QKD system precise delay tracking method and system based on oversampling

Abstract

The invention discloses a QKD system precise delay tracking method and system based on oversampling, and the method specifically comprises the following steps: setting the sampling clock frequency of a detector to be two times of the gating signal frequency, and carrying out the statistics of the distribution of quantum light detection results in two times of sampling in the current operation process of a QKD system, and judging whether the current optical signal has offset or not based on the distribution of the quantum light detection result in the two times of sampling, and if so, adjusting the coding time delay of the sending end or the detection time delay of the receiving end so as to align the quantum optical signal with the gating trigger signal. And the operation of the QKD system does not need to be paused in the tracking process, so that the safety code rate of the system cannot be reduced due to the tracking mechanism, and the high efficiency and the safety of the system are ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum communication. More specifically, the present invention relates to a precise delay tracking method and system for a QKD system based on oversampling. Background Art

[0002] In a quantum key distribution system (QKD), in order to ensure the security and accuracy of data transmission, the gating trigger signal of the receiving end detector needs to be strictly aligned with the quantum optical signal. However, as the system operation time increases, the quantum light will drift, resulting in alignment deviation, which in turn causes problems such as an increase in the bit error rate and a decrease in the key amount.

[0003] In the traditional precise delay tracking method, the system will monitor the number of screened keys after each transmission in real time. Once the fluctuation of the number of screened keys exceeds the set threshold, the system will judge that the optical signal has drifted. At this time, the QKD system will suspend operation and execute a scanning program for detector delay to realign the gating trigger signal of the detector with the quantum optical signal. After the adjustment is completed, the system will resume operation.

[0004] The above delay tracking process occupies a relatively long operation time of the QKD system. During the alignment process of the drifting optical signal, the QKD system needs to be suspended, which to a certain extent reduces the secure coding rate of the QKD system. Summary of the Invention

[0005] The present invention provides a precise delay tracking method for a QKD system based on oversampling, aiming to improve the above problems.

[0006] The present invention is implemented as follows. A precise delay tracking method for a QKD system based on oversampling is as follows:

[0007] Set the sampling clock frequency of the detector to twice the frequency of the gating signal, count the distribution of the quantum optical detection results in two samplings during the current operation of the QKD system, and judge whether there is an offset in the current optical signal based on the distribution of the quantum optical detection results in two samplings. If there is an offset, adjust the encoding delay of the sending end to align the quantum optical signal with the gating trigger signal.

[0008] Further, count the ratio X of the optical quantum detection result of the first sampling and the optical quantum detection result of the second sampling under the detector gating signal during the current operation of the QKD system i , and use the ratio X i to characterize the distribution of the quantum optical detection results in two samplings.

[0009] Further, the detection process of the optical signal offset is as follows:

[0010] Statistically calculate the ratio X of the optical quantum detection result of the first sampling to the optical quantum detection result of the second sampling under the detector gating signal in the current run of the QKD system i , and calculate the ratio X i and the deviation value ΔX 0 from the standard ratio X i = |X i - X 0 |. If the deviation value ΔX i is greater than or equal to the deviation threshold θ, it is determined that the current optical signal has drift;

[0011] The standard ratio X 0 is the distribution ratio of the optical quantum signal detection results in the two samplings when there is no optical signal offset in the QKD system.

[0012] Furthermore, the configuration process of the standard ratio X 0 is specifically as follows:

[0013] When the QKD system is started, control the QKD system to run m times, and statistically calculate the ratio odd of the optical quantum detection result N even of the first sampling to the optical quantum detection result N of the second sampling under the detector gating signal in each run of the QKD system Take the average ratio of the m ratios X 0 as the standard ratio X

[0014] Furthermore, the adjustment process of the encoding delay at the sending end is specifically as follows:

[0015] Determine the adjustment direction of the encoding delay;

[0016] Based on the determined encoding delay direction, adjust the encoding delay so that the ratio X i of the optical quantum detection result of the first sampling to the optical quantum detection result of the second sampling under the detector gating signal during the operation of the QKD system

[0017] is within the deviation threshold θ from the standard ratio.

[0018] Furthermore, the determination process of the adjustment direction of the encoding delay is specifically as follows: When it is detected that the deviation value ΔX i is greater than or equal to the deviation threshold θ, control the encoding delay at the sending end to adjust in the set direction;

[0019] Based on the ratio X i+1 of the optical quantum detection result of the first sampling to the optical quantum detection result of the second sampling under the detector gating signal in the next run of the QKD systemDetermine whether the current encoding delay adjustment direction is correct. If it is correct, use the set direction as the adjustment direction of the current encoding delay. If it is incorrect, take the reverse of the set direction as the adjustment direction of the current encoding delay.

[0020] Further, count the ratio X of the optical quantum detection result of the first sampling to the optical quantum detection result of the second sampling under the detector gating signal in the (i + 1)-th run of the QKD system i+1 , calculate the ratio X i+1 and the standard ratio X 0 to obtain the deviation value ΔX i+1 = |X i+1 - X 0 |. If the deviation value ΔX i+1 is greater than the deviation value ΔX i , then the currently set encoding delay adjustment direction is incorrect. If the deviation value ΔX i+1 is less than the deviation value ΔX i , then the currently set encoding delay adjustment direction is correct.

[0021] Further, the encoding delay adjustment process based on determining the encoding delay direction is as follows;

[0022] Real-time detect whether there is an optical signal offset in the current run of the QKD system. If there is, adjust the encoding delay by the delay step d in the adjustment direction.

[0023] The present invention is implemented as follows. An oversampling-based QKD system fine delay tracking system, the system comprising:

[0024] A sending end and a detector, and a processor communicatively connected to the sending end and the detector;

[0025] Set the sampling clock frequency of the detector to twice the gating signal frequency. The detector counts the distribution of the quantum optical detection results in two samplings during the current run of the QKD system and sends it to the processor. The processor adjusts the encoding delay of the sending end based on the above-mentioned oversampling-based QKD system fine delay tracking method to align the quantum optical signal with the gating trigger signal.

[0026] The oversampling-based QKD system fine delay tracking method provided by the present invention has the following beneficial technical effects: (1) The configuration process takes less than 1 ms, has a minimal impact on the normal operation of the system, and ensures the fast response ability of the system; (2) High-precision tracking: It can sensitively identify and correct small deviations during the tracking process, thus ensuring the stable operation of the system and the accuracy of data transmission; (3) High secure key generation rate: During the tracking process, there is no need to pause the operation of the QKD system, so the secure key generation rate of the system will not be reduced due to the tracking mechanism itself, ensuring the high efficiency and security of the system. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the fine delay tracking system of the QKD system based on oversampling provided by the embodiment of the present invention;

[0028] Figure 2 It is a flowchart of the fine delay tracking method of the QKD system based on oversampling provided by the embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the sampling principle of oversampling provided by the embodiment of the present invention. Embodiment

[0031] The following will further describe the specific embodiments of the present invention in detail with reference to the drawings and through the description of the embodiments, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0032] Figure 1 It is a schematic structural diagram of the fine delay tracking system of the QKD system based on oversampling provided by the embodiment of the present invention. For the sake of convenience of description, only the parts related to the embodiment of the present invention are shown. The system includes:

[0033] A sending end and a receiving end, and a host computer communicatively connected to the sending end and the receiving end;

[0034] Set the sampling clock frequency of the detector at the receiving end to twice the frequency of the gating signal, perform two samplings within one gating signal period, count the distribution of the quantum light detection results in the two samplings during the current operation of the QKD system, and judge whether the current optical signal has an offset based on the distribution of the quantum light detection results in the two samplings. If not, there is no need to adjust the encoding delay of the sending end. If there is, adjust the encoding delay of the sending end or the detection delay of the detector at the receiving end to align the quantum optical signal with the gating trigger signal. In addition, Figure 3 A schematic diagram of the principle of oversampling is given.

[0035] Figure 2 It is a flowchart of the fine delay tracking method of the QKD system based on oversampling provided by the embodiment of the present invention. The method is as follows:

[0036] Set the sampling clock frequency of the detector to twice the frequency of the gating signal, count the distribution of the quantum light detection results in the two samplings during the current operation of the QKD system, and judge whether the current optical signal has an offset based on the distribution of the quantum light detection results in the two samplings. If there is, adjust the encoding delay of the sending end or the detection delay of the detector at the receiving end to align the quantum optical signal with the gating trigger signal.

[0037] (1) The detection process of the optical signal offset is as follows:

[0038] Configuration process: Since there is basically no optical signal offset at the initial stage of the QKD system startup, when the QKD system starts, control the QKD system to run m times, and count the distribution of the quantum optical detection results in two samplings during each run of the QKD system, that is, the optical quantum detection result N in the first sampling under the detector gating signal odd and the optical quantum detection result N in the second sampling even ratio Obtain m ratios X, and take the average ratio of the m ratios X as the true distribution of the quantum optical signal detection results in the first sampling and the second sampling. Set the deviation threshold θ of the ratio and the adjustment delay step d of the laser coding, and take the average ratio as the standard ratio X 0 ;

[0039] Count the ratio X of the optical quantum detection result in the first sampling and the optical quantum detection result in the second sampling under the detector gating signal during the current run of the QKD system i , calculate the ratio X i and the deviation value ΔX of the standard ratio X 0 =|X i -X i |. If the deviation value ΔX 0 is less than the deviation threshold θ, it is determined that the current optical signal has no drift. On the contrary, if the deviation value ΔX i is greater than or equal to the deviation threshold θ, it is determined that the current optical signal has drift, and then it is necessary to adjust the coding delay of the sending end or the detection delay of the receiving end detector to align the quantum optical signal with the gating trigger signal i .

[0040] (2) The correction process for the drifting optical signal can be to correct the coding delay of the sending end or the detection delay of the receiving end detector to align the quantum optical signal with the gating trigger signal. The correction method for the coding delay of the sending end is the same as the correction method for the detection delay of the receiving end. The following takes the coding delay of the sending end as an example for explanation. The coding delay of the sending end mainly includes: determining the adjustment direction of the coding delay and adjusting the coding delay based on the determined coding delay direction so that the ratio X i of the optical quantum detection result in the first sampling and the optical quantum detection result in the second sampling under the detector gating signal during the operation of the QKD system and the difference of the standard ratio are within the deviation threshold θ

[0041] (21) The process of determining the adjustment direction of the coding delay of the sending end is specifically as follows:

[0042] (211) When detecting the deviation value ΔX iWhen it is greater than or equal to the deviation threshold θ, control the encoding delay of the sending end to be adjusted in the set direction;

[0043] (212) Based on the ratio X of the optical quantum detection result of the first sampling and the optical quantum detection result of the second sampling under the detector gating signal in the next run of the QKD system i+1 Determine whether the current encoding delay adjustment direction is correct. If it is correct, use the set direction as the adjustment direction of the current encoding delay. If it is incorrect, take the reverse of the set direction as the adjustment direction of the current encoding delay.

[0044] In the embodiment of the present invention, taking the adjustment of the encoding delay in the positive increasing direction as an example, the determination process of the adjustment direction of the encoding delay of the sending end is described as follows:

[0045] When the detected deviation value ΔX i is greater than or equal to the deviation threshold θ, control the encoding delay of the sending end to increase the delay step d on the basis of the current delay D 0 , D 1 = D 0 + d;

[0046] Statistically analyze the ratio X of the optical quantum detection result of the first sampling and the optical quantum detection result of the second sampling under the detector gating signal in the (i + 1)-th run of the QKD system i+1 , calculate the deviation value ΔX of the ratio X i+1 and the standard ratio X 0 , ΔX i+1 = |X i+1 - X 0 |. If the deviation value ΔX i+1 is greater than the deviation value ΔX i , it means that the currently set encoding delay adjustment direction is incorrect. Adjust the encoding delay adjustment direction of the sending end to decrease the delay step d on the basis of the current delay D 1 . In order to quickly align the quantum optical signal and the gating trigger signal, adjust the encoding delay adjustment direction of the sending end to decrease the delay step 2d on the basis of the current delay D 1 , D 2 = D 1 - 2d. If the deviation value ΔX i+1 is less than the deviation value ΔX i , it means that the currently set encoding delay adjustment direction is correct.

[0047] (22) Adjust the encoding delay based on the determined encoding delay direction;

[0048] Real-time detect whether there is an optical signal offset in the current operation of the QKD system. If there is, adjust the coding delay by the delay step d in the adjustment direction. As the coding delay is continuously adjusted, the ratio X in the current operation of the QKD system i+1 and the standard ratio X 0 have a smaller and smaller deviation. Eventually, the deviation between the ratio X i+1 and the standard ratio X 0 will be within the deviation threshold θ. At this time, it is necessary to adjust the coding delay of the sending end again.

[0049] The present invention has been described by way of example. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A QKD system precise delay tracking method based on oversampling, characterized in that: The method is specifically as follows: The sampling clock frequency of the detector is set to twice the frequency of the gating signal, and the distribution of the quantum light detection results in the two samplings during the current operation of the QKD system is counted. Based on the distribution of the quantum light detection results in the two samplings, it is determined whether the current optical signal has an offset. If so, the coding delay of the transmitter or the detection delay of the receiver is adjusted to align the quantum light signal with the gating trigger signal.

2. The QKD system precise delay tracking method based on oversampling as claimed in claim 1, characterized in that: Count the ratio of the first sampled photon detection result to the second sampled photon detection result under the detector gating signal in the current operation of the QKD system X i , using the ratio X i Characterize the distribution of quantum light detection results in two samplings.

3. The QKD system precise delay tracking method based on oversampling as claimed in claim 2, characterized in that: The optical signal deviation detection process is as follows: Count the ratio of the first sampled photon detection result to the second sampled photon detection result under the detector gating signal in the current operation of the QKD system X i , calculate the ratio X i Deviation ΔX from the standard ratio X0 i =|X i -X0|, if the deviation value ΔX i If it is greater than or equal to the deviation threshold θ, it is considered that the current optical signal has drift; The standard ratio X0 is the distribution ratio of the quantum light signal detection results in the second sampling when there is no light signal offset in the QKD system.

4. The QKD system precise delay tracking method based on oversampling as claimed in claim 3, characterized in that: The configuration process of the standard ratio X0 is as follows: When the QKD system is started, the QKD system is controlled to run m times, and the light quantum detection results N of the first sampling under the detector gating signal of the QKD system during each operation are counted. odd The photon detection result N of the second sampling even Ratio The average ratio of m ratios X As the standard ratio X0.

5. The QKD system precise delay tracking method based on oversampling as claimed in claim 1, characterized in that: The adjustment process of the encoding delay at the transmitter is as follows: Determine the adjustment direction of the coding delay; The coding delay is adjusted based on the determined coding delay direction so that the ratio of the first sampled photon detection result to the second sampled photon detection result under the detector gating signal in the QKD system during operation is X i The difference from the standard ratio is within the deviation threshold θ.

6. The QKD system precise delay tracking method based on oversampling as claimed in claim 5, characterized in that: The process of determining the adjustment direction of the coding delay is as follows: When the deviation value ΔX is detected i When it is greater than or equal to the deviation threshold θ, the coding delay of the transmitter is controlled to be adjusted in the set direction; The ratio X of the photon detection result of the first sampling to the photon detection result of the second sampling under the detector gating signal in the next operation of the QKD system is i+1 Determine whether the current coding delay adjustment direction is correct. If correct, take the set direction as the current coding delay adjustment direction. If incorrect, take the reverse direction of the set direction as the current coding delay adjustment direction.

7. The QKD system precise delay tracking method based on oversampling as claimed in claim 6, characterized in that: Statistical value X of the ratio of the first sampled photon detection result to the second sampled photon detection result under the detector gating signal in the i+1th operation of the QKD system i+1 , calculate the ratio X i+1 Deviation ΔX from the standard ratio X0 i+1 =|X i+1 -X0|, if the deviation value ΔX i+1 Greater than the deviation value ΔX i , then the current setting of the coding delay adjustment direction is incorrect. If the deviation value ΔX i+1 Less than the deviation value ΔX i , the current encoding delay adjustment direction is correct.

8. The QKD system precise delay tracking method based on oversampling as claimed in claim 5, characterized in that: The coding delay adjustment process based on determining the coding delay direction is as follows; It is detected in real time whether there is an optical signal offset in the current operation of the QKD system. If so, the coding delay is adjusted in the adjustment direction by adjusting the delay step d.

9. A QKD system precision delay tracking system based on oversampling, characterized in that: The system comprises: The transmitter and receiver of the QKD system, and the host computer connected to the transmitter and receiver; The sampling clock frequency of the detector at the receiving end is set to twice the frequency of the gating signal. The detector counts the distribution of the quantum light detection results of the QKD system in two samplings during the current operation and sends it to the processor. The host computer adjusts the coding delay of the transmitting end or the detection delay of the receiving end based on the QKD system precision delay tracking method based on oversampling as described in any one of claims 1 to 8 to align the quantum light signal with the gating trigger signal.

Images