wherein to perform the stray tail subtraction, the signal processor is configured to:
determine a stray event; and
reduce disturbance caused by the stray event by subtracting a tail portion obtained from the characteristic wave plots from the received signal.
19. The PNR system of claim 18 , wherein to determine the stray tail event, the signal processor is further configured to:
determine a standard deviation of a 0-photon number state of the received signal; and
identify a stray event when value of the received signal exceeds a threshold value.
20. The PNR system of claim 18 , wherein the signal processor is further configured to scale the tail portion by an offset value, wherein the offset value is determined by:
determine a mean value of the received signal;
determine a mean value of a 0-photon number characteristic plot; and
setting the offset value as a difference between the mean value of the received signal and the mean value of the 0-photon number characteristic plot.