Jitter calibration system and method for superconducting nanowire single-photon detector

Abstract

The invention discloses a jitter calibration system and method for a superconducting nanowire single-photon detector. Comprising an FPGA platform used for generating periodic pulse calibration signals, a radio frequency pulse amplifier, a lithium niobate electrooptical modulator and a bias voltage controller thereof, a 1550nm 3kHz linewidth distributed feedback laser, a program control optical attenuator, a three-paddle polarization controller, an SNSPD single photon detector, a multichannel TDC module and an upper computer used for processing data. The calibration method is simple and low in cost, can calibrate a correction curve of the relation between SNSPD detection photon additional jitter and detection recovery time caused by pulse accumulation, compensates additional jitter, and can effectively solve the problem of jitter deterioration generated by SNSPD under a high counting rate in high-speed detection application.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless optical communications, and relates to a jitter calibration system and method for a superconducting nanowire single-photon detector. Background Art

[0002] As a laser communication system with high sensitivity and low power requirements, photon counting communication is very suitable for deep space link scenarios. However, with the continuous development of deep space exploration missions, the detection distance and the amount of data transmitted have further increased, and the communication rate requirements for optical communication systems have become increasingly higher. Therefore, superconducting nanowire single photon detectors (SNSPDs) with advantages such as high detection efficiency (close to 100%), low dark counts (<10cps), small time jitter (tens of picoseconds @FWHM), and low blocking effect (recovery characteristic time of tens of nanoseconds) have gradually become a hot topic in deep space optical communication research.

[0003] For high-precision time measurement applications based on SNSPD, such as single-photon imaging, single-photon radar, quantum communication, and photon counting communication, the time domain jitter of the detected photons is an important factor that limits the timing resolution accuracy. Especially in high-speed photon counting communication applications, when the overall time domain jitter distribution of the detected photons overflows the time slot duration, the potential counting crosstalk between time slots will affect the accuracy of information recovery and communication synchronization. Therefore, its jitter performance participates in determining the upper limit of the time slot frequency and thus affects the maximum data transmission rate. In a typical detection photon arrival time distribution, it mainly includes the edge jitter and pulse width of the pulse laser source itself at the transmitting end, the jitter of the photon arrival time read out by the time-to-digital converter (TDC) at the receiving end, and the jitter from the SNSPD at the detection end. In high-speed applications, due to the characteristics of the detector itself, when the photon count rate is close to saturation, the TDC received photon arrival time jitter performance triggered by the single threshold discriminator will be significantly deteriorated due to the accumulation of detection pulses and incomplete recovery of superconducting current (the additional jitter half-maximum full width introduced usually reaches hundreds of picoseconds @FWHM), and it will also introduce asymmetry in the photon arrival time distribution. Figure 1 The SNSPD detection pulse waveform and the current recovery represented by blue are shown in the figure. The yellow timestamp represents the moment when the photon is responded to by the SNSPD, and the red and black timestamps represent the theoretical and actual moments when the TDC is triggered and the arriving photons are read out, respectively.

[0004] Currently, there are few solutions to this problem. The existing hardware method of using a constant fraction discriminator (CFD) instead of a single threshold trigger readout at the front end of the TDC to overcome the pile-up jitter is not suitable for multi-channel SNSPD expansion, especially the photon signal readout of large-scale SNSPD arrays, due to its complex structure and high cost. Therefore, a simple, low-cost, and effective software method is urgently needed to suppress the jitter deterioration problem of SNSPD at high count rates, so as to meet the needs of higher-precision time measurement applications. Summary of the invention

[0005] The purpose of the present invention is to provide a jitter calibration system and method for a superconducting nanowire single-photon detector. The calibration method is simple and low-cost. It can calibrate a correction curve of the relationship between the additional jitter of SNSPD detection photons caused by pulse pileup and the detection recovery time, and compensate for the additional jitter. It can effectively solve the jitter deterioration problem of SNSPD at high counting rates in high-speed detection applications.

[0006] The technical solution to achieve the purpose of the present invention is:

[0007] A jitter calibration device for a superconducting nanowire single-photon detector comprises an FPGA platform, wherein the FPGA platform is used to generate a periodic pulse calibration signal, and a first narrow pulse signal and another synchronous calibration signal are generated by respectively encoding two GT transceivers on the FPGA platform. The first narrow pulse signal is subjected to electro-optical conversion by a photoelectric conversion unit to generate a high-modulation extinction ratio narrow pulse laser signal with the same repetition rate and pulse width, which is connected to an SNSPD system after passing through an optical attenuation and bias controller to trigger the detector's response to a periodic photon-level signal. The detection pulse signal generated by a low-noise radio frequency amplifier is received via multiple channels of a multi-channel TDC module and a timestamp is read out; meanwhile, the other synchronous calibration signal has a period of 64 times that of the first narrow pulse signal, is directly connected to the multi-channel TDC module, and a timestamp is read out by an additional channel, and a host computer processes the timestamps received by the multi-channel TDC module and generates a correction curve for additional jitter.

[0008] In the preferred technical solution, the photoelectric conversion unit includes a radio frequency pulse amplifier, a lithium niobate electro-optical modulator and its bias voltage controller, and a 1550nm line width distributed feedback laser. The radio frequency pulse amplifier is connected to a GT transceiver of the FPGA platform. The radio frequency pulse amplifier is also connected to the lithium niobate electro-optical modulator. The lithium niobate electro-optical modulator is connected to the 1550nm line width distributed feedback laser and the modulator bias voltage controller.

[0009] In the preferred technical solution, the first narrow pulse signal is a narrow pulse signal with a repetition rate of 1.25 GHz and a pulse width of 200 ps, ​​and the other synchronous calibration signal is a synchronous calibration signal with a repetition rate of 9.53125 MHz and a pulse width of 1.5 ns.

[0010] The present invention also discloses a jitter calibration method for a superconducting nanowire single-photon detector, which is applied to the jitter calibration device mentioned above. The jitter calibration method comprises the following steps:

[0011] S01: Use the pulse signal with a pulse width of 1.5ns and a period of 51.2ns sent by the GT transceiver on the FPGA platform as the synchronous calibration signal of the laser pulse to collect the timestamp with a trigger threshold of 460mV on the multi-channel TDC module;

[0012] S02: equidistantly interpolate 63 data points between adjacent timestamps of the synchronous calibration signal as a 1.25 GHz synchronous calibration signal with the same frequency as the laser pulse;

[0013] S03: There is only a fixed delay ΔT0 between the interpolated synchronous calibration signal and the periodic photon pulse signal. The arrival time of the SNSPD detection pulse synchronously triggered by the interpolated synchronous calibration signal as the start signal is ΔT0+ΔT'. ΔT' is caused by the additional jitter of pulse accumulation. At the same time, the recovery time of each SNSPD detection pulse timestamp read out by the multi-channel TDC module relative to its previous timestamp is calculated as the recovery time T of this detection. rec ;

[0014] S04: Increase T rec The step size is , and the histograms of the arrival time ΔT0+ΔT' are generated for the detection pulse timestamps in multiple recovery time intervals. The Gaussian fitting is performed on the timestamp distribution in each histogram to obtain the distribution mean μ and half-maximum full width of its arrival time. (μ0-μ) is used as the ordinate, μ0 is the stable value of μ, T rec As the abscissa, a calibration curve is obtained.

[0015] In the preferred technical solution, when the histogram is generated in step S04, T rec The timestamps ≤6.4ns are merged to generate a sub-histogram. rec All timestamps ≥100ns are merged to generate a sub-histogram.

[0016] In a preferred technical solution, the correction curve is calibrated according to the trigger threshold with the maximum average rising edge voltage slew rate when the count rate is at least tens of megacps / channel.

[0017] In the preferred technical solution, after obtaining the correction curve, it also includes dynamically and real-timely compensating the detection pulse time stamps collected under different light intensities based on the first-order time walk correction parameters in the lookup table.

[0018] In the preferred technical solution, the compensation method includes, for a photon timestamp collected by the multi-channel TDC module, finding the corresponding compensation time on the vertical axis according to its recovery time and the correction curve of the detector channel, and then adding it to the multi-channel TDC module timestamp as the compensated timestamp.

[0019] The present invention further discloses a jitter calibration system for a superconducting nanowire single-photon detector, which is applied to the jitter calibration device mentioned above. The jitter calibration system comprises:

[0020] The timestamp acquisition module uses the pulse signal with a pulse width of 1.5ns and a period of 51.2ns sent by the GT transceiver on the FPGA platform as the synchronous calibration signal of the laser pulse to acquire the timestamp with a trigger threshold of 460mV on the multi-channel TDC module;

[0021] The synchronous calibration signal interpolation module interpolates 63 data points equidistantly between adjacent timestamps of the synchronous calibration signal as a 1.25 GHz synchronous calibration signal with the same frequency as the laser pulse;

[0022] In the calculation module, there is only a fixed delay ΔT0 between the interpolated synchronous calibration signal and the periodic photon pulse signal. The arrival time of the SNSPD detection pulse synchronously triggered by the interpolated synchronous calibration signal as the start signal is ΔT0+ΔT', where ΔT' is caused by the additional jitter of pulse accumulation. At the same time, the recovery time of each SNSPD detection pulse timestamp read out by the multi-channel TDC module relative to its previous timestamp is calculated as the recovery time T of this detection. rec ;

[0023] Calibration curve generation module, add T rec The step size is , and the histograms of the arrival time ΔT0+ΔT' are generated for the detection pulse timestamps in multiple recovery time intervals. The Gaussian fitting is performed on the timestamp distribution in each histogram to obtain the distribution mean μ and half-maximum full width of its arrival time. (μ0-μ) is used as the ordinate, μ0 is the stable value of μ, T rec As the abscissa, a calibration curve is obtained.

[0024] Compared with the prior art, the present invention has the following significant advantages:

[0025] 1. No need to add additional CFD before TDC in the SNSPD detection signal readout part, but only a simple single threshold comparator is needed, which significantly saves hardware cost and facilitates the expansion of multi-channel SNSPD.

[0026] 2. For a determined TDC comparator threshold, the calibrated jitter correction curve only requires the time interval between two adjacent photon detections of the same SNSPD as input. This low-complexity correction algorithm is easy to implement on hardware platforms such as FPGAs through lookup tables and has good real-time potential.

[0027] 3. For the same SNSPD and determined comparator threshold, the calibration curve calibrated at a certain counting rate is also applicable to working scenarios with other photon counting rates, which can ensure the robustness of the jitter optimization method under different signal photon intensities. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the additional time jitter of a single threshold-triggered photon of the TDC caused by pulse pileup at high count rates of the SNSPD;

[0029] Figure 2 Principle block diagram of the jitter calibration device of the superconducting nanowire single-photon detector of this embodiment;

[0030] Figure 3 Schematic diagram of original waveforms of two signals used for additional jitter calibration on the FPGA of this embodiment;

[0031] Figure 4 To interpolate 63 points from the 19.53125MHz periodic signal as a 1.25GHz SYNC signal;

[0032] Figure 5 SYNC and periodic laser pulses used for calibration after interpolation;

[0033] Figure 6 The generated histogram and Gaussian fitting diagram are shown below;

[0034] Figure 7 The additional jitter correction curve for each pixel at 50mV TDC trigger threshold and 25Mcps count per unit;

[0035] Figure 8 Comparison of the timestamp distribution of the photon response triggered by the 1.25 GHz SYNC signal before and after compensation of the additional jitter for a single SNSPD at a count rate of about 25 Mcps. DETAILED DESCRIPTION

[0036] The principle of the present invention is to provide a calibration curve for the relationship between the additional jitter of SNSPD detection photons caused by pulse accumulation and the detection recovery time, and compensate for the additional jitter, which can solve the jitter deterioration problem of SNSPD at high counting rates in high-speed detection applications.

[0037] Glossary:

[0038] 1. SNSPD (Superconducting Nanowire Single Photon Detector), superconducting nanowire single photon detector;

[0039] 2. TDC (Time-digital Converter), time-digital converter;

[0040] 3. FPGA (Field Programmable Gate Array), field programmable gate array;

[0041] 4. GT (Gigabyte Transceiver), gigabit transceiver;

[0042] 5. FWHM (Full Width at Half Maxima), full width at half height;

[0043] 6. cps (Counts per second), count rate per second;

[0044] 7. CFD (Constant Fraction Discriminator), constant fraction discriminator.

[0045] Embodiment 1:

[0046] like Figure 2 As shown, a jitter calibration device for a superconducting nanowire single-photon detector includes an FPGA platform for generating a periodic pulse calibration signal, a radio frequency pulse amplifier, a lithium niobate electro-optic modulator and its bias voltage controller, a 1550nm 3kHz linewidth distributed feedback laser, a programmable optical attenuation, a three-paddle polarization controller, an SNSPD single-photon detector, a multi-channel TDC module, and a host computer for processing data.

[0047] First, at the transmitting end, the two GT transceivers on the FPGA platform are encoded separately to generate a narrow pulse signal with a repetition rate of 1.25GHz and a pulse width of 200ps and another synchronous calibration signal (SYNC) with a repetition rate of 19.53125MHz and a pulse width of 1.5ns. The first signal is used to pass through the RF pulse amplifier, the lithium niobate electro-optic modulator and its bias voltage controller and the 1550nm The 3kHz linewidth distributed feedback laser performs electro-optical conversion to generate a high-modulation extinction ratio narrow pulse laser signal with the same repetition rate and pulse width, which is connected to the 16-pixel SNSPD system after appropriate optical attenuation and bias controller to trigger the detector's response to periodic photon-level signals. The detection pulse signal of the order of hundreds of mV generated by the detector's matching readout electronics system is received by the 16 channels of the multi-channel TDC module triggered by a single comparator threshold and the timestamp is read out; at the same time, the SYNC signal period generated by another GT transceiver is 64 times that of the previous signal, which is directly connected to the multi-channel TDC module and the timestamp is read out by an additional channel. The host computer processes the timestamps received by the multi-channel TDC module and generates a correction curve for additional jitter according to the method described below.

[0048] Among them, the RF pulse amplifier, lithium niobate electro-optic modulator and its bias voltage controller and 1550nm line width distributed feedback laser as the photoelectric conversion unit is a preferred embodiment, and of course it can also be a photoelectric conversion unit of other structures, which is not limited here. The RF pulse amplifier of the photoelectric conversion unit is connected to a GT transceiver of the FPGA platform, and the RF pulse amplifier is also connected to the lithium niobate electro-optic modulator, and the lithium niobate electro-optic modulator is connected to the 1550nm line width distributed feedback laser and the modulator bias voltage controller.

[0049] The SNSPD system includes a 16-pixel niobium nitride SNSPD array and its supporting readout electronics and cryogenic refrigeration system.

[0050] The readout electronics include a DC bias system, which is connected to a 16-pixel niobium nitride SNSPD array and a low-noise RF amplifier through a bias tee. The 16-pixel niobium nitride SNSPD array is connected to a quasi-constant voltage bias circuit, and the 16-pixel niobium nitride SNSPD array is connected to a low-noise RF amplifier after passing through a 2.4K cryogenic refrigeration and vacuum system.

[0051] Preferably, the number of programmable optical attenuations is two.

[0052] Figure 3-5 The original simulation waveforms of the two signals used in the calibration process of the correction curve in the FPGA are given, as well as the waveforms of the SYNC electric pulse and the optical pulse that triggers the SNSPD collected by a high-bandwidth oscilloscope.

[0053] The degree of obvious jitter deterioration of SNSPD at high count rates (generally tens of megacps (Mcps)) is closely related to the recovery time of the detector pixel (the time interval between two adjacent photon detections), especially in the range of several nanoseconds to tens of nanoseconds. The additional jitter will vary dramatically with the size of the recovery time. Therefore, the purpose of selecting an extremely short period of laser pulse to trigger the SNSPD is to make the subsequent calibrated recovery time step small enough (0.8ns) to more accurately characterize the correction curve, that is, adjacent detection events must be responses to two laser pulses before and after with an interval of an integer multiple of 800ps, except for noise counts. At the same time, we use another TXP2 of the GT transceiver on the transmitting end FPGA to send a pulse signal with a pulse width of 1.5ns and a period of 51.2ns as the SYNC signal of the laser pulse. The timestamp is collected on the multi-channel TDC module with a trigger threshold of 460mV to adapt to the minimum signal pulse width input of 350ps and the readout dead time requirement of 1.5ns of the time-to-digital converter TDC. Then, 63 data points are equidistantly interpolated between adjacent timestamps of the SYNC signal as a 1.25GHz SYNC signal with the same frequency as the laser pulse, as shown in Figure 1. Figure 4 If we do not consider the influence of the photon arrival time distribution within the 200ps broadening range of the laser pulse, we can assume that there is only a fixed delay ΔT0 between the interpolated SYNC signal and the periodic photon pulse signal, as shown in Figure 5 As shown in FIG. 1 , the arrival time of the SNSPD detection pulse synchronously triggered by the interpolated SYNC as the start signal is ΔT0+ΔT' (ΔT' is caused by the pulse pile-up additional jitter), and the recovery time of each SNSPD detection pulse timestamp read by TDC relative to its previous timestamp is calculated (in Figure 1 The interval between the two black actual triggers in the figure is approximately taken as the recovery time T of this detection. rec The basis for this approximation is that the additional time jitter caused by pile-up is generally hundreds of picoseconds, and the change in the additional jitter compensation value caused by the recovery time change of hundreds of picoseconds on the correction curve can be ignored.

[0054] Then 800ps can be used as T rec The minimum step size of the increase, for T rec The detection pulse timestamps in each recovery time interval of ∈(6.4,7.2),(7.2,8.0),…,(99.2,100.0)ns generate histograms of arrival time ΔT0+ΔT', and Gaussian fitting is performed on the timestamp distribution in each histogram to obtain the distribution mean μ and half-maximum full width FWHM of its arrival time, as follows: Figure 6 As shown. recThe reason why the statistical interval has a lower limit is that when the recovery time is less than 6.4ns, the number of detection pulse timestamps in the 800ps recovery time subinterval is too small to effectively perform Gaussian fitting on the timestamp arrival time distribution in the subinterval. Therefore, T rec The timestamps ≤6.4ns are combined to generate a sub-histogram. The upper limit exists because the pulse accumulation jitter effect corresponding to the recovery time above 100ns basically disappears, so the T rec All timestamps ≥100ns are also merged to generate a sub-histogram.

[0055] from Figure 6 It can be seen that as T rec As the pulse accumulation effect disappears, the mean μ of the Gaussian fitting also moves to the right and tends to a stable value μ0. rec The offset of the mean μ corresponding to the sub-histogram under the condition of μ0 can be considered as the deterministic part of the additional jitter that can be compensated; while the FWHM (full width at half maximum) of the fitting is smaller at T rec This is because the short detection pulse interval leads to insufficient nanowire current, which causes the pulse amplitude to decrease (e.g. Figure 1 The second SNSPD detection pulse in the figure shows that the voltage slew rate at the TDC threshold trigger is reduced, which will introduce more serious jitter under the same voltage noise. This part is the non-deterministic part of the additional jitter that cannot be compensated. After obtaining μ0, the different T rec The mean μ minus μ0 obtained after Gaussian fitting of the sub-histogram under is used as the ordinate, T rec (Here the step length is 800 ps) as the horizontal axis to obtain the calibration curve.

[0056] According to the above method, Figure 7 The (μ0-μ) of all pixels in the SNSPD array with respect to T is given in the working scenario of a single-channel count rate of about 25Mcps. rec As an example, the additional jitter correction curve of 20ns is mainly limited by the combined effect of the accumulation of the falling edge of the pulse and the reduction of the amplitude caused by the incomplete recovery of the nanowire current. The detection pulse time jitter distribution at high count rate mainly shows an asymmetric forward tail; while the additional jitter around 22ns is due to the combined effect of the negative overshoot of the falling edge and the reduction of the amplitude caused by the incomplete recovery of the nanowire current, which is the main cause of the backward tail. rec Continue to increase it until it exceeds the time interval of the crosstalk between the front and rear detection pulses, and the influence of the additional jitter completely disappears.

[0057] The calibration of the correction curve is theoretically only related to the SNSPD parameters and the inherent characteristics of the readout circuit, as well as the pulse edge trigger threshold used by the TDC. The calibration curve calibrated at a certain count rate is suitable for additional jitter compensation in different photon count rate scenarios. However, it is best to calibrate the correction curve at the trigger threshold with the maximum average rising edge voltage slew rate near the count rate level in the actual detector working scenario, and this count rate should be at least tens of Mcps / channel, so that Figure 6 Smaller T rec The number of samples of the corresponding sub-histogram increases, so that it also contains enough samples for Gaussian fitting and generates an accurate estimate of the mean μ. For high-speed real-time applications, it is only necessary to calculate the difference between adjacent timestamps on the same channel (the recovery time experienced by the detector of the channel before the detection), and then the detection pulse timestamps collected under different light intensities can be dynamically compensated in real time by the first-order time walk correction parameters based on the lookup table under the condition of fixed trigger threshold and detector parameters (that is, for a photon timestamp collected by the multi-channel TDC module, the corresponding compensation time on the vertical axis is found according to its recovery time and the correction curve of the detector channel, and then added to the timestamp of the multi-channel TDC module as the compensated timestamp, and the lookup table structure can be used), so it has great engineering application value.

[0058] Figure 8 The time domain distribution histogram of SNSPD detected photons before and after applying jitter compensation at a higher count rate of 25Mcps in a single channel is given (shown in red and blue respectively, and the photon timestamp count in the inset is the logarithmic axis).

[0059] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A jitter calibration device for a superconducting nanowire single-photon detector, characterized in that: The invention comprises an FPGA platform, wherein the FPGA platform is used to generate a periodic pulse calibration signal. The two GT transceivers on the FPGA platform are respectively encoded to generate a first narrow pulse signal and another synchronous calibration signal. The first narrow pulse signal is subjected to electro-optical conversion by a photoelectric conversion unit to generate a high-modulation extinction ratio narrow pulse laser signal with the same repetition rate and pulse width, which is connected to an SNSPD system after passing through an optical attenuation and bias controller to trigger the detector's response to a periodic photon-level signal. The detection pulse signal generated by a low-noise radio frequency amplifier is received via multiple channels of a multi-channel TDC module and a timestamp is read out. Meanwhile, the other synchronous calibration signal has a period of 64 times that of the first narrow pulse signal, is directly connected to the multi-channel TDC module, and a timestamp is read out by an additional channel. The host computer processes the timestamps of each channel received by the multi-channel TDC module and generates a correction curve for additional jitter.

2. The jitter calibration device for superconducting nanowire single-photon detector according to claim 1, characterized in that: The photoelectric conversion unit includes a radio frequency pulse amplifier, a lithium niobate electro-optical modulator and its bias voltage controller and a 1550nm line width distributed feedback laser. The radio frequency pulse amplifier is connected to a GT transceiver of the FPGA platform. The radio frequency pulse amplifier is also connected to the lithium niobate electro-optical modulator. The lithium niobate electro-optical modulator is connected to the 1550nm line width distributed feedback laser and the modulator bias voltage controller.

3. The jitter calibration device for superconducting nanowire single-photon detector according to claim 1, characterized in that: The first narrow pulse signal is a narrow pulse signal with a repetition rate of 1.25 GHz and a pulse width of 200 ps, ​​and the other synchronous calibration signal is a synchronous calibration signal with a repetition rate of 9.53125 MHz and a pulse width of 1.5 ns.

4. A jitter calibration method for a superconducting nanowire single-photon detector, characterized in that: Applied to the jitter calibration device according to any one of claims 1 to 3, the jitter calibration method comprises the following steps: S01: Use the pulse signal with a pulse width of 1.5ns and a period of 51.2ns sent by the GT transceiver on the FPGA platform as the synchronous calibration signal of the laser pulse to collect the timestamp with a trigger threshold of 460mV on the multi-channel TDC module; S02: equidistantly interpolate 63 data points between adjacent timestamps of the synchronous calibration signal as a 1.25 GHz synchronous calibration signal with the same frequency as the laser pulse; S03: There is only a fixed delay ΔT0 between the interpolated synchronous calibration signal and the periodic photon pulse signal. The arrival time of the SNSPD detection pulse synchronously triggered by the interpolated synchronous calibration signal as the start signal is ΔT0+ΔT'. ΔT' is caused by the additional jitter of pulse accumulation. At the same time, the recovery time of each SNSPD detection pulse timestamp read out by the multi-channel TDC module relative to its previous timestamp is calculated as the recovery time T of this detection. rec ; S04: Increase T rec The step size is , and the histograms of the arrival time ΔT0+ΔT' are generated for the detection pulse timestamps in multiple recovery time intervals. The Gaussian fitting is performed on the timestamp distribution in each histogram to obtain the distribution mean μ and half-maximum full width of its arrival time. (μ0-μ) is used as the ordinate, μ0 is the stable value of μ, T rec As the abscissa, a calibration curve is obtained.

5. The jitter calibration method of the superconducting nanowire single-photon detector according to claim 4, characterized in that: When the histogram is generated in step S04, T rec The timestamps ≤6.4ns are merged to generate a sub-histogram. rec All timestamps ≥100ns are merged to generate a sub-histogram.

6. The jitter calibration method of the superconducting nanowire single-photon detector according to claim 4, characterized in that: When the count rate is at least tens of megacps / channel, the correction curve is calibrated according to the trigger threshold with the maximum average rising edge voltage slew rate.

7. The jitter calibration method of the superconducting nanowire single-photon detector according to claim 4, characterized in that: After the correction curve is obtained, the method also includes dynamically and real-timely compensating the detection pulse time stamps collected under different light intensities based on the first-order time walk correction parameters of the lookup table.

8. The jitter calibration method of the superconducting nanowire single-photon detector according to claim 7, characterized in that: The compensation method includes, for a photon timestamp collected by a multi-channel TDC module, finding the corresponding compensation time on the vertical axis according to its recovery time and the calibration curve of the detector channel, and then adding it to the multi-channel TDC module timestamp as the compensated timestamp.

9. A jitter calibration system for a superconducting nanowire single-photon detector, characterized in that: Applicable to the jitter calibration device according to any one of claims 1 to 3, the jitter calibration system comprises: The timestamp acquisition module uses the pulse signal with a pulse width of 1.5ns and a period of 51.2ns sent by the GT transceiver on the FPGA platform as the synchronous calibration signal of the laser pulse to acquire the timestamp with a trigger threshold of 460mV on the multi-channel TDC module; The synchronous calibration signal interpolation module interpolates 63 data points equidistantly between adjacent timestamps of the synchronous calibration signal as a 1.25 GHz synchronous calibration signal with the same frequency as the laser pulse; In the calculation module, there is only a fixed delay ΔT0 between the interpolated synchronous calibration signal and the periodic photon pulse signal. The arrival time of the SNSPD detection pulse synchronously triggered by the interpolated synchronous calibration signal as the start signal is ΔT0+ΔT', where ΔT' is caused by the additional jitter of pulse accumulation. At the same time, the recovery time of each SNSPD detection pulse timestamp read out by the multi-channel TDC module relative to its previous timestamp is calculated as the recovery time T of this detection. rec ; Calibration curve generation module, add T rec The step size is , and the histograms of the arrival time ΔT0+ΔT' are generated for the detection pulse timestamps in multiple recovery time intervals. The Gaussian fitting is performed on the timestamp distribution in each histogram to obtain the distribution mean μ and half-maximum full width of its arrival time. (μ0-μ) is used as the ordinate, μ0 is the stable value of μ, T rec As the abscissa, a calibration curve is obtained.

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