CN111220286A

CN111220286A - Single photon detector parameter measuring system and method

Info

Publication number: CN111220286A
Application number: CN202010110979.3A
Authority: CN
Inventors: 任瑞; 祝月兵; 叶鹏; 张洪波; 冯波; 刘江; 杨林; 刘志辉
Original assignee: Sichuan Jiuzhou Electric Group Co Ltd
Current assignee: Sichuan Jiuzhou Electric Group Co Ltd
Priority date: 2020-02-24
Filing date: 2020-02-24
Publication date: 2020-06-02
Anticipated expiration: 2040-02-24
Also published as: CN111220286B

Abstract

The invention relates to a single photon detector parameter measuring system and a method, wherein the system comprises a light source module, a data acquisition processing module and a display control module; the system also comprises a signal source and a time delay submodule, wherein the signal source and the time delay submodule are used for receiving the control signal output by the data acquisition and processing module, outputting a time sequence generation signal to the light source module according to the control signal to control the light source module to generate the single photon pulse signal time, outputting a gate control signal to the single photon detector to be detected at the same time, and controlling the door opening time of the single photon detector to be detected, so that the time of the single photon pulse signal reaching the single photon detector to be detected is consistent with the door opening time of the. The system makes up the problem of low parameter precision of the single photon detector caused by low synchronism of the measurement system, and improves the measurement precision.

Description

Single photon detector parameter measuring system and method

Technical Field

The invention relates to the field of single photon detection, in particular to a single photon detector parameter measuring system and method.

Background

With the continuous breakthrough of quantum technology in theory and experiment, leading-edge technologies such as quantum communication and quantum detection are receiving more and more attention, and single photon detectors with photon-level sensitivity are used as important parts of quantum communication and quantum detection, and are used more and more widely. For a single-photon detector, the detection efficiency, the dead time, the post-pulse probability and the like of the single-photon detector are taken as important parameters to greatly influence the use of the single-photon detector, and meanwhile, the important parameters such as the detection efficiency, the dead time, the post-pulse probability and the like of the single-photon detector are measured and explained when the single-photon detector leaves a factory; however, as the single photon detector is used, the performance parameters of the single photon detector can drift, and new measurement and calibration are needed.

At present, the measurement of parameters of a single photon detector is not high in precision due to the problem of low system synchronism, meanwhile, a monitorable stable single photon source is not available, the measurement effect of the parameters of the single photon detector is influenced, and furthermore, the traditional parameter measurement of the single photon detector is generally based on a set of experimental equipment built under laboratory conditions, and mature instrument equipment is not available, so that the measurement is inconvenient and not suitable for market requirements.

Disclosure of Invention

The invention provides a single photon detector parameter measuring system, which solves the problem of low precision of measuring single photon detector parameters due to low synchronism of the measuring system.

The invention is realized by the following technical scheme:

the invention provides a single photon detector parameter measuring system, which comprises a light source module, a data acquisition and processing module and a display control module:

the light source module is used for generating a single photon pulse signal and outputting the single photon pulse signal to the single photon detector to be detected;

the data acquisition processing module receives a counting signal generated by counting the single photon pulse signal by the single photon detector to be detected, and analyzes and calculates the counting signal to obtain the parameter of the single photon detector to be detected;

the display control module is connected with the data acquisition and processing module and is used for human-computer interaction;

the system also comprises a signal source and a delay submodule;

the signal source and delay submodule is used for receiving a control signal output by the data acquisition and processing module, outputting a time sequence generation signal to the light source module according to the control signal to control the light source module to generate single photon pulse signal time, and simultaneously outputting a gate control signal to the single photon detector to be detected to control the door opening time of the single photon detector to be detected, so that the time of the single photon pulse signal reaching the single photon detector to be detected is consistent with the door opening time of the single photon detector to be detected;

in the technical scheme, a command is sent to a data acquisition and processing module through a display control module to control the data acquisition and processing module to start parameter measurement of the single photon detector to be detected, a signal source and a delay submodule receive a control signal output by the data acquisition and processing module, generate a time sequence generation signal and output the time sequence generation signal to a light source module, and simultaneously generate a gate control signal and output the gate control signal to the single photon detector to be detected; triggering the light source module to generate a single photon pulse signal through the time sequence generation signal and outputting the single photon pulse signal to the single photon detector to be detected; the gate control signal is precisely delayed and then output to the single photon detector to be detected, so that the single photon detector to be detected can be controlled according to the delayed gate control signal; because the detection time of the single photon detector to be detected is short, extremely high requirements are put forward on the time sequence control precision and the signal synchronism of the system; the signal source and the delay submodule are realized by adopting a special time sequence chip and a special delay chip, can provide a multi-path precise clock signal with good synchronism for the system, and realize the precise delay adjustability of several picoseconds between the signals, thereby ensuring that the system can realize precise time sequence alignment and improving the parameter measurement precision of the single photon detector to be measured; the gate opening time of the single photon detector to be detected is accurately controlled through the gate control signal, and is matched with the time of the single photon pulse signal reaching the single photon detector to be detected, so that the synchronism of the system is ensured, and the measurement precision of the parameters of the single photon detector to be detected is improved; when the single photon detector to be detected receives the single photon pulse signal, counting the single photon pulse signal, and outputting the counting signal to the data acquisition and processing module, wherein the data acquisition and processing module obtains parameters of the single photon detector to be detected through analysis and processing according to the counting signal; according to the technical scheme, the single photon detector parameter measuring system can realize a man-machine interaction function, and the time sequence control precision and the signal synchronism of the system are ensured through the signal source and the delay submodule, so that the measuring precision of the parameters of the single photon detector to be measured is improved.

As a further improvement of the invention, the data acquisition and processing module comprises a control and data processing module and a time-amplitude conversion measuring module;

the control and data processing module is connected with the signal source, the delay submodule and the display control module, and is used for outputting control information to the signal source and the delay submodule, receiving a user instruction from the display control module and outputting parameters of the single photon detector to be detected from the display control module;

the signal source and delay submodule is also used for outputting a starting signal to the time-amplitude conversion measuring module according to the control signal output by the control and data processing module, and controlling the time-amplitude conversion measuring module to start timing;

the time-amplitude conversion measuring module is used for receiving a starting signal output by the signal source and the delay submodule and a counting signal output by the single photon detector to be detected, stopping timing after receiving the counting signal output by the single photon detector to be detected, calculating timing duration according to the starting timing time and the stopping timing time, and outputting the timing duration signal to the control and data processing module;

the control and data processing module is used for receiving the timing duration signal output by the amplitude conversion measuring module and analyzing and calculating parameters of the single photon detector to be detected according to the timing duration signal;

in the technical scheme, after a signal source and a delay submodule receive a control signal output by a control and data processing module, a time sequence generation signal and a gate control signal are generated, a starting signal is also generated at the same time, the starting signal is output to a time-amplitude conversion measuring module after precision delay processing is carried out, and timing is started after the time-amplitude conversion measuring module receives the starting signal; after the amplitude conversion measurement module receives a counting signal sent by the single photon detector to be detected, the counting signal is used as a stop signal, timing is suspended, timing duration of timing starting time and timing stopping time is calculated, the timing duration signal is output to the control and data processing module, and the control and data processing module analyzes and calculates parameters of the single photon detector to be detected according to the timing duration signal; the counting signals are pulse signals, and the number of the counting pulse signals needs to be obtained for calculating the parameters of the single photon detector to be detected, so that the number of the counting pulse signals is recorded by the amplitude conversion measuring module when the counting pulse signals are received, and the number of the counting pulse signals and the timing duration are simultaneously output to the control and data processing module for analysis and calculation, thereby obtaining the parameters of the single photon detector to be detected.

Further, the light source module comprises a light pulse signal generator, an attenuation module, a first beam splitting module and a monitoring module;

the optical pulse signal generator is used for receiving the time sequence generation information output by the signal source and the delay submodule, generating an optical pulse signal and outputting the optical pulse signal to the attenuation module;

the attenuation module is used for receiving the optical pulse signal output by the optical pulse signal generator, attenuating the optical pulse signal and outputting the optical pulse signal to the first beam splitting module;

the first beam splitting module is used for receiving the optical pulse signals output by the attenuation module, dividing the optical pulse signals into two paths, outputting one path of optical pulse signals to the monitoring module, and outputting the other path of optical pulse signals serving as single photon pulse signals to the single photon detector to be detected;

the monitoring module is used for receiving one path of optical pulse signals output by the first beam splitting module, performing coincidence counting on the optical pulse signals to obtain a coincidence counting result, and mapping the coincidence counting result and the average photon number of the single optical pulse signals by utilizing a mapping relation between a pre-calibrated coincidence counting result and the average photon number of the single optical pulse signals to obtain the average photon number information of the single optical pulse signals and outputting the average photon number information of the single optical pulse signals to the control and data processing module;

in the technical scheme, an optical pulse signal generator outputs an initial optical signal after receiving a time sequence generation signal by adopting a picosecond pulse laser, attenuates the initial optical pulse signal through an attenuation module, attenuates the energy of the optical pulse signal to a single photon magnitude order to meet the requirement of single photon preparation, and then outputs the optical pulse signal subjected to attenuation processing to a first beam splitting module, wherein the first beam splitting module is a first beam splitter and is used for splitting the input photonic pulse signal into two paths according to equal proportion, one path of optical pulse signal is output to a monitoring module, and the monitoring module is an HBT experimental system; taking the other path of optical pulse signal as the output end of the single photon source, and outputting the single photon pulse signal to the single photon detector to be detected; after receiving the optical pulse signals output by the first beam splitting module, the monitoring module performs coincidence counting operation on the optical pulse signals, and mapping the coincidence counting result and the average photon number of the optical pulse signals by using a mapping relation of a pre-calibrated coincidence counting result and the average photon number of the optical pulse signals to obtain the average photon number information of the single photon pulse signals; because the first beam splitter divides the optical pulse signals into two paths according to equal proportion, and the two paths of optical pulse signals are equivalent to each other, the state of the single photon source preparation system output state can be represented by the other path of single photon pulse signals for output according to the result output by the monitoring module, and the real-time monitoring of the single photon source preparation system output state is completed, wherein the coincidence counting operation is the prior art, and is not repeated in the specification; by the technical scheme, the number of single photons generated by a single photon source is monitored in real time, and the accuracy of the number of the single photons generated by the system is ensured.

Further, the monitoring module comprises a fourth beam splitting module, a first single-photon detector, a second single-photon detector and a data processing unit;

the fourth beam splitting module is used for receiving the optical pulse signals output by the first beam splitting module, dividing the optical pulse signals into two paths, outputting one path of optical pulse signals to the first single-photon detector, and outputting the other path of optical pulse signals to the second single-photon detector;

the first single-photon detector and the second single-photon detector are used for receiving the optical pulse signals output by the fourth beam splitting module, carrying out photon counting detection on the photon number in each received optical pulse signal and outputting the counting result to the data processing unit;

the data processing unit is used for receiving a first photon counting result output by the first single photon detector and a second photon counting result output by the second single photon detector, performing coincidence counting on the first photon counting result and the second photon counting result to obtain a coincidence counting result, mapping to obtain average photon number information of the single photon pulse signal by using a mapping relation between a preset coincidence counting result and the average photon number of the photon pulse signal, and outputting the average photon number information to the control and data processing module;

in the technical scheme, the fourth beam splitting module is a fourth beam splitter; after receiving the optical pulse signal output by the first beam splitter, the fourth beam splitter further divides the optical pulse signal into two paths according to the equal proportion, outputs one path of optical pulse signal to the first single-photon detector, outputs the other path of optical pulse signal to the second single-photon detector, counts and detects the photon number in the optical pulse signal through the first single-photon detector and the second single-photon detector, outputs a photon counting result to the data processing unit, performs coincidence counting operation on the counting results of the two single-photon detectors by the data processing unit, and maps and obtains the average photon number information of the single-photon pulse signal and outputs the average photon number information of the single-photon signal to the control and data processing module by using the mapping relation between the coincidence counting result and the average photon number of the single-photon pulse signal, which is calibrated in advance, by using the nondetachability of photons; by adopting the structure of the monitoring module in the technical scheme, the average photon number in the output single photon pulse signal can be accurately monitored on the photon magnitude, so that the real-time monitoring of the state of the single photon source output single photon pulse signal is completed.

Further, the light source module further comprises a polarization module; the polarization module comprises a light path selection module, a second beam splitting module, a polarization control module and a polarization measurement module;

the optical path selection module is used for receiving the optical pulse signal output by the optical pulse signal generator and selectively outputting the optical pulse signal to the polarization control module or selectively outputting the optical pulse signal to the attenuation module;

the polarization control module is used for receiving the optical pulse signal output by the optical path selection module, controlling the optical pulse signal to reach a specific polarization state, and outputting the optical pulse signal with the specific polarization state to the second beam splitting module;

the second beam splitting module is used for receiving the optical pulse signal output by the polarization control module, dividing the optical pulse signal into two paths, outputting one path of optical pulse signal to the polarization measurement module, and outputting the other path of optical pulse signal to the attenuation module;

the polarization measurement module receives the optical pulse signal output by the second beam splitting module, measures the optical pulse signal to obtain polarization state information of the optical pulse signal, and outputs the polarization state measurement information to the monitoring module;

in the technical scheme, the optical path selection module is an optical switch, the optical switch receives an initial optical pulse signal output by a picosecond pulse laser, and the optical pulse signal is selectively output to the polarization control module or directly output to the attenuation module, so that the whole system can selectively generate a single-photon pulse signal with a polarization state or a single-photon pulse signal without the polarization state to meet the actual diversified output requirements; when the polarization control module receives the optical pulse signal output by the optical switch and controls the optical pulse signal to reach any required polarization state, the optical pulse signal with the polarization state is output to a second beam splitting module, the second beam splitting module is a second beam splitter, the second beam splitter divides the optical pulse signal into two paths according to the proportion of 10:90, 10% of the optical pulse signal is output to the polarization measurement module, and 90% of the optical pulse signal is output to the attenuation module; the polarization measurement module receives the optical pulse signal output by the second beam splitter, measures the polarization state of the optical pulse signal, and outputs the polarization state measurement information to the data processing unit in the monitoring module, the data processing unit judges whether the angle of the polarization state in the optical pulse signal is too large or too small according to the polarization state measurement information, if the angle of the polarization state in the optical pulse signal is too large, the polarization control module is subjected to polarization feedback control to reduce the angle of the polarization state, if the angle of the polarization state is too small, the polarization control module is subjected to polarization feedback control to increase the angle of the polarization state, and therefore the polarization state in the optical pulse signal is adjusted, and the control of the polarization state is more accurate and stable.

Further, the attenuation module comprises a variable attenuation module, a third beam splitting module, a light energy measuring module and a fixed attenuation module;

the variable attenuation module is used for receiving the optical pulse signal output by the optical path selection module and receiving the other optical pulse signal output by the second beam splitting module, performing variable attenuation processing on the optical pulse signal, and outputting the processed optical pulse signal to the third beam splitting module;

the third beam splitting module is used for receiving the optical pulse signals processed by the variable attenuation module, dividing the optical pulse signals into two paths, outputting one path of optical pulse signals to the optical energy measuring module, and outputting the other path of optical pulse signals to the fixed attenuation module;

the optical energy measuring module is used for receiving one path of optical pulse signals output by the third beam splitting module, measuring the optical energy value of the optical pulse signals and outputting the optical energy value measuring result to the monitoring module;

the fixed attenuation module is used for receiving the other path of optical pulse signal output by the third beam splitting module, performing fixed attenuation processing on the optical pulse signal and outputting the processed optical pulse signal to the first beam splitting module;

in the technical scheme, after the optical pulse signal enters the variable attenuation module through the second beam splitter or enters the variable attenuation module through the optical switch, the variable attenuation module performs variable attenuation on the energy of the optical pulse signal, so that the flexible control on the energy of the output optical pulse signal is realized; after the optical pulse signal enters a third beam splitting module through the variable attenuation module, the third beam splitting module is a third beam splitter, the third beam splitter divides the optical pulse signal into two paths according to the proportion of 99:1, 99% of the optical pulse signal is output to the optical energy measuring module, and 1% of the optical pulse signal is output to the fixed attenuation module; after the optical energy measuring module receives the optical pulse signal output by the third beam splitter, measuring the energy in the optical pulse signal, and outputting the optical energy value measuring result in the optical pulse signal to a data processing unit in the monitoring module; when the fixed attenuation module receives the optical pulse signal output by the third beam splitter, the fixed attenuation module accurately attenuates the optical pulse signal, so that the energy of the attenuated optical pulse signal reaches the single photon magnitude and is output to the first beam splitter; according to the technical scheme, after attenuation processing of the optical pulse signal is completed, the single photon magnitude optical pulse signal is obtained, photon energy is measured in proportion through the optical energy measuring module, the optical energy value measuring result is input into the data processing unit of the monitoring module, and the data processing unit performs feedback control on the variable attenuation module.

The monitoring module is further used for receiving polarization state measurement information output by the polarization measurement module and an optical energy value measurement result output by the optical energy measurement module, performing feedback control on the polarization control module according to the polarization state measurement information, and performing feedback control on the variable attenuation module according to the coincidence counting result and the optical energy value measurement result;

in the technical scheme, a data processing unit in a monitoring module judges whether the angle of the polarization state in the optical pulse signal is too large or too small according to the measurement information of the polarization state, if so, the polarization control module is subjected to polarization feedback control to adjust the polarization state angle to be small, if the polarization state angle is too small, the polarization control module is subjected to polarization feedback control to adjust the polarization state angle to be large, thereby adjusting the angle of the polarization state in the optical pulse signal, ensuring the control of the polarization state to be more accurate and stable, and the data processing unit in the monitoring module calculates the output energy of the optical pulse signal according to a certain proportion according to the measurement result of the optical energy value, and simultaneously combines the coincidence counting result of the optical pulse signal input into the monitoring module, and performing energy feedback control on the variable attenuation module, adjusting the multiple of energy attenuation of the optical pulse signal, and ensuring the stability of single photon pulse signal output.

Further, a single photon detector parameter measuring method is provided, the single photon detector parameter measuring system is adopted for measurement, and the method comprises the following steps:

s1: the display control module outputs a starting signal to the control and data processing module to start to measure the parameters of the single photon detector to be measured;

s2: the control and data processing module receives the starting signal and outputs a control signal to the signal source and the delay submodule, and the control signal source and the delay submodule generate a time sequence generation signal, a gate control signal and a starting signal;

s3: the signal source and delay submodule outputs the time sequence generation signal to the light source module and controls the light source module to generate a single photon pulse signal; outputting the gate control signal to the single photon detector to be detected, and controlling the door opening time of the single photon detector to be detected; outputting a starting signal to the time-amplitude conversion measuring module, and controlling the time-amplitude conversion measuring module to start timing;

s4: the light source module generates a single photon pulse signal according to the time sequence generation signal, simultaneously monitors the single photon pulse signal in real time, outputs a monitoring result to the control and data processing module, and outputs the single photon pulse signal to the single photon detector to be detected;

s5: the single photon detector to be detected receives the single photon pulse signal according to the gate control signal, and simultaneously counts and detects the single photon pulse signal, generates a counting signal and outputs the counting signal to the time-amplitude conversion measuring module;

s6: the time-amplitude conversion measuring module receives a starting signal output by the signal source and the delay submodule and a counting signal output by the single photon detector to be detected, stops timing after receiving the counting signal output by the single photon detector to be detected, calculates timing duration according to the starting timing time and the stopping timing time, and outputs the timing duration signal to the control and data processing module;

s7: and when the control and data processing module receives the timing duration signal output by the time-amplitude conversion measuring module, analyzing and processing the timing duration signal to obtain the parameter of the single photon detector to be detected and sending the parameter to the display control module for displaying.

Further, step S4 includes the steps of:

s101: the optical pulse signal generator generates an optical pulse signal according to the received time sequence generation signal and outputs the optical pulse signal to the optical path selection module, and the optical pulse signal is selectively output to the polarization control module or the optical signal is selectively output to the variable attenuation module;

s102: when the optical pulse signal is selected to be output to the polarization control module, the polarization control module controls the optical pulse signal to reach a specific polarization state; the second beam splitting module is also adopted to divide the optical pulse signal with the polarization state output by the polarization control module into two paths, the polarization measurement module is adopted to measure the polarization information of one path of optical pulse signal, the polarization measurement information is output to the monitoring module, and the other path of optical pulse signal is directly transmitted to the variable attenuation module;

s103: performing variable attenuation processing on the received optical pulse signal by adopting a variable attenuation module; a third beam splitting module is adopted to divide the optical pulse signals after variable attenuation processing into two paths for output; the optical energy measuring module is used for measuring the optical energy value of one path of optical pulse signals output by the third beam splitting module, and the optical energy value measuring result is output to the monitoring module; the fixed attenuation module is adopted to perform fixed multiple attenuation processing on the other path of optical pulse signal output by the third beam splitting module and then output the optical pulse signal to the first beam splitting module;

s104: dividing the attenuated optical pulse signals into two paths by adopting a first beam splitting module, outputting one path of optical pulse signals to a monitoring module for coincidence counting, mapping to obtain single-photon-pulse-signal average photon number information according to a coincidence counting result and by utilizing a mapping relation between a pre-calibrated coincidence counting result and a single-photon-pulse-signal average photon number, outputting the single-photon-pulse-signal average photon number information to a control and data processing sub-module, and outputting the other path of optical pulse signals serving as single photon pulse signals to a single-photon detector to be detected;

s105: after the polarization measurement information is output to the monitoring module, the monitoring module performs feedback control on the polarization control module according to the polarization measurement information; and after the optical energy value measurement result is output to the monitoring module, the monitoring module performs feedback control on the variable attenuation module according to the optical energy value measurement result and the coincidence counting result.

Further, the calibration method according with the mapping relationship between the counting result and the average photon number of the single-light pulse signal, which is calibrated in advance, comprises the following steps:

s201: the number of photons contained in each single photon pulse signal approximately follows a Poisson random process, that is, when the average number of photons contained in the output single photon pulse signal is mu, the probability of outputting the single photon pulse signal containing n photons is shown as formula (1):

wherein N is 1,2,3, …, N; n is the maximum value of the number of photons contained in the photon pulse;

s202, the single-photon pulse signal is divided into two paths after passing through a beam splitter with a beam splitting ratio of S1: S2, the two paths of single-photon pulse signal light respectively enter a first single-photon detector and a second single-photon detector, and meanwhile, the response efficiency of the first single-photon detector and the response efficiency of the second single-photon detector to the single-photon pulse signal containing n photons are η respectively_1nand η_2nThe dark counting rates of the two single photon detectors are respectively R1_darkAnd R2_darkIn the case where the gating frequency is R, the probability of occurrence of dark count noise every time the door is opened is as shown in equation (2):

s203: suppose the probability of the back pulse of the first single-photon detector and the probability of the back pulse of the second single-photon detector are respectively P1_spAnd P2_spThe noise probability of the first single-photon detector and the noise probability of the second single-photon detector are respectively P1_noiseAnd P2_noiseAccording to the counting working characteristics of the single-photon detector, the following can be obtained:

wherein, mu 'and mu' are the average photon numbers of single-photon pulse signals entering the first single-photon detector and the second single-photon detector respectively;

s204: according to the coincidence counting principle, the photon counting results output by the first single-photon detector and the second single-photon detector are coincidently counted to obtain a second-order autocorrelation function output expected value of the single-photon pulse signal:

wherein N is 1,2,3, …, N is the maximum value of photon number contained in photon pulse,

the probability of coincidence with the count output 1 when the photon pulse contains n photons;

and

are respectively:

outputting an expected value g according to the second-order autocorrelation function obtained in step S204²(mu) and single photon pulse signalAnd mapping the number average photon number mu to obtain a mapping relation which accords with the counting result and the average photon number of the single photon pulse signal.

In the technical scheme, according to the principle of coincidence counting, if and only if two detectors have counting pulse signals to output, the coincidence counting outputs a value 1, and the other condition outputs 0; meanwhile, the working characteristics of the single-photon detector are analyzed, and the counting pulse output by the single-photon detector can be divided into three conditions, namely a photon counting pulse generated after responding to an input single-photon pulse signal, a back pulse caused by previous response and a dark counting pulse randomly generated by the single-photon detector; the first type is an effective pulse to be measured, and the second type and the third type are counting pulses generated due to the self characteristics of the single-photon detector, namely noise generated by the single-photon detector; using P1_noiseAnd P2_noiseThe noise generated by the two single photon detectors is measured, and meanwhile, under the condition of no external photon input, the probability of outputting counting pulses by the detectors within one-time door opening time mainly comprises dark counting noise and rear pulse noise, so that a formula (3) can be obtained; when the single photon pulse signal input into the monitoring module, namely the HBT system, only contains 0 photon, the output of the detector is only influenced by thermal noise and rear pulse, and the probability of coincidence counting output 1 is shown in a formula (5); when the single photon pulse signal input into the HBT system only contains 1 photon, the photon only enters one of the two single photon detectors, and the probability of the coincidence counting output 1 is shown in a formula (6); when the single photon pulse signal input to the HBT system contains only 2 photons, there are three cases: 2 photons all enter a first single photon detector; 1 photon enters a first single photon detector, and the other 1 photon enters a second single photon detector; 2 photons all enter a second single photon detector; therefore, the probability of coincidence with count output 1 is as shown in equation (7); from equations (5), (6) and (7), equation (8) can be derived; according to the coincidence counting principle, the photon counting results output by the first single-photon detector and the second single-photon detector are coincidently counted to obtain single-photon pulsesSecond order autocorrelation function output expectation, g, of the signal²(mu), the value is also a second-order correlation function value of the single-photon pulse signal obtained by the monitoring module through coincidence counting, therefore, through the formula (4), the relation between the average photon number mu of the single-photon pulse signal and the output expected value of the second-order autocorrelation function of the single-photon pulse signal can be obtained, the average photon number mu of the single-photon pulse signal can be correspondingly obtained through the output expected value of the second-order autocorrelation function of the single-photon pulse signal, mapping between the coincidence counting result and the average photon number of the single-photon pulse signal is realized, and the mapping relation between the coincidence counting result and the average photon number of the single-photon pulse signal is.

In conclusion, the beneficial effects of the invention are as follows:

the signal source and the delay submodule ensure the time sequence control precision and the signal synchronism of the measuring system, thereby improving the measuring precision of the parameters of the single photon detector to be measured; meanwhile, by improving the light source module, a stable single photon source can be provided for the measurement system through real-time monitoring and feedback control, so that the accuracy of parameter measurement of the single photon detector is improved, and the parameter measurement of the single photon detector can be completed more conveniently through the measurement system; the method solves the problems that the measurement system has low synchronism, so that the measurement system has low parameter precision of the single photon detector, does not have a monitorable stable single photon source, and influences the measurement effect of the single photon detector and is inconvenient to measure.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a system block diagram of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.

Example 1:

as shown in fig. 1, a single photon detector parameter measurement system includes a light source module, a data acquisition and processing module, and a display control module:

the system also comprises a signal source and a delay submodule;

the signal source and delay submodule is used for receiving the control signal output by the data acquisition and processing module, outputting a time sequence generation signal to the light source module according to the control signal to control the light source module to generate single photon pulse signal time, and simultaneously outputting a gate control signal to the single photon detector to be detected to control the door opening time of the single photon detector to be detected, so that the time of the single photon pulse signal reaching the single photon detector to be detected is consistent with the door opening time of the single photon detector to be detected.

The data acquisition and processing module comprises a control and data processing module and a time-amplitude conversion measuring module;

and the control and data processing module is used for receiving the timing duration signal output by the amplitude conversion measuring module and analyzing and calculating to obtain the parameters of the single photon detector to be detected according to the timing duration signal.

The light source module comprises a light pulse signal generator, an attenuation module, a first beam splitting module and a monitoring module;

the monitoring module is used for receiving one path of optical pulse signals output by the first beam splitting module, performing coincidence counting on the optical pulse signals to obtain a coincidence counting result, and mapping the coincidence counting result and the average photon number of the single optical pulse signals by utilizing a mapping relation of a pre-calibrated coincidence counting result and the average photon number of the single optical pulse signals to obtain the average photon number information of the single optical pulse signals and outputting the average photon number information of the single optical pulse signals to the control and data processing module.

The monitoring module comprises a fourth beam splitting module, a first single-photon detector, a second single-photon detector and a data processing unit;

the data processing unit is used for receiving a first photon counting result output by the first single photon detector and a second photon counting result output by the second single photon detector, performing coincidence counting on the first photon counting result and the second photon counting result to obtain a coincidence counting result, and mapping to obtain average photon number information of the single photon pulse signal by using a mapping relation between a preset coincidence counting result and the average photon number of the photon pulse signal and outputting the average photon number information to the control and data processing module.

The light source module further comprises a polarization module; the polarization module comprises a light path selection module, a second beam splitting module, a polarization control module and a polarization measurement module;

the polarization measurement module receives the optical pulse signal output by the second beam splitting module, measures the optical pulse signal to obtain polarization state information of the optical pulse signal, and outputs the polarization state measurement information to the monitoring module.

The attenuation module comprises a variable attenuation module, a third beam splitting module, a light energy measuring module and a fixed attenuation module;

the fixed attenuation module is used for receiving the other path of optical pulse signal output by the third beam splitting module, performing fixed attenuation processing on the optical pulse signal, and outputting the processed optical pulse signal to the first beam splitting module.

The monitoring module is also used for receiving the polarization state measurement information output by the polarization measurement module and the light energy value measurement result output by the light energy measurement module, performing feedback control on the polarization control module according to the polarization state measurement information, and performing feedback control on the variable attenuation module according to the coincidence counting result and the light energy value measurement result.

The signal source and delay submodule receives a control signal output by the data acquisition and processing module, generates a time sequence generation signal and outputs the time sequence generation signal to the light source module, and simultaneously generates a gate control signal and outputs the gate control signal to the single photon detector to be detected; triggering the light source module to generate a single photon pulse signal through the time sequence generation signal and outputting the single photon pulse signal to the single photon detector to be detected; the gate control signal is precisely delayed and then output to the single photon detector to be detected, so that the single photon detector to be detected can be controlled according to the delayed gate control signal; because the detection time of the single photon detector to be detected is short, extremely high requirements are put forward on the time sequence control precision and the signal synchronism of the system; the signal source and the delay submodule are realized by adopting a special time sequence chip and a special delay chip, can provide a multi-path precise clock signal with good synchronism for the system, and realize the precise delay adjustability of several picoseconds between the signals, thereby ensuring that the system can realize precise time sequence alignment and improving the parameter measurement precision of the single photon detector to be measured; the gate opening time of the single photon detector to be detected is accurately controlled through the gate control signal, and is matched with the time of the single photon pulse signal reaching the single photon detector to be detected, so that the synchronism of the system is ensured, and the measurement precision of the parameters of the single photon detector to be detected is improved; when the single photon detector to be detected receives the single photon pulse signal, counting the single photon pulse signal, and outputting the counting signal to the data acquisition and processing module, wherein the data acquisition and processing module obtains parameters of the single photon detector to be detected through analysis and processing according to the counting signal; the system can realize the human-computer interaction function, and the time sequence control precision and the signal synchronism of the system are ensured through the signal source and the delay submodule, so that the measurement precision of the parameters of the single photon detector to be measured is improved.

When the signal source and delay submodule receives the control signal output by the control and data processing module, the signal source and delay submodule not only generates a time sequence generation signal and a gate control signal, but also generates a start signal, outputs the start signal to the time-amplitude conversion measuring module after precise delay processing, and starts timing after the time-amplitude conversion measuring module receives the start signal; after the amplitude conversion measurement module receives a counting signal sent by the single photon detector to be detected, the counting signal is used as a stop signal, timing is suspended, timing duration of timing starting time and timing stopping time is calculated, the timing duration signal is output to the control and data processing module, and the control and data processing module analyzes and calculates parameters of the single photon detector to be detected according to the timing duration signal; the counting signals are pulse signals, and the number of the counting pulse signals needs to be obtained for calculating the parameters of the single photon detector to be detected, so that the number of the counting pulse signals is recorded by the amplitude conversion measuring module when the counting pulse signals are received, and the number of the counting pulse signals and the timing duration signals are simultaneously output to the control and data processing module for analysis and calculation, so that the parameters of the single photon detector to be detected are obtained.

The optical pulse signal generator adopts a picosecond pulse laser to output an initial optical signal after receiving a time sequence generation signal, the initial optical pulse signal is attenuated through an attenuation module, the energy of the optical pulse signal is attenuated to a single photon magnitude order to meet the requirement of single photon preparation, then the optical pulse signal subjected to attenuation processing is output to a first beam splitting module, the first beam splitting module is a first beam splitter and is used for splitting the input photonic pulse signal into two paths according to equal proportion, one path of optical pulse signal is output to a monitoring module, and the monitoring module is an HBT experimental system; taking the other path of optical pulse signal as the output end of the single photon source, and outputting the single photon pulse signal to the single photon detector to be detected; after receiving the optical pulse signals output by the first beam splitting module, the monitoring module performs coincidence counting operation on the optical pulse signals, and mapping the coincidence counting result and the average photon number of the optical pulse signals by using a mapping relation of a pre-calibrated coincidence counting result and the average photon number of the optical pulse signals to obtain the average photon number information of the single photon pulse signals; because the first beam splitter divides the optical pulse signals into two paths according to equal proportion, and the two paths of optical pulse signals are equivalent to each other, the state of the single photon source preparation system output state can be represented by the other path of single photon pulse signals for output according to the result output by the monitoring module, and the real-time monitoring of the single photon source preparation system output state is completed, wherein the coincidence counting operation is the prior art, and is not repeated in the specification; by the technical improvement, the number of single photons generated by a single photon source is monitored in real time, and the accuracy of the number of the single photons generated by the system is ensured.

The fourth beam splitting module is a fourth beam splitter; after receiving the optical pulse signal output by the first beam splitter, the fourth beam splitter further divides the optical pulse signal into two paths according to the equal proportion, outputs one path of optical pulse signal to the first single-photon detector, outputs the other path of optical pulse signal to the second single-photon detector, counts and detects the photon number in the optical pulse signal through the first single-photon detector and the second single-photon detector, outputs a photon counting result to the data processing unit, performs coincidence counting operation on the counting results of the two single-photon detectors by the data processing unit, and maps and obtains the average photon number information of the single-photon pulse signal and outputs the average photon number information of the single-photon signal to the control and data processing module by using the mapping relation between the coincidence counting result and the average photon number of the single-photon pulse signal, which is calibrated in advance, by using the nondetachability of photons; by adopting the structure of the monitoring module, the average photon number in the output single photon pulse signal can be accurately monitored on the photon magnitude, so that the real-time monitoring of the state of the single photon source output single photon pulse signal is completed.

The light path selection module is an optical switch, the optical switch receives an initial optical pulse signal output by the picosecond pulse laser, and the optical pulse signal is selectively output to the polarization control module or is selectively directly output to the attenuation module, so that the whole system can selectively generate a single photon pulse signal with a polarization state or a single photon pulse signal without the polarization state to meet the actual diversified output requirements; when the polarization control module receives the optical pulse signal output by the optical switch and controls the optical pulse signal to reach any required polarization state, the optical pulse signal with the polarization state is output to a second beam splitting module, the second beam splitting module is a second beam splitter, the second beam splitter divides the optical pulse signal into two paths according to the proportion of 10:90, 10% of the optical pulse signal is output to the polarization measurement module, and 90% of the optical pulse signal is output to the attenuation module; the polarization measurement module receives the optical pulse signal output by the second beam splitter, measures the polarization state of the optical pulse signal, and outputs the polarization state measurement information to the data processing unit in the monitoring module, the data processing unit judges whether the angle of the polarization state in the optical pulse signal is too large or too small according to the polarization state measurement information, if the angle of the polarization state in the optical pulse signal is too large, the polarization control module is subjected to polarization feedback control to reduce the angle of the polarization state, if the angle of the polarization state is too small, the polarization control module is subjected to polarization feedback control to increase the angle of the polarization state, and therefore the polarization state in the optical pulse signal is adjusted, and the control of the polarization state is more accurate and stable.

When the optical pulse signal enters the variable attenuation module through the second beam splitter or enters the variable attenuation module through the optical switch, the variable attenuation module performs variable attenuation on the energy of the optical pulse signal, so that the flexible control on the energy of the output optical pulse signal is realized; after the optical pulse signal enters a third beam splitting module through the variable attenuation module, the third beam splitting module is a third beam splitter, the third beam splitter divides the optical pulse signal into two paths according to the proportion of 99:1, 99% of the optical pulse signal is output to the optical energy measuring module, and 1% of the optical pulse signal is output to the fixed attenuation module; after the optical energy measuring module receives the optical pulse signal output by the third beam splitter, measuring the energy in the optical pulse signal, and outputting the optical energy value measuring result in the optical pulse signal to a data processing unit in the monitoring module; when the fixed attenuation module receives the optical pulse signal output by the third beam splitter, the fixed attenuation module accurately attenuates the optical pulse signal, so that the energy of the attenuated optical pulse signal reaches the single photon magnitude and is output to the first beam splitter; according to the technical scheme, after attenuation processing of the optical pulse signal is completed, the single photon magnitude optical pulse signal is obtained, photon energy is measured in proportion through the optical energy measuring module, the optical energy value measuring result is input into the data processing unit of the monitoring module, and the data processing unit performs feedback control on the variable attenuation module.

The data processing unit in the monitoring module judges whether the angle of the polarization state in the optical pulse signal is too large or too small according to the polarization state measurement information, if so, the polarization control module is subjected to polarization feedback control to reduce the angle of the polarization state, if not, the polarization control module is subjected to polarization feedback control to increase the angle of the polarization state, so that the angle of the polarization state in the optical pulse signal is adjusted, the control of the polarization state is more accurate and stable, in addition, the data processing unit in the monitoring module calculates the output energy of the optical pulse signal according to a certain proportion according to the measurement result of the optical energy value, and simultaneously, the data processing unit combines the coincidence counting result of the optical pulse signal input into the monitoring module to perform energy feedback control on the variable attenuation module, adjusts the multiple of the energy attenuation of the optical pulse signal, and ensures the stability of single photon pulse.

In the above embodiment, the calibration method calibrated in advance according to the mapping relationship between the counting result and the average photon number of the single optical pulse signal includes the following steps:

s202: supposing that the single-photon pulse signal is divided into two paths after passing through a beam splitter with the beam splitting ratio of S1: S2, the two paths of single-photon pulse signal light respectively enter a first single-photon detector and a second single-photon detector, and meanwhile, the response efficiency of the first single-photon detector and the response efficiency of the second single-photon detector to the single-photon pulse signal containing n photons are respectively

and η_2nThe dark counting rates of the two single photon detectors are respectively R1_darkAnd R2_darkIn the case where the gating frequency is R, the probability of occurrence of dark count noise every time the door is opened is as shown in equation (2):

and

are respectively:

outputting an expected value g according to the second-order autocorrelation function obtained in step S204²And (mu) mapping with the single photon pulse signal average photon number mu to obtain a mapping relation which accords with the counting result and the single photon pulse signal average photon number.

According to the principle of coincidence counting, if and only if two detectors have counting pulse signals to output, the coincidence counting outputs a value 1, and the rest condition outputs 0; meanwhile, the working characteristics of the single-photon detector are analyzed, and the counting pulse output by the single-photon detector can be divided into three conditions, namely a photon counting pulse generated after responding to an input single-photon pulse signal, a back pulse caused by previous response and a dark counting pulse randomly generated by the single-photon detector; the first type is an effective pulse to be measured, and the second type and the third type are counting pulses generated due to the self characteristics of the single-photon detector, namely noise generated by the single-photon detector; using P1_noiseAnd P2_noiseThe noise generated by the two single photon detectors is measured, and meanwhile, under the condition of no external photon input, the probability of outputting counting pulses by the detectors within one-time door opening time mainly comprises dark counting noise and rear pulse noise, so that a formula (3) can be obtained; when the single photon pulse signal input into the monitoring module, namely the HBT system, only contains 0 photon, the output of the detector is only influenced by thermal noise and rear pulse, and the probability of coincidence counting output 1 is shown in a formula (5); when the single photon pulse signal input into the HBT system only contains 1 photon, the photon only enters one of the two single photon detectors, and the probability of the coincidence counting output 1 is shown in a formula (6); when the single photon pulse signal input to the HBT system contains only 2 photons, there are three cases: 2 photons all enter a first single photon detector; 1 photon enters a first single photon detector, and the other 1 photon enters a second single photon detector; 2 photons all enter a second single photon detector; therefore, the probability of coincidence with count output 1 is as shown in equation (7); according to the formulas (5), (6) and (7), it is possible to deduceGiving formula (8); according to the coincidence counting principle, the photon counting results output by the first single-photon detector and the second single-photon detector are coincidently counted to obtain a second-order autocorrelation function output expected value g of the single-photon pulse signal²(mu), the value is also a second-order correlation function value of the single-photon pulse signal obtained by the monitoring module through coincidence counting, therefore, through the formula (4), the relation between the average photon number mu of the single-photon pulse signal and the output expected value of the second-order autocorrelation function of the single-photon pulse signal can be obtained, the average photon number mu of the single-photon pulse signal can be correspondingly obtained through the output expected value of the second-order autocorrelation function of the single-photon pulse signal, mapping between the coincidence counting result and the average photon number of the single-photon pulse signal is realized, and the mapping relation between the coincidence counting result and the average photon number of the single-photon pulse signal is.

In the parameter measurement process of the single photon detector to be measured, under the coordination control of the control and data processing module, the parameter measurement system of the single photon detector to be measured controls the signal source and the delay submodule to synchronously send three clock signals S1, S2 and S3 which respectively correspond to the time sequence generation signal, the gating signal and the start signal, the rising edges among the three signals are kept synchronous, and the clock frequency of S2 and S3 is a plurality of times of the clock frequency of S1; connecting S1 with an external trigger interface of a light source module, connecting S2 with a gate control signal input port of the single photon detector to be measured, taking S3 as a starting signal of a time-amplitude conversion measuring module, and precisely delaying the signals of S2 and S3 by a certain length;

because the main parameters of the single photon detector to be detected comprise single photon detection efficiency, detection efficiency linearity, dark counting rate, detector dead time, rear pulse probability, time jitter and polarization responsivity, after the number of counting pulse signals and timing duration signals enter the control and data processing module, the parameters can be obtained through analysis and calculation:

the detection efficiency of the single photon detector to be detected is the ratio of the number of photons actually measured by the detector to the number of photons reaching the detector, in the measurement process of the detection efficiency of the single photon detector to be detected, a measurement system triggers a single photon source to generate periodic single photon pulses through S1, the single photon pulses are input into the single photon detector to be detected, and after precise delay, the single photon pulses trigger the single photon detector to be detected to open a door when reaching the detector; s3 is output to the time-amplitude conversion measurement module after precise time delay, the counting signal generated by the single photon detector to be measured is input into the time-amplitude conversion measurement module as a stop signal, and at the moment, the time-amplitude conversion measurement module records the time interval of the time of the counting signal reaching the time-amplitude conversion measurement module relative to the time of S3 reaching; after the system is tested for a certain time, the control and data processing module counts the number of counting pulses output by the single photon detector to be tested, and corrects the result according to the statistical characteristic of the single photon source outputting the single photon pulse, so that the detection efficiency parameter to be measured can be obtained.

The detection efficiency linearity refers to the maximum deviation between the linear relation and the change relation of the detection efficiency of the detector along with the number of incident photons of the pulse; firstly, the system triggers a single photon source to generate periodic single photon pulses through S1, controls the average photon number generated by a light source module to be 0.1 through monitoring the light source module by a control and data processing module, inputs the single photon pulses into a single photon detector to be detected, and triggers the single photon detector to be detected to open a door when the single photon pulses reach the detector after precise time delay of S2; s3 is output to the time-amplitude conversion measurement module after precise time delay, the counting signal generated by the single photon detector to be measured is input into the time-amplitude conversion measurement module as a stop signal, and at the moment, the time-amplitude conversion measurement module records the time interval of the time of the counting signal reaching the time-amplitude conversion measurement module relative to the time of S3 reaching; after the measurement system is tested for a certain time, the control and data processing module counts to obtain the number of counting pulses output by the single photon detector to be tested; and finely adjusting the output state of the light source module to ensure that the average photon number output by the light source module is 0.2 photon, 0.3 photon, 0.4 photon and 0.5 photon respectively, repeating the process, connecting the results to form a linear equation set, solving the linear equation set to obtain the detection efficiency of the single photon detector to be detected on pulses with different photon numbers, thus obtaining the maximum deviation, namely the linearity, and finally performing statistical correction on the result.

The dark counting refers to the output of counting pulses generated by the single photon detector to be tested under the condition of no photon input, and the testing only needs to acquire the number of the counting pulses output by the single photon detector to be tested within a period of time under the condition of no input optical signal, calculate the number of the average counting pulses output in unit time, and obtain the dark counting rate of the single photon detector to be tested.

The dead time is the minimum time interval required by the single photon detector to be measured to respond to two adjacent photon pulses and can be regarded as the reciprocal of the maximum counting rate of the single photon detector to be measured, and therefore, the measurement of the dead time of the single photon detector to be measured is equivalent to the measurement of the maximum counting rate of the single photon detector to be measured. The method comprises the steps that firstly, S1 with low frequency to high frequency is triggered by a measuring system to trigger a light source module to generate periodic single photon pulses, a control and data processing module controls a monitoring module to adjust the output energy of the single photon pulses, and after each single photon pulse is input into a single photon detector to be measured, the probability of triggering the single photon detector to be measured to output counting pulses is 1, namely, the state close to saturated input is achieved; s2, after precise time delay, triggering the single photon detector to be tested to open the door at the moment when the single photon pulse reaches the detector; s3 is output to the time-amplitude conversion measurement module after precise time delay, the counting signal generated by the single photon detector to be measured is input into the time-amplitude conversion measurement module as a stop signal, and at the moment, the time-amplitude conversion measurement module records the time interval of the time of the counting signal reaching the time-amplitude conversion measurement module relative to the time of S3 reaching; after the measurement system is tested for a certain time, the control and data processing module counts to obtain the variation relation of the frequency of the counting pulse output by the single photon detector to be tested along with the external trigger frequency S1, finds out the position of the first inflection point, namely the maximum counting rate of the detector, and takes the reciprocal of the maximum counting rate as the dead time of the single photon detector to be tested.

The rear pulse probability refers to that after the avalanche effect of the single photon detector to be measured occurs last time, the residual carriers are accelerated again, and a counting pulse related to the last counting pulse occurs, and is called as a rear pulse. The measuring process of the measuring system for the rear pulse comprises the following steps: firstly, a measuring system triggers a light source module to generate periodic single photon pulses by S1 with a certain frequency, and controls a monitoring module to regulate the output energy of the single photon pulses through a control and data processing module, so that after each series of single photon pulses are input into a single photon detector to be detected, the probability of triggering the single photon detector to be detected to output counting pulses is 1, namely, the state close to saturation input is achieved; inputting single photon pulses into the single photon detector to be detected, controlling the signal frequency of S2 and S3 to be more than 10 times of the signal frequency of S1, and triggering the single photon detector to be detected to open a door when the single photon pulses reach the detector after the S2 is precisely delayed; s3 is output to the time-amplitude conversion measurement module after precise time delay, the counting signal generated by the single photon detector to be measured is input into the time-amplitude conversion measurement module as a stop signal, and at the moment, the time-amplitude conversion measurement module records the time interval of the time of the counting signal reaching the time-amplitude conversion measurement module relative to the time of S3 reaching; after the measurement system is tested for a certain time, the control and data processing module counts to obtain the output condition of the counting pulse output by the single photon detector to be tested; the occurrence position of the back pulse generally follows the first response photon pulse, so the back pulse probability of the single photon detector to be detected can be obtained through the statistics of the correlation relation of the back pulse on time.

The time of the single photon detector to be measured from the time when photons are incident on a photosensitive surface of the detector to the time when a macroscopic current is generated and is identified by an external detection circuit is called counting time. The measurement of the time jitter, at first the measurement system triggers the light source module to generate periodic single photon pulses with a certain frequency of S1, the monitoring module is controlled by the control and data processing module to regulate the output energy of the single photon pulses, so that after each single photon pulse is input into the single photon detector to be measured, the probability of triggering the single photon detector to be measured to output counting pulses is 1, namely the state close to saturated input is achieved; s2, after precise time delay, triggering the single photon detector to be tested to open the door at the moment when the single photon pulse reaches the detector; s3 is output to the time-amplitude conversion measurement module after precise time delay, the counting signal generated by the single photon detector to be measured is input into the time-amplitude conversion measurement module as a stop signal, and at the moment, the time-amplitude conversion measurement module records the time interval of the time of the counting signal reaching the time-amplitude conversion measurement module relative to the time of S3 reaching; after the measurement system is tested for a certain time, the control and data processing module counts the time interval recorded by the time-amplitude conversion measurement module, and the time interval is corrected as the time jitter parameter to be measured.

The response efficiency of the single photon detector to be tested to photons with different polarization states is called the polarization responsivity of the detector. The measurement essence of the polarization responsivity of the single photon detector to be measured is the same as the measurement mode of the detection efficiency, and the difference lies in the difference of the polarization states of incident photons, so that the measurement process of the polarization responsivity of the single photon detector to be measured is as follows: firstly, a system control S1 triggers a light source module to generate periodic single photon pulses, a control and data processing module controls a monitoring module to adjust a polarization control module to enable the output single photon pulses to reach a specific polarization state, and meanwhile, the control and data processing module monitors the light source module to control the average photon number generated by the light source module to be 0.1; inputting the pulse into a detector to be detected, and triggering the single photon detector to be detected to open a door when the single photon pulse reaches the detector after S2 is precisely delayed; s3 is output to the time-amplitude conversion measurement module after precise time delay, the counting signal generated by the single photon detector to be measured is input into the time-amplitude conversion measurement module as a stop signal, and at the moment, the time-amplitude conversion measurement module records the time interval of the time of the counting signal reaching the time-amplitude conversion measurement module relative to the time of S3 reaching; after the measurement system is tested for a certain time, the control and data processing module counts to obtain the number of counting pulses output by the single photon detector to be tested, and corrects the result according to the statistical characteristics of the single photon pulses to obtain the detection efficiency parameter of the single photon detector to be tested in the polarization state; changing the polarization state of the single photon pulse, and repeating the process to obtain the polarization responsivity of the single photon detector to be tested; the specific calculation method for the parameters of the 7 single photon detectors to be measured is the prior art, and is not described in detail in this specification.

Example 2:

the embodiment provides a single photon detector parameter measurement method, which adopts the single photon detector parameter measurement system to perform measurement, and the method comprises the following steps:

Further, step S4 includes the steps of:

and

are respectively:

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.

Claims

1. A single photon detector parameter measurement system comprises a light source module, a data acquisition and processing module and a display control module:

the circuit is characterized by also comprising a signal source and a delay submodule;

2. The system of claim 1 in which said data acquisition and processing module includes a control and data processing module and a time-amplitude conversion measurement module;

3. The single photon detector parameter measuring system of any one of claim 2 in which said light source module includes an optical pulse signal generator, an attenuation module, a first beam splitting module and a monitoring module;

4. The single photon detector parameter measuring system of claim 3, wherein said monitoring module comprises a fourth beam splitting module, a first single photon detector, a second single photon detector and a data processing unit;

5. The single photon detector parameter measurement system of claim 4 in which said light source module further includes a polarization module; the polarization module comprises a light path selection module, a second beam splitting module, a polarization control module and a polarization measurement module;

6. The single photon detector parameter measuring system of claim 5 in which said attenuation module comprises a variable attenuation module, a third beam splitting module, a light energy measuring module and a fixed attenuation module;

7. The system of claim 6 in which said monitoring module is further adapted to receive polarization state measurement information from said polarization measurement module and optical energy measurement results from said optical energy measurement module, to feedback control said polarization control module based on said polarization state measurement information, and to feedback control said variable attenuation module based on said coincidence count and said optical energy measurement results.

8. A single photon detector parameter measuring method, characterized in that a single photon detector parameter measuring system according to any one of claims 6 to 7 is used for measurement, the method comprising the steps of:

9. The single photon detector parametric measurement method of claim 8, wherein the step S4 comprises the steps of:

10. The method as claimed in claim 9, wherein the calibration method based on the mapping relationship between the counting result and the average photon number of the single-light-pulse signal, which is calibrated in advance, comprises the following steps:

s203: suppose the probability of the back pulse of the first single-photon detector and the probability of the back pulse of the second single-photon detector are respectively P1_spAnd P2_spThe noise probability of the first single-photon detector and the noise probability of the second single-photon detector are respectively P1_noiseAnd P2_noiseAccording to the counting operation characteristics of the single-photon detectorTo obtain:

P1_noise＝P1_sp∑[(P_(μ',n))η_1n+P1_dark]

P2_noise＝P2_sp∑[(P_(μ”,n))η_1n+P2_dark](3)

where N is 1,2,3, …, N is the maximum value of photon number contained in photon pulse, P is₁ ⁿThe probability of coincidence with the count output 1 when the photon pulse contains n photons;

and

are respectively: