A TF-QKD method and detection end capable of performing polarization and time feedback

Abstract

The present invention proposes a TF-QKD method and a detection end capable of performing polarization and time feedback, which relate to the technical field of quantum communication. In the QKD debugging stage, a transmitting end sends a phase reference optical pulse to a detection end, and the detection end performs initial polarization adjustment and delay adjustment on the phase reference optical pulse; in the QKD operation stage, the transmitting end single-end sends a phase reference optical pulse and a quantum signal optical pulse with a coding period, and the detection end calculates the relative delay of the transmitting end to achieve delay calibration of the single-end sent optical pulse, and performs polarization feedback based on the count rate in the single-end sent time period, so that the count rate of the single-end sent optical pulse reaches a maximum value; compared with the prior art, the detector is removed at the detection end, which saves costs and reduces system complexity.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication technology, and in particular to a TF-QKD method and a detection end capable of performing polarization and time feedback. Background Art

[0002] In the TF-QKD protocol, in order to achieve stable interference between the optical pulses encoded by Alice and Bob at the transmitting end and Charlie at the detecting end, the polarization of the two light beams entering the interference must be consistent. However, the polarization direction of the optical pulse will change during the transmission of the optical fiber link, so the light at the detecting end needs to be polarized before entering the interference. Figure 1 It is an existing TF-QKD detection end. PBS1 and PBS2 can polarize and divide the incident light into two beams with perpendicular polarization directions: the light with the same polarization direction as PBS enters BS for interference, and is detected by single-photon detectors A1 and A2 after interference; while the light with the polarization direction perpendicular to the PBS enters single-photon detectors B1 and B2. The detection results of detectors A1 and A2 are used to calculate phase difference and code.

[0003] In TF-QKD, in order to improve the coding rate, it is expected that most of the light enters the interference for coding, and the polarization direction of the light before entering the PBS is as consistent as possible with the set direction of the PBS. Since the amount of polarization change in the link will change during the operation of QKD, in order to achieve this goal, it is necessary to detect the light at the vertical end of the PBS, and adjust the polarization controller according to the detection results so that the count rate at the vertical end of the PBS is lower than a certain set value to achieve polarization feedback. In TF-QKD, in order to achieve precise interference, the time when Alice and Bob's light pulses arrive at the BS must be precisely consistent. Even if the delay calibration is performed during the QKD debugging phase, the delay may vary to a certain extent during the QKD operation phase (in the order of ps to ns), resulting in the inability of the light pulses to interfere accurately, thereby reducing the coding rate. For this reason, it is necessary to detect a portion of the light pulses that have not interfered, and based on the detection results, Alice and Bob adjust the delay to make the light pulses arrive at the interference at the same time (that is, the rising edge of the pulse and the waveform are aligned) to achieve time feedback. Polarization feedback and time feedback require the detection results of light pulses that have not interfered. Figure 1 In the scheme, the detection results of B1 and B2 are used for polarization feedback and time feedback.

[0004] exist Figure 1 In the scheme, the counting rates of detectors B1 and B2 are counted and fed back to the transmitters Alice and Bob. Alice and Bob adjust the polarization of the light pulse according to the counting rates, so that the counting rates of detectors B1 and B2 are lower than a certain set value, thus realizing polarization feedback. Figure 1In the scheme, the detection results of detectors B1 and B2 are periodically counted, and the rising edge of the pulse is located based on the statistical results. Alice and Bob adjust the delay to align the rising edge and perform time feedback. The purpose of polarization feedback is to reduce the count rate of detectors B1 and B2; however, since the detection results of detectors B1 and B2 are used for time feedback, Figure 1 In the scheme, the counting rates of detectors B1 and B2 cannot be too low and must be maintained at a certain level.

[0005] The disadvantages of the existing scheme are: (1) In addition to the detector used for coding, two single-photon detectors, detectors B1 and B2, are used, which increases the cost and the complexity of the system; (2) The detection results of detectors B1 and B2 are used for delay calibration, so detectors B1 and B2 need to maintain a certain counting rate, so that the counting rate of detectors A1 and A2 cannot reach the maximum, thereby reducing the coding rate. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a TF-QKD method capable of performing polarization and time feedback, including a QKD debugging phase and a QKD operation phase;

[0007] In the QKD debugging stage, the transmitting end sends a phase reference optical pulse to the detecting end, and the detecting end performs initial polarization adjustment and delay adjustment on the phase reference optical pulse;

[0008] In the QKD operation phase, the transmitting end single-end transmits a phase reference optical pulse and a quantum signal optical pulse with a coding period, the detecting end calculates the relative delay of the transmitting end, realizes the delay calibration of the single-end transmitted optical pulse, and performs polarization feedback based on the detection result of the optical pulse count rate in the single-end transmitted time period, so that the single-end transmitted optical pulse count rate reaches the maximum value.

[0009] Furthermore, the transmitting end includes an Alice end and a Bob end, and the Alice end and the Bob end send phase reference optical pulses and quantum signal optical pulses according to a coding period; the coding period of the phase reference optical pulse includes a time period in which the Alice end sends a phase reference optical pulse and the Bob end does not send a phase reference optical pulse, and a time period in which the Bob end sends a phase reference optical pulse and the Alice end does not send a phase reference optical pulse, and the detection result of the time period in which the Alice end sends the phase reference optical pulse and the Bob end does not send the phase reference optical pulse is performed polarization and time feedback at the Alice end, and the detection result of the time period in which the Bob end sends the phase reference optical pulse and the Alice end does not send the phase reference optical pulse is performed polarization and time feedback at the Bob end.

[0010] Furthermore, the coding period consists of time periods t1, t2, t3, and t4; Alice encodes high-intensity phase reference light pulses in time periods t1 and t3 within the coding period, encodes single-photon level quantum signal light pulses in time period t4, and extinguishes the light in time period t2; Bob encodes high-intensity phase reference light pulses in time periods t2 and t3 within the coding period, encodes single-photon level quantum signal light pulses in time period t4, and extinguishes the light in time period t1.

[0011] Furthermore, the QKD debugging phase includes the following steps:

[0012] Step 1: The detection end sends a clock signal to Alice and Bob, and Alice and Bob perform clock synchronization based on the clock signal;

[0013] Step 2: After clock synchronization is completed, Alice sends a phase reference optical pulse to the detection end, while Bob does not send a phase reference optical pulse. The detection end feeds back the count rates of the first detector and the second detector to Alice. Alice uses the polarization feedback algorithm to adjust the polarization controller to adjust the sum of the count rates of the first detector and the second detector to the maximum value M1.

[0014] Step 3: Alice stops sending phase reference light pulses to the detection end, while Bob sends phase reference light pulses to the detection end. The detection end feeds back the count rates of the first detector and the second detector to Bob. Bob uses the polarization feedback algorithm to adjust the polarization controller to adjust the sum of the count rates of the first detector and the second detector to the maximum value M2.

[0015] Step 4: Alice sends a low-frequency phase reference optical pulse signal to the detection end, and Bob does not send a phase reference optical pulse signal. The detection end accumulates the detection results of the first detector and the second detector according to the frequency of the phase reference optical pulse signal to form a histogram.

[0016] Furthermore, in the step 4, Alice sends a low-frequency phase reference optical pulse signal, and the detection end searches for the rising edge moment of the low-frequency phase reference optical pulse signal sent by Alice according to the histogram, and the rising edge search method is: assuming that the maximum value of the histogram is N, the previous moment value of the rising edge is less than N / 2, and the rising edge moment value is greater than or equal to N / 2;

[0017] Alice stops sending the low-frequency phase reference optical pulse signal, and Bob sends the low-frequency phase reference optical pulse signal to the detection end. The detection end searches for the rising edge time of the low-frequency phase reference optical pulse signal sent by Bob according to the histogram.

[0018] The relative delay of the rising edge of the phase reference optical pulse signal between Alice and Bob is calculated, and Alice and Bob make adjustments based on the relative delay so that the rising edge moments of the low-frequency phase reference optical pulse signals sent from both ends are aligned.

[0019] Furthermore, the QKD debugging stage also includes step five: Alice and Bob use single-ended light emission to send a high-frequency phase reference optical pulse signal, establish a histogram based on the measurement results of the high-frequency phase reference optical pulse signal by the first detector and the second detector, control the rising edge time of the high-frequency phase reference optical pulse signal sent by Alice and Bob to be aligned, and perform precise delay calibration.

[0020] Furthermore, in the QKD operation phase, Alice and Bob send phase reference light pulses and quantum signal light pulses in accordance with the coding period. The detection end counts the count rates of the first detector and the second detector in different time periods of all coding periods within T1 with T1 as the period, and feeds back the count rate of the t1 time period to Alice. When the sum of the count rates is lower than the set value, polarization feedback is performed and fed back to the polarization controller of Alice. Alice uses the polarization feedback algorithm to maintain the sum of the count rates of the t1 time period at a maximum value M1. The detection end feeds back the count rate of the t2 time period to Bob. When the sum of the count rates is lower than the set value, polarization feedback is performed and fed back to the polarization controller of Bob. Bob uses the polarization feedback algorithm to maintain the sum of the count rates of the t2 time period at a maximum value M2.

[0021] Furthermore, the detection end performs statistics with T2 as a period, and accumulates the detection results of the first detector and the second detector in the t1 time period and the t2 time period in each coding period in T2 to form a histogram; the detection end obtains the rising edge time of the light pulse at the Alice end according to the histogram of the t1 time period, and obtains the rising edge time of the light pulse at the Bob end according to the histogram of the t2 time period, calculates the relative delay of the rising edge of the light pulse between the Alice end and the Bob end, and feeds back the relative delay to the sending end to realize time feedback.

[0022] The present invention also proposes a TF-QKD detection end capable of performing polarization and time feedback, which is used to implement the above-mentioned TF-QKD method for performing polarization and time feedback, and the TF-QKD detection end comprises: a polarization module, an optical interference module, a first detector and a second detector; the polarization module is a polarization beam splitter prism or a polarizer;

[0023] The optical fiber from the polarizing module to the transmitting end is a single-mode optical fiber, and the optical fiber from the polarizing module to the first detector and the second detector is a polarization-maintaining optical fiber.

[0024] Furthermore, when the polarizing module is a polarization beam splitter prism, the vertical end outlet of the polarization beam splitter prism is not connected to the detector.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] The present application proposes a TF-QKD method and a detection end that can perform polarization and time feedback. Compared with the detection end of the prior art, the detectors B1 and B2 are removed, that is, the TF-QKD system performs polarization and time feedback based on the detection results of the detectors A1 and A2, which saves costs and reduces system complexity. It also adopts a time-division coding method, which can perform polarization feedback and time feedback according to the detection results of the optical interference module outlet.

[0027] The present application proposes another encoding method, which periodically encodes phase reference light and quantum signal light, wherein a single-ended light emission time period is set in the phase reference light encoding, and Alice / Bob single-ended light emission method is selected within the encoding period, so that the light pulses detected by the detection end within a specific time period all originate from one transmitting end; polarization feedback is performed using the counting rate of the single-ended light emission time period to maximize the counting rate of the single-ended light emission time period, and polarization and time feedback are performed based on the measurement results of the single-ended light emission time period of the phase reference light; detectors A1 and A2 can perform polarization feedback and time feedback through the measurement results of the encoded light pulses.

[0028] During the QKD debugging phase, the single-ended light emission situations are accumulated to form a histogram. The relative delay between Alice and Bob is calculated based on the method of calculating the rising edge time of the histogram, and the delay is calibrated by sending a low-frequency signal at a single end. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0030] Figure 1 An existing TF-QKD transmitter;

[0031] Figure 2 It is a schematic diagram of the arrangement of the detection end device of the present invention;

[0032] Figure 3 The transmitting end device of the present invention is set;

[0033] Figure 4 This is a schematic diagram of the Alice-end optical pulse encoding period of the present invention;

[0034] Figure 5 It is a schematic diagram of the Bob-end optical pulse encoding period of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] In the drawings of the specific embodiments of the present invention, in order to better and more clearly describe the working principles of the various components in the system, the connection relationship of the various parts in the device is shown, which only clearly distinguishes the relative position relationship between the various components, and cannot constitute a limitation on the signal transmission direction, connection sequence and size, dimensions and shape of the components or structures.

[0037] The TF-QKD detection end of the present invention is as follows Figure 2 As shown, it includes: a polarization module, a light interference module BS, a first detector A1, a second detector A2; and Figure 1 Compared with the structure of the detection end in the prior art, the detection end of the present invention removes the detectors B1 and B2. The polarization module can be a polarizer or a polarization beam splitter prism PBS.

[0038] When the polarizing module is a polarization beam splitter prism PBS, the vertical end outlet of the polarization beam splitter prism PBS is not connected to a detector. The optical fiber before the polarizing module is a single-mode optical fiber, and the optical fiber after the polarizing module to the first detector A1 and the second detector A2 is a polarization-maintaining optical fiber.

[0039] The transmitter of the present invention is the same as the existing TF-QKD transmitter capable of performing phase feedback, such as Figure 3 As shown. The light pulse emitted by the light source is modulated by the phase modulator PM, the intensity modulator IM, and the polarization controller PC, and then attenuated by the optical attenuator ATT and sent to the optical fiber link. By setting different intensities and extinction ratios, the phase reference light pulse (high intensity) and the quantum signal light pulse (low intensity, less than the single photon level on average, etc.) can be modulated. The optical fiber link is a single-mode optical fiber. Optionally, the polarization controller PC can also be located at the detection end, before the polarization beam splitter prism PBS at the detection end.

[0040] The transmitting end Alice and Bob periodically encode and send phase reference optical pulses and quantum signal optical pulses. The encoding is encoded in a time division multiplexing manner. The encoding periods of Alice and Bob are as follows: Figure 4 , Figure 5 shown.

[0041] The phase reference optical pulse within the coding period of the present invention includes a time period when Alice's end emits light and Bob's end does not emit light, and a time period when Bob's end emits light and Alice's end does not emit light. The detection result of the time period when Alice's end emits light and Bob's end does not emit light is fed back in polarization and time at Alice's end, and the detection result of the time period when Bob's end emits light and Alice's end does not emit light is fed back in polarization and time at Bob's end.

[0042] The coding period consists of four time periods: t1, t2, t3, and t4. Optionally, an extinction time can be added between t3 and t4 to reduce the impact of detector noise caused by the phase reference light pulse on the detection of the quantum signal light pulse. Alice encodes high-intensity phase reference light pulses in the time periods t1 and t3 of the coding period, encodes single-photon-level quantum signal light pulses in the time period t4, and extinguishes them in the time period t2. Bob encodes high-intensity phase reference light pulses in the time periods t2 and t3 of the coding period, encodes single-photon-level quantum signal light pulses in the time period t4, and extinguishes them in the time period t1. Optionally, the coding period is selected to be 1ms, t1 and t2 are 50ns, t3 is 200ns, and t4 is 700ns.

[0043] During the QKD commissioning phase, follow the steps below to complete the initial adjustment of polarization and delay.

[0044] Step 1: The detection end sends a clock signal to Alice and Bob, and Alice and Bob perform clock synchronization based on the clock signal of the detection end.

[0045] Step 2: After clock synchronization is completed, Alice sends a phase reference light pulse to the detection end, while Bob does not emit light. The detection end feeds back the count rates of the first and second detectors A1 and A2 to Alice. Alice uses the polarization feedback algorithm to adjust the polarization controller PC to adjust the sum of the count rates of the first and second detectors A1 and A2 to the maximum. The maximum sum of the count rates of A1 and A2 at this time is assumed to be M1.

[0046] The polarization feedback algorithm can be used in the following manner, that is, the polarization controller PC is controlled by multiple control quantities, and each control quantity is adjusted in turn until the corresponding count rate reaches the maximum. For example, the polarization controller PC can be a three-paddle polarization controller, and each paddle is adjusted in turn until the corresponding count rate is adjusted to the maximum, and then the next paddle is adjusted until all paddles are adjusted.

[0047] Step 3: After step 2 is completed, Alice stops sending phase reference light pulses to the detection end, while Bob sends phase reference light pulses to the detection end. The detection end feeds back the count rates of the first and second detectors A1 and A2 to Bob, and Bob uses the polarization feedback algorithm to adjust the polarization controller to adjust the sum of the count rates of the first and second detectors A1 and A2 to the maximum. The maximum value of the sum of the count rates of the first and second detectors A1 and A2 at this time is assumed to be M2.

[0048] Step 4: After step 3 is completed, Alice sends a low-frequency phase reference optical pulse signal to the detection end, and Bob does not emit light. The detection end records the detection results and accumulates the detection results of the first and second detectors A1 and A2 according to the frequency of the phase reference optical pulse signal to form a histogram.

[0049] The detection end searches for the rising edge time of the low-frequency phase reference optical pulse signal sent by Alice according to the histogram. The rising edge search method is: let the maximum value of the histogram be N, the value of the previous moment of the rising edge is less than N / 2, and the rising edge moment value is greater than or equal to N / 2.

[0050] Then Alice stops sending the low-frequency phase reference optical pulse signal, and Bob sends the low-frequency phase reference optical pulse signal to the detection end. The detection end records the detection results and accumulates the detection results of the first and second detectors A1 and A2 according to the frequency of the low-frequency phase reference optical pulse signal to form a histogram.

[0051] The detection end searches for the rising edge time of the low-frequency phase reference optical pulse signal sent by the Bob end according to the histogram. The detection end feeds back the rising edge time of the pulses at the Alice end and the Bob end to the Alice end and the Bob end, and the Alice end and the Bob end adjust the delay accordingly, so that the rising edge time of the low-frequency phase reference optical pulse signal sent by the Alice end and the Bob end is aligned.

[0052] Optionally, step 5: After low-frequency calibration, Alice and Bob use single-ended light emission to send high-frequency phase reference optical pulse signals for precise delay calibration. Similar to step 4, a histogram is established based on the measurement results of the high-frequency phase reference optical pulse signals, so that the rising edge moments of the high-frequency phase reference optical pulse signals sent by Alice and Bob are aligned for more precise delay calibration.

[0053] In the QKD operation phase, Alice and Bob send phase reference optical pulses and quantum signal optical pulses according to the coding period. The detection end records the detection results, and counts the count rates of all coding periods in different time periods of the first and second detectors A1 and A2 in T1 with time T1 as the period (optionally, T1 is 1s). The detection end feeds back the count rates of the first and second detectors A1 and A2 in the t1 time period to Alice, and Alice uses the polarization feedback algorithm to maintain the sum of the count rates of A1 and A2 in the t1 time period at M1; the detection end feeds back the count rates of the first and second detectors A1 and A2 in the t2 time period to Bob, and Bob uses the polarization feedback algorithm to maintain the sum of the count rates of the first and second detectors A1 and A2 in the t2 time period at M2, and performs polarization feedback, that is, monitors polarization through the count rate, and starts to perform polarization feedback when the count rate is lower than a certain set value (optionally, 0.95M), and adjusts each control amount of the polarization controller in turn to maximize the count rate.

[0054] The detection end performs statistics with time T2 as a period (optionally, T2 is 1s), and accumulates the detection results of the first and second detectors A1 and A2 in the t1 time period and the t2 time period in each coding cycle within T2. ​​The accumulation method is to divide t1 into several moments based on the clock signal (note that T2 contains multiple coding cycles, each coding cycle contains the t1 time period) and accumulate the number of detection events of the first and second detectors A1 and A2 occurring at each moment, and the accumulation results of all moments in t1 form a histogram; divide t2 into several moments based on the clock signal, and accumulate the number of detection events of the first and second detectors A1 and A2 occurring at each moment, and the accumulation results of all moments in t2 form a histogram. The detection end calculates the rising edge time of the pulse at the Alice end according to the t1 histogram, and calculates the rising edge time of the pulse at the Bob end according to the t2 histogram. Compare the rising edge times of the pulses at the Alice end and the Bob end, and calculate the relative delay of the rising edges of the pulses between Alice and Bob. The detection end or the sending end adjusts the delay based on the relative delay to achieve time feedback. The execution method of time feedback is similar to that of the debugging stage. The relative delay is calculated through the histogram, and then the delay is adjusted accordingly at the sending end or the detection end. For example, the sending end adjusts the pulse sending time.

[0055] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or a data center that includes one or more available media integrated. The available medium may be a magnetic medium, (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid state disk (SSD)), etc.

[0056] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A TF-QKD method capable of performing polarization and time feedback, characterized in that: It includes QKD debugging phase and QKD operation phase; In the QKD debugging stage, the transmitting end sends a phase reference optical pulse to the detecting end, and the detecting end performs initial polarization adjustment and delay adjustment on the phase reference optical pulse; the QKD debugging stage includes the following steps: Step 1: The detection end sends a clock signal to Alice and Bob, and Alice and Bob perform clock synchronization based on the clock signal; Step 2: After clock synchronization is completed, Alice sends a phase reference optical pulse to the detection end, while Bob does not send a phase reference optical pulse. The detection end feeds back the count rates of the first detector and the second detector to Alice. Alice uses the polarization feedback algorithm to adjust the polarization controller to adjust the sum of the count rates of the first detector and the second detector to the maximum value M1. Step 3: Alice stops sending phase reference light pulses to the detection end, while Bob sends phase reference light pulses to the detection end. The detection end feeds back the count rates of the first detector and the second detector to Bob. Bob uses the polarization feedback algorithm to adjust the polarization controller to adjust the sum of the count rates of the first detector and the second detector to the maximum value M2. Step 4: Alice sends a low-frequency phase reference optical pulse signal to the detection end, and Bob does not send a phase reference optical pulse signal. The detection end accumulates the detection results of the first detector and the second detector according to the frequency of the phase reference optical pulse signal to form a histogram. In the QKD operation phase, the transmitting end single-end transmits a phase reference optical pulse and a quantum signal optical pulse with a coding period, the detecting end calculates the relative delay of the transmitting end, realizes the delay calibration of the single-end transmitted optical pulse, and performs polarization feedback based on the detection result of the optical pulse count rate in the single-end transmission time period, so that the single-end transmitted optical pulse count rate reaches a maximum value; The transmitting end includes an Alice end and a Bob end, and the Alice end and the Bob end send phase reference optical pulses and quantum signal optical pulses in accordance with a coding period. The coding period of the phase reference optical pulse includes a time period when Alice sends a phase reference optical pulse and Bob does not send a phase reference optical pulse, and a time period when Bob sends a phase reference optical pulse and Alice does not send a phase reference optical pulse. The detection result of the time period when Alice sends a phase reference optical pulse and Bob does not send a phase reference optical pulse is performed polarization and time feedback at Alice, and the detection result of the time period when Bob sends a phase reference optical pulse and Alice does not send a phase reference optical pulse is performed polarization and time feedback at Bob.

2. The TF-QKD method for performing polarization and time feedback according to claim 1, characterized in that The coding period consists of time periods t1, t2, t3, and t4; Alice encodes high-intensity phase reference light pulses in time periods t1 and t3 within the coding period, encodes single-photon level quantum signal light pulses in time period t4, and extinguishes the light in time period t2; Bob encodes high-intensity phase reference light pulses in time periods t2 and t3 within the coding period, encodes single-photon level quantum signal light pulses in time period t4, and extinguishes the light in time period t1.

3. The TF-QKD method for performing polarization and time feedback according to claim 2, characterized in that In the step 4, Alice sends a low-frequency phase reference optical pulse signal, and the detection end searches for the rising edge moment of the low-frequency phase reference optical pulse signal sent by Alice according to the histogram, and the rising edge search method is: assuming that the maximum value of the histogram is N, the previous moment value of the rising edge is less than N / 2, and the rising edge moment value is greater than or equal to N / 2; Alice stops sending the low-frequency phase reference optical pulse signal, and Bob sends the low-frequency phase reference optical pulse signal to the detection end. The detection end searches for the rising edge time of the low-frequency phase reference optical pulse signal sent by Bob according to the histogram. The relative delay of the rising edge of the phase reference optical pulse signal between Alice and Bob is calculated, and Alice and Bob make adjustments based on the relative delay so that the rising edge moments of the low-frequency phase reference optical pulse signals sent from both ends are aligned.

4. The TF-QKD method for performing polarization and time feedback according to claim 3, characterized in that The QKD debugging stage also includes step five: Alice and Bob use single-ended light emission to send a high-frequency phase reference optical pulse signal, establish a histogram based on the measurement results of the high-frequency phase reference optical pulse signal by the first detector and the second detector, control the rising edge time of the high-frequency phase reference optical pulse signal sent by Alice and Bob to be aligned, and perform precise delay calibration.

5. The TF-QKD method for performing polarization and time feedback according to claim 2, characterized in that: In the QKD operation phase, Alice and Bob send phase reference light pulses and quantum signal light pulses in accordance with the coding period. The detection end counts the count rates of the first detector and the second detector in different time periods of all coding periods within T1 with T1 as the period, and feeds back the count rate of the t1 time period to Alice. When the sum of the count rates is lower than the set value, polarization feedback is performed and fed back to the polarization controller of Alice. Alice uses the polarization feedback algorithm to maintain the sum of the count rates of the t1 time period at a maximum value M1. The detection end feeds back the count rate of the t2 time period to Bob. When the sum of the count rates is lower than the set value, polarization feedback is performed and fed back to the polarization controller of Bob. Bob uses the polarization feedback algorithm to maintain the sum of the count rates of the t2 time period at a maximum value M2.

6. The TF-QKD method for performing polarization and time feedback according to claim 5, characterized in that The detection end performs statistics with T2 as a period, and accumulates the detection results of the first detector and the second detector in the t1 time period and the t2 time period in each coding period in T2 to form a histogram; the detection end obtains the rising edge time of the light pulse at the Alice end according to the histogram of the t1 time period, and obtains the rising edge time of the light pulse at the Bob end according to the histogram of the t2 time period, calculates the relative delay of the rising edge of the light pulse between the Alice end and the Bob end, and feeds back the relative delay to the sending end to realize time feedback.

7. A TF-QKD detector capable of performing polarization and time feedback, used to implement the TF-QKD method for performing polarization and time feedback as described in any one of claims 1 to 6, characterized in that: The TF-QKD detection end includes: a polarization module, an optical interference module, a first detector and a second detector; the polarization module is a polarization beam splitter prism or a polarizer; The optical fiber from the polarizing module to the transmitting end is a single-mode optical fiber, and the optical fiber from the polarizing module to the first detector and the second detector is a polarization-maintaining optical fiber.

8. The TF-QKD detector for performing polarization and time feedback according to claim 7, characterized in that: When the polarizing module is a polarization beam splitter prism, the vertical end outlet of the polarization beam splitter prism is not connected to the detector.

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