A test system for superconducting array single-photon detectors

Abstract

This paper proposes a testing system for superconducting array single-photon detectors, comprising a test light source, a refrigerator, and a cryogenic readout circuit. This system can perform single-photon pulse response and spectral response tests in different wavelength bands, and is capable of variable-temperature testing under varying temperature conditions. The system utilizes a T-type cryogenic bias tee and cryogenic radio frequency amplifier to minimize the transmission attenuation of test signals, providing a novel approach for testing large-scale superconducting array detector chips. All components within the system are commercially available and, after optical path calibration and installation, can operate continuously and stably. This system is suitable for testing superconducting array single-photon detectors.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting array single-photon detection, and in particular relates to a testing system for a superconducting array single-photon detector. Background Art

[0002] Superconducting detectors, due to their high single-photon detection efficiency, low temporal jitter, low dark count rate, and ultrafast response time, have recently been widely used in fields such as quantum computing, quantum communication, quantum weak measurement, and frequency up-conversion detection. With the advancement of science and technology, various fields are placing new demands on the performance of superconducting detectors, requiring devices with photon number resolution and imaging capabilities. Consequently, superconducting array single-photon detectors (SPDs) are attracting increasing attention. Furthermore, compared to the established superconducting nanowire single-photon detectors (SNSPDs), superconducting detectors of different systems are gradually entering the research field. For example, high-temperature superconductors such as iron-based superconductors and copper oxide superconductors have been fabricated using these systems. To successfully characterize the single-photon detection performance, crosstalk between pixels, and spectral response of SNSPDs, it is necessary to build a suitable test system capable of multi-pixel testing, multi-band testing, and low test signal transmission loss, providing support for the development of SNSPDs. Summary of the Invention

[0003] (1) Technical issues to be solved

[0004] The present invention provides a testing system for a superconducting array single-photon detector to solve the technical problem of testing the superconducting array single-photon detector.

[0005] (2) Technical solution

[0006] In order to solve the above technical problems, the present invention proposes a test system for a superconducting array single-photon detector, which includes a test light source, a refrigerator and a low-temperature readout circuit; wherein,

[0007] The test light source includes a visible light CCD camera, a CCD camera field illumination light source, a visible light semi-transparent and semi-reflective mirror, a blackbody light source, a monochromator, a first collimator lens barrel, a first reflector, a laser light source, a pluggable attenuator, an adapter, a wide-spectrum optical fiber, an optical fiber beam expander, a second collimator lens barrel, a second reflector, a multi-layer integrated lens barrel and a total reflection objective lens; wherein, the visible light semi-transparent and semi-reflective mirror, the first reflector and the second reflector are integrated in the multi-layer integrated lens barrel; the CCD camera field illumination light source emits visible light, which passes through the visible light semi-transparent and semi-reflective mirror, and a part of the visible light enters the total reflection objective lens, is focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip, and then is reflected into the visible light CCD camera to find the pixel to be tested in the field of view; the blackbody light source emits light in a wide spectrum, and photons of different wavelengths enter the monochromator, By adjusting the grating of the monochromator, photons of a specific wavelength are filtered out and then irradiated onto the first reflector through the first collimator lens barrel. After being reflected by the first reflector, the photons of the specific wavelength enter the total reflection objective lens, are focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip, and cooperate with the low-temperature readout circuit to realize the spectral response test of the superconducting array single-photon detector; the laser light source emits pulsed monochromatic light, which is attenuated to the quasi-single-photon source level by the pluggable attenuator, enters the second collimator lens barrel through the adapter, wide-spectrum optical fiber and optical fiber beam expander, and then enters the total reflection objective lens through the second reflector, and is focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip. Cooperating with the low-temperature readout circuit, the single-photon pulse response test and crosstalk test of the superconducting array single-photon detector in different bands are realized;

[0008] The refrigerator includes a light window cover, a sample holder, a secondary cold head, a bellows, a high-precision three-dimensional translation stage, a temperature sensor, a temperature heater, an oxygen-free copper tape, a primary cold head, a radiation shield, an SMA connector, a molecular pump, a compressor, and a water cooler. The sample holder is fixed on the secondary cold head, a 50Ω matched microstrip line is used inside the sample holder, and the input and output ports use SMA or SMP interfaces. The superconducting array single-photon detector is attached to the sample holder, and the electrodes of the pixels to be measured are connected to the sample holder through lead connections, and the sample holder is connected to the low-temperature readout circuit through the SMA interface. The secondary cold head is connected to the high-precision three-dimensional translation stage through the bellows to achieve high-precision positioning of the pixels to be measured. In the case of multi-channel testing, the high-precision three-dimensional translation stage is adjusted to position different pixels to be measured. The element is switched to the focused light spot to realize continuous testing of different pixels of the superconducting array single-photon detector; the secondary cold head is connected to the primary cold head through an oxygen-free copper tape, and the primary cold head is connected to an external compressor, and heat exchange is performed through helium to achieve a cooling effect; the radiation shield is used to cover the superconducting array single-photon detector chip to isolate external radiation; the light window cover is installed on the top of the radiation shield to provide a light window for the superconducting array single-photon detector; the molecular pump is used to pump the internal space of the refrigerator system to a low vacuum environment; the compressor is used to provide power for the refrigeration cycle; the water cooler is used to cool the compressor; the temperature heater is placed on the secondary cold head, and the test temperature is controlled by an external temperature controller to heat the low-temperature cavity to the set temperature; the temperature sensor is used to monitor the temperature of the test system in real time;

[0009] The low-temperature readout circuit includes a DC voltage source, a 100kΩ protection resistor, a T-type low-temperature bias device, a low-temperature RF amplifier, a low-temperature RF coaxial line, a room-temperature RF coaxial line and an oscilloscope; among them, the DC voltage source sequentially powers the superconducting array single-photon detector through the 100kΩ protection resistor and one end of the T-type low-temperature bias device. Under the irradiation of a pulsed light source, the response signal of the detector chip enters the low-temperature RF amplifier through the other end of the T-type low-temperature bias device for amplification; a low-temperature RF coaxial line is selected inside the low-temperature cavity, and a room-temperature RF coaxial line is selected outside the low-temperature cavity; the amplified signal is input into an external oscilloscope through the low-temperature RF coaxial line and the room-temperature RF coaxial line to read the signal, and the inside and outside of the low-temperature cavity are connected through an SMA interface.

[0010] Furthermore, the molecular pump is a compound molecular pump or a turbo molecular pump, which is used to pump the internal space of the refrigerator system to 10 -5 pa low vacuum environment.

[0011] Furthermore, the oxygen content of the oxygen-free copper strip is no more than 0.03%, the total impurity content is no more than 0.05%, and the purity of the copper is greater than 99.95%.

[0012] Furthermore, the high-precision three-dimensional translation stage can realize manual adjustment movement in the XYZ three axes, with a minimum movement step of ≤1μm and a movement range of ≥5mm.

[0013] Furthermore, the inside and outside of the low-temperature chamber are connected via an SMA interface, and both ends of the SMA interface are SMA male connectors.

[0014] Furthermore, the low-temperature radio frequency amplifier is made of SiGe material.

[0015] Furthermore, the cryogenic RF coaxial line has 50Ω impedance matching under low temperature conditions.

[0016] Furthermore, the room temperature RF coaxial line has 50Ω impedance matching under room temperature conditions.

[0017] Furthermore, the bandwidth of the oscilloscope covers 100kHz-10GHz, which is used to read out the test response signal of the chip.

[0018] (3) Beneficial effects

[0019] This paper proposes a testing system for superconducting array single-photon detectors, comprising a test light source, a refrigerator, and a cryogenic readout circuit. This system can perform single-photon pulse response and spectral response tests in different wavelength bands, and is capable of variable-temperature testing under varying temperature conditions. The system utilizes a T-type cryogenic bias tee and cryogenic radio frequency amplifier to minimize the transmission attenuation of test signals, providing a novel approach for testing large-scale superconducting array detector chips. All components within the system are commercially available and, after optical path calibration and installation, can operate continuously and stably. This system is suitable for testing superconducting array single-photon detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the test light source composition in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the composition of a refrigerator in an embodiment of the present invention;

[0022] Figure 3 Schematic diagram of the low-temperature readout circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings and examples.

[0024] This invention proposes a testing system for superconducting array single-photon detectors, primarily consisting of a test light source, a temperature-variable refrigerator, and a cryogenic readout circuit. The system utilizes a fully reflective objective lens to bring incident pulsed light sources of varying wavelengths into focus via a free-range optical path. The temperature-variable refrigerator adjusts the required test temperature, and a three-axis translation stage achieves high-precision positioning, illuminating the focused light spot onto the pixel under test. Finally, a cryogenic readout circuit generates chip test signals, enabling single-photon pulse response and spectral response testing of superconducting array single-photon detectors across different wavelength bands. All components within the system are commercially available and, after optical path calibration and installation, provide continuous and stable operation.

[0025] like Figure 1 As shown, the test light source mainly includes a visible light CCD camera 1-1, a CCD camera field illumination light source 1-2, a visible light semi-transparent semi-reflective mirror 1-3, a blackbody light source 1-4, a monochromator 1-5, a first collimating lens barrel 1-6, a first reflector 1-7, a laser light source 1-8, a pluggable attenuation plate 1-9, an adapter 1-10, a broadband optical fiber 1-11, an optical fiber beam expander 1-12, a second collimating lens barrel 1-13, a second reflector 1-14, a multi-layer integrated lens barrel 1-15 and a total reflection objective lens 1-16.

[0026] The visible light CCD camera 1-1 is used for real-time imaging, finding and aligning the photosensitive surface of the pixel to be measured. The visible light CCD camera 1-1 is a common commercial visible light CCD camera that can convert optical images into digital signal outputs and transmit them to the display, so that the situation of the optical path focus area can be observed; the CCD camera field illumination light source 1-2 is used to provide a stable illumination light source for the visible light CCD camera 1-1; the visible light semi-transparent and semi-reflective mirror 1-3 is used to reflect and transmit visible light, and can reflect half of the light and transmit half of the light. It is installed at a 45° angle to the optical path, so that the visible light CCD camera 1-1 can The pixels to be tested can be clearly seen; the blackbody light sources 1-4 have high-precision temperature control capabilities and can stably radiate photons of different wavelengths for system spectral response testing; the monochromator 1-5 can use a grating to disperse the complex mixed light generated by the blackbody light source 1-4 into quasi-monochromatic light, and output a series of independent monochromatic lights with sufficiently narrow spectral bandwidths as required; the first collimating lens barrel 1-6 and the second collimating lens barrel 1-13 are used to collimate the light beam; the surface of the first reflector 1-7 and the second reflector 1-14 are both coated with a layer of reflective material for reflecting the test light, and different types of reflectors can be selected according to different test wavelengths. Mirror, installed at a 45° angle to the optical path; laser light source 1-8 is used to generate a pulse light source, which can stably output the test light source. When testing the pulse response of the detector chip, different pulse widths and frequencies can be selected according to the response time of the array detector chip; pluggable attenuation plate 1-9 is used to attenuate the pulse light source output by the laser light source 1-8, and uses the reflection or absorption of light of a specific wavelength by the material to achieve the purpose of attenuating the light intensity. Through multi-stage attenuation, the light source is attenuated to the quasi-single photon level. The attenuation plate has the ability of quasi-continuous or continuous attenuation and is installed at a 90° angle to the optical path; adapter 1-10 is used for The spatial optical path is coupled into the broadband optical fiber 1-11; the broadband optical fiber 1-11 is used to transmit test photons, and can stably transmit photons of a specific wavelength, with the characteristics of low loss and low noise. A suitable broadband optical fiber 1-11 can be selected according to different laser light sources 1-8; the optical fiber expander 1-12 is used to expand and collimate the light beam output by the broadband optical fiber 1-11; the total reflection objective lens 1-16 is used to focus the optical path, and achieve confocal point for the entire spectrum from visible light to long-wave infrared; the multi-layer integrated lens barrel 1-15 is used to fix each layer of lenses to achieve pluggable function, and can also ensure the stability and repeatability of the optical path.

[0027] The visible light semi-transparent and semi-reflective mirror 1-3, the first reflector 1-7 and the second reflector 1-14 are integrated in the multi-layer integrated lens barrel 1-15, and each lens is designed to be pluggable and replaceable. According to the different wavelength light sources selected for the test, reflectors with different coating materials are selected to ensure that the optical path is compatible with the ultraviolet band to the long-wave infrared band.

[0028] The visible light emitted by the CCD camera field illumination light source 1-2 passes through the visible light semi-transparent and semi-reflective mirror 1-3. A portion of the visible light enters the total reflection objective lens 1-16, is focused and irradiated onto the photosensitive surface of the pixel to be measured on the superconducting array single-photon detector chip, and then is reflected back and enters the visible light CCD camera 1-1. With the help of a high-precision three-dimensional translation stage, the pixel to be measured is found in the field of view.

[0029] The blackbody light source 1-4 emits light of a wide spectrum, and photons of different wavelengths enter the monochromator 1-5. By adjusting the grating of the monochromator 1-5, photons of specific wavelengths are filtered out and then irradiated onto the first reflector 1-7 through the first collimating lens barrel 1-6. After being reflected by the first reflector 1-7, the photons of specific wavelength enter the total reflection objective lens 1-16, and are focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip. In conjunction with the low-temperature readout circuit, the spectral response test of the superconducting array single-photon detector is realized.

[0030] The pulsed monochromatic light emitted by the laser light source 1-8 is attenuated to the quasi-single-photon source level by the pluggable attenuator 1-9, enters the second collimating lens barrel 1-13 through the adapter 1-10, the wide-spectrum optical fiber 1-11 and the optical fiber beam expander 1-12, and then enters the total reflection objective lens 1-16 through the second reflector 1-14. It is focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip. In conjunction with the low-temperature readout circuit, the single-photon pulse response test and crosstalk test of the superconducting array single-photon detector in different bands are realized.

[0031] like Figure 2 As shown, the refrigerator mainly includes a light window cover 2-1, a sample holder 2-2, a secondary cold head 2-3, a bellows 2-4, a high-precision three-dimensional translation stage 2-5, a temperature sensor 2-6, a temperature heater 2-7, an oxygen-free copper strip 2-8, a primary cold head 2-9, a radiation shield 2-10, an SMA connector 2-11, a molecular pump 2-12, a compressor 2-13 and a water chiller 2-14.

[0032] Molecular pump 2-12 is used to pump the internal space of the refrigerator system to a low vacuum environment (10 -5pa), a compound molecular pump or a turbomolecular pump is selected; the compressor 2-13 is used to provide power for the refrigeration cycle, and the minimum temperature of the refrigerator system is reduced to about 4K through helium heat exchange; the water cooler 2-14 is used to provide constant temperature, constant flow, and constant pressure cooling water to the compressor 2-13 to cool the compressor 2-13. The temperature heater 2-7 is placed on the secondary cold head 2-3, and uses electrical energy to achieve the heating effect. The test temperature is controlled by an external temperature controller, and the low-temperature chamber is heated to the set temperature to achieve variable temperature testing of the system from 4K to room temperature. The temperature sensor 2-6 is used to monitor the temperature of the test system in real time. It can sense the temperature and convert it into a usable output signal, and can display the test temperature in real time. Its test range is from 4K to room temperature. The high-precision three-dimensional translation stage 2-5 can realize manual adjustment movement in the XYZ three axes, with a minimum movement step of ≤1μm and a movement range of ≥5mm.

[0033] The sample holder 2-2 is fixed to a secondary cold head 2-3. A 50Ω-matched microstrip line is used internally, and the input and output ports utilize SMA or SMP connectors. The number of paths on the sample holder 2-2 is designed appropriately based on the array size of the superconducting array single-photon detector chip. The superconducting array single-photon detector is attached to the sample holder 2-2. The electrodes of the pixels to be measured are connected to the sample holder 2-2 via wire leads. The sample holder 2-2 is connected to the cryogenic readout circuit via an SMA connector 2-1. The secondary cold head 2-3 is connected to a high-precision three-dimensional translation stage 2-5 via a bellows 2-4, enabling high-precision positioning of the pixels to be measured. For multi-path testing, the high-precision three-dimensional translation stage 2-5 is adjusted to switch different pixels to be measured into the focused beam spot, enabling sequential testing of different pixels in the superconducting array single-photon detector. The secondary cold head 2-3 is connected to the primary cold head 2-9 via an oxygen-free copper strip 2-8. The primary cold head 2-9 is connected to an external compressor 2-13, where heat exchange is performed via helium to achieve a cooling effect. The primary cold head 2-9 and the secondary cold head 2-3 exchange heat with the compressor 2-13 via helium, thereby lowering their own temperatures and providing a low-temperature environment for the test samples. The oxygen content of the oxygen-free copper strip 2-8 is no greater than 0.03%, the total impurity content is no greater than 0.05%, and the copper purity is greater than 99.95%. The radiation shield 2-10 covers the superconducting array single-photon detector chip, isolating it from external radiation. The optical window cover 2-1 is installed on top of the radiation shield 2-10 to provide an optical window for the superconducting array single-photon detector. The appropriate optical window can be selected for different test wavelengths.

[0034] like Figure 3 As shown, the low-temperature readout circuit mainly includes a DC voltage source 3-1, a 100kΩ protection resistor 3-2, a T-type low-temperature bias device 3-3, a low-temperature RF amplifier 3-4, a low-temperature RF coaxial line 3-5, a room-temperature RF coaxial line 3-6 and an oscilloscope / counter 3-7.

[0035] DC voltage source 3-1 is used to supply power to the outside world via a battery. It features low noise and stable output. The voltage output value can be set according to test conditions, either maintaining a fixed output value or continuously varying the output voltage. For example, a fixed output value is required when measuring a chip's pulse response, while a continuously varying voltage is required when measuring a chip's IV characteristic curve.

[0036] A DC voltage source 3-1 supplies power to the superconducting single-photon array detector (SPAD) through a 100kΩ protective resistor 3-2 and one end of a T-type cryogenic bias device 3-3. Under pulsed light, the detector chip's response signal flows through the other end of the T-type cryogenic bias device 3-3 and enters a cryogenic RF amplifier 3-4 for amplification. The amplified signal is then fed through a cryogenic RF coaxial cable 3-5 and a room-temperature RF coaxial cable 3-6 to an external oscilloscope / counter 3-7 for readout. To ensure low-loss signal transmission, a cryogenic RF coaxial cable 3-5 is used inside the cryogenic cavity, while a room-temperature RF coaxial cable 3-6 is used outside. The interior and exterior of the cryogenic cavity are connected via SMA connectors, each with a male SMA connector. These connectors are located around the cavity. The number of connectors installed can be selected based on the scale of the SAD and testing requirements.

[0037] The 100kΩ protection resistor 3-2 protects the chip from excessive voltage across it, potentially damaging it. The size of the protection resistor can be adjusted based on actual testing conditions. The T-type low-temperature bias tether 3-3, with its inductor and capacitor capable of operating at low temperatures, provides DC voltage to the chip and extracts its RF signal. The low-temperature RF amplifier 3-4, made of SiGe material, offers low noise and high gain. It can operate from temperatures ranging from 4K to room temperature, amplifying the chip's response signal. The low-temperature RF coaxial cable offers 50Ω impedance matching at low temperatures, resulting in low transmission loss and minimizing signal loss.

[0038] The room-temperature RF coaxial cable 3-6 has a 50Ω impedance match at room temperature, featuring low transmission loss and minimizing signal loss. The oscilloscope / counter 3-7 has a bandwidth covering 100kHz-10GHz and is used to read the chip's test response signal.

[0039] The specific method of testing using the test system of the present invention is as follows:

[0040] Focus the optical path on the photosensitive surface of the pixel to be measured: turn on the CCD camera field illumination light source 1-2, turn on the visible light CCD camera 1-1, insert the visible light semi-transparent and semi-reflective mirror 1-3 into the multi-layer integrated lens barrel 1-15, and do not insert the other mirrors; the light emitted by the CCD camera field illumination light source 1-2 is collimated by the lens barrel, reflected at the visible light semi-transparent and semi-reflective mirror 1-3, and illuminates the pixel of the array detector under the action of the total reflection objective lens 1-16; according to the reversible principle of the optical path, the reflected light is transmitted through the visible light semi-transparent and semi-reflective mirror 1-3 into the visible light CCD camera 1-1, and a clear image of the surface of the array detector is obtained under the visible light CCD camera 1-1; then, the pixel to be measured is moved to the light spot focused by the total reflection objective lens 1-16 through a high-precision translation stage.

[0041] Calibration of light intensity and optical path loss: Use a standard detector or optical power meter to measure the output power of the laser light source, connect the optical path, connect to the second reflector 1-14, and pass the optical path through the light window cover 2-1. Then place the standard detector or optical power meter at the focus of the total reflection objective lens 1-16 and test the final power. This can calibrate the loss of the entire optical path and pave the way for adjusting the light intensity in subsequent tests.

[0042] Test the spectral response of the array detector: After the optical path is focused on the pixel to be measured, turn off the CCD camera field illumination light source 1-2, turn on the blackbody light source 1-4 and the monochromator 1-5, insert the first reflector 1-7, and do not insert the other lenses into the optical path; obtain mid-infrared monochromatic light of different wavelengths by adjusting the monochromator 1-5, pass through the collimating lens barrel, and under the action of the first reflector 1-7 and the second reflector 1-14, focus the photons of different wavelengths through the total reflection objective lens 1-16 onto the photosensitive surface of the pixel to be measured; turn on the refrigerator to reach the test temperature, and use the low-temperature readout circuit to measure the spectral response of the array detector to different wavelengths.

[0043] Test the single-photon pulse response of the array detector: turn on the laser light source 1-8, focus the light source on the pixel to be tested, and attenuate the light source to the quasi-single-photon level through multi-stage attenuation; turn on the refrigerator, wait until the temperature reaches the set temperature, connect the low-temperature readout circuit, introduce the test signal into the oscilloscope / counter 3-7, measure the single-photon pulse response of the array detector, and obtain the pulse response time of the single-photon light array detector.

[0044] Crosstalk test of array detector: After testing the single photon response of the pixel, bias voltage is applied to the adjacent pixel to test the signal of the adjacent pixel to complete the crosstalk test.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A test system for a superconducting array single-photon detector, characterized in that: The test system includes a test light source, a refrigerator and a low-temperature readout circuit; wherein, The test light source includes a visible light CCD camera, a CCD camera field illumination light source, a visible light semi-transparent and semi-reflective mirror, a blackbody light source, a monochromator, a first collimator lens barrel, a first reflector, a laser light source, a pluggable attenuation plate, an adapter, a broadband optical fiber, an optical fiber beam expander, a second collimator lens barrel, a second reflector, a multi-layer integrated lens barrel and a total reflection objective lens; wherein the visible light semi-transparent and semi-reflective mirror, the first reflector and the second reflector are integrated in the multi-layer integrated lens barrel; the CCD camera field illumination light source emits visible light, and a portion of the visible light passes through the visible light semi-transparent and semi-reflective mirror and enters the total reflection objective lens, which is focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip, and then reflected into the visible light CCD camera to find the pixel to be tested in the field of view; the blackbody light source emits light in a broadband band, and photons of different wavelengths enter the monochromator By adjusting the grating of the monochromator, photons of specific wavelength are filtered out and then irradiated onto the first reflector through the first collimator lens barrel. After being reflected by the first reflector, the photons of specific wavelength enter the total reflection objective lens, are focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip, and cooperate with the low-temperature readout circuit to realize the spectral response test of the superconducting array single-photon detector; the laser light source emits pulsed monochromatic light, which is attenuated to the quasi-single-photon source level by the pluggable attenuator, enters the second collimator lens barrel through the adapter, wide-spectrum optical fiber and optical fiber beam expander, and then enters the total reflection objective lens through the second reflector, and is focused and irradiated onto the photosensitive surface of the pixel to be tested of the superconducting array single-photon detector chip. Cooperating with the low-temperature readout circuit, the single-photon pulse response test and crosstalk test of the superconducting array single-photon detector in different wavelength bands are realized; The refrigerator includes a light window cover, a sample holder, a secondary cold head, a bellows, a high-precision three-dimensional translation stage, a temperature sensor, a temperature heater, an oxygen-free copper strip, a primary cold head, a radiation shield, an SMA connector, a molecular pump, a compressor, and a water cooler; wherein, the sample holder is fixed on the secondary cold head, a 50Ω matched microstrip line is used inside the sample holder, and the input and output ports use SMA or SMP interfaces; a superconducting array single-photon detector is attached to the sample holder, and the electrodes of the pixels to be measured are connected to the sample holder through lead connections, and the sample holder is connected to the low-temperature readout circuit through the SMA interface; the secondary cold head is connected to the high-precision three-dimensional translation stage through the bellows to achieve high-precision positioning of the pixels to be measured. In the case of multi-channel testing, the high-precision three-dimensional translation stage is adjusted to position different pixels to be measured The pixel is switched to the focused light spot to achieve continuous testing of different pixels of the superconducting array single-photon detector; the secondary cold head is connected to the primary cold head through an oxygen-free copper tape, and the primary cold head is connected to an external compressor, and heat exchange is performed through helium to achieve a cooling effect; the radiation shield is used to cover the superconducting array single-photon detector chip to isolate external radiation; the light window cover is installed on the top of the radiation shield to provide a light window for the superconducting array single-photon detector; the molecular pump is used to pump the internal space of the refrigerator system to a low vacuum environment; the compressor is used to provide power for the refrigeration cycle; the water cooler is used to cool the compressor; the temperature heater is placed on the secondary cold head, and the test temperature is controlled by an external temperature controller to heat the low-temperature cavity to the set temperature; the temperature sensor is used to monitor the temperature of the test system in real time; The low-temperature readout circuit includes a DC voltage source, a 100kΩ protection resistor, a T-type low-temperature bias device, a low-temperature radio frequency amplifier, a low-temperature radio frequency coaxial line, a normal-temperature radio frequency coaxial line, and an oscilloscope. The DC voltage source sequentially powers the superconducting array single-photon detector through the 100kΩ protection resistor and one end of the T-type low-temperature bias device. Under the irradiation of a pulsed light source, the response signal of the detector chip enters the low-temperature radio frequency amplifier through the other end of the T-type low-temperature bias device for amplification. A low-temperature radio frequency coaxial line is selected inside the low-temperature cavity, and a normal-temperature radio frequency coaxial line is selected outside the low-temperature cavity. The amplified signal is input into an external oscilloscope through the low-temperature radio frequency coaxial line and the normal-temperature radio frequency coaxial line to read the signal. The inside and outside of the low-temperature cavity are connected via an SMA interface.

2. The test system according to claim 1, wherein: The molecular pump is a compound molecular pump or a turbo molecular pump, which is used to pump the internal space of the refrigerator system to 10 -5 pa low vacuum environment.

3. The test system according to claim 1, wherein: The oxygen content of the oxygen-free copper strip is no more than 0.03%, the total impurity content is no more than 0.05%, and the purity of copper is greater than 99.95%.

4. The test system according to claim 1, wherein: The high-precision three-dimensional translation stage can realize manual adjustment movement in XYZ three axes, with a minimum movement step of ≤1μm and a movement range of ≥5mm.

5. The test system according to claim 1, wherein: The interior and exterior of the low-temperature chamber are connected via an SMA interface, and both ends of the SMA interface are SMA male connectors.

6. The test system according to claim 1, wherein: The low-temperature radio frequency amplifier is made of SiGe material.

7. The test system according to claim 1, wherein: The low-temperature radio frequency coaxial line has 50Ω impedance matching under low-temperature conditions.

8. The test system according to claim 1, wherein: The room temperature radio frequency coaxial line has 50Ω impedance matching under room temperature conditions.

9. The test system according to claim 1, wherein: The bandwidth of the oscilloscope covers 100 kHz-10 GHz and is used to read the test response signal of the chip.

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