阅读说明：本技术 一种用于量子密钥生成系统的实时位同步修正方法 (Real-time bit synchronization correction method for quantum key generation system ) 是由 张立华 李镇 于 2019-01-31 设计创作，主要内容包括：本申请提供一种用于量子密钥生成系统的实时位同步修正方法,主要步骤包括：①位同步处理单元持续读取探测器实时计数值及其对应的实时延时值,获取探测器探测延时效率关系、探测器最大单位时间计数值和其对应的最佳延时值；②判断是否启动实时位同步反馈流程；③位同步处理单元获取探测器当前计数和探测器当前延时值,得到下一次扫描的延时值,并发送给延时控制单元；④调整将探测器的延时值；⑤探测器进行计数累计；⑥位同步处理单元判断是否进行下一步⑦修正探测器的延时值；⑧延时控制单元调整探测器延时值为最佳延时值,完成本轮位同步修正,回到①；本方法无需中断系统的密钥生成流程,提高了密钥产生速率和系统的鲁棒性。(The application provides a real-time bit synchronization correction method for a quantum key generation system, which mainly comprises the steps that an ① bit synchronization processing unit continuously reads a detector real-time count value and a corresponding real-time delay value thereof to obtain a detector detection delay efficiency relation, a detector maximum unit time count value and a corresponding optimal delay value thereof, ② judges whether a real-time bit synchronization feedback process is started or not, a ③ bit synchronization processing unit obtains the current count of the detector and the current delay value of the detector to obtain a delay value of next scanning and sends the delay value to a delay control unit, ④ adjusts the delay value of the detector, ⑤ detector counts and accumulates, a ⑥ bit synchronization processing unit judges whether to correct the delay value of the detector by ⑦, a ⑧ delay control unit adjusts the delay value of the detector to be the optimal delay value to complete the round of bit synchronization correction and return to ①, the key generation process of the system does not need to be interrupted, and the key generation rate and the robustness of the system are improved.)

1. A real-time bit synchronization correction method for a quantum key generation system is characterized in that:

firstly, a bit synchronization processing unit continuously reads a real-time counting value of a detector and a real-time delay value of the corresponding detector, and obtains a delay efficiency relation of the detector, a maximum counting value of unit time and an optimal delay value of the maximum counting value of unit time;

secondly, judging whether a real-time bit synchronization feedback process is started or not according to the parameters obtained in the first step, returning to the first step if the real-time bit synchronization feedback process is judged to be not started, and executing the next step if the real-time bit synchronization feedback process is judged to be started;

thirdly, the bit synchronization unit acquires the current count of the detector and the current delay value of the detector, and then acquires the delay value of the next scanning according to the delay efficiency relationship;

fourthly, the delay control unit adjusts the delay value of the detector to the delay value obtained by the third step bit synchronization unit;

fifthly, counting and/or corresponding accumulated time by the detector according to the delay value set in the fourth step;

sixthly, judging whether the current delay value of the detector is the optimal delay value of the detector or not by the bit synchronization processing unit according to the count and/or the corresponding accumulated time obtained in the fifth step; if the current delay value is the optimal delay value, returning to the first step after the wheel bit synchronous correction process is finished; if the current delay value is not the optimal delay value, the next step is carried out;

seventhly, correcting the current delay value of the detector into the optimal delay value of the detector by bit synchronization processing, and sending the optimal delay value to a delay control unit;

and step eight, the delay control unit adjusts the delay value of the detector to the optimal delay value obtained in the step seven, and returns to the step one after the current round of synchronous correction is completed.

2. The real-time bit synchronization correction method for a quantum key generation system according to claim 1, wherein: the unit time in the first step, including,

setting a certain fixed time when the current wheel position synchronous correction is started or before the start;

or a commonly used basic unit of time.

3. The real-time bit synchronization correction method for a quantum key generation system according to claim 1, wherein:

the delay efficiency relationship in the first step is a pre-calibrated discrete point-to-point relationship, or a pre-calibrated functional relationship obtained according to a discrete point-to-point relationship, or a discrete point-to-point relationship obtained in real time or by machine learning or the like or a functional relationship obtained according to a discrete point-to-point relationship when in actual use.

4. The real-time bit synchronization correction method for a quantum key generation system according to claim 1, wherein: the real-time counting value of the detector in the first step includes a real-time detection counting value or an accumulated counting value obtained according to the real-time detection counting in unit time.

5. The real-time bit synchronization correction method for a quantum key generation system according to claim 1, wherein: the maximum count value of the detector in unit time in the first step is obtained by comparing the real-time count value of the current detector in unit time with the currently recorded maximum count value of the unit time;

if the current real-time count value of the detector is greater than the currently recorded maximum count value of the detector in unit time, updating the currently recorded maximum count value of the detector in unit time into the current real-time count value of the detector in unit time; if the real-time count value of the current detector in unit time is less than or equal to the maximum count value of the current recorded detector in unit time, keeping the maximum count value of the current recorded detector in unit time unchanged;

or if the real-time unit time counting value of the current detector is greater than or equal to the maximum unit time counting value of the current recorded detector, updating the maximum unit time counting value of the current recorded detector into the real-time unit time counting value of the current detector; and if the real-time unit time count value of the current detector is smaller than the maximum unit time count value of the current recorded detector, keeping the maximum unit time count value of the current recorded detector unchanged.

6. The real-time bit synchronization correction method for a quantum key generation system according to claim 1, wherein: judging whether to start a real-time bit synchronization feedback process according to the parameters acquired in the first step, wherein the step of judging whether the real-time unit time count value of the current detector is lower than a set threshold value; if the real-time unit time count value of the current detector is lower than the set threshold, the judgment result is yes, otherwise, the judgment result is no; the set threshold is a set value, and the threshold is smaller than the maximum count value of the detector in unit time.

7. The real-time bit synchronization correction method for a quantum key generation system according to claim 1, wherein: the third step of obtaining the delay value of the next scan comprises: the bit synchronization processing unit obtains two possible delay values corresponding to the current real-time unit time count of the detector in the delay efficiency relationship by searching the delay efficiency relationship, wherein the delay value larger than the detection efficiency peak value is called a forward delay value, and the other delay value is called a backward delay value; the bit synchronization processing unit obtains a difference value between the forward delay value and the backward delay value; then the bit synchronization processing unit adds or subtracts a value smaller than the difference value to the current delay value of the detector, and the obtained result or the obtained result is used as the delay value of the next scanning of the detector after the obtained result or the obtained result is modulus to the pulse period and is sent to the delay control unit; and simultaneously, the bit synchronization processing unit records the difference value of the delay values corresponding to the two possible delay values and the peak value of the delay efficiency relation.

8. The method of claim 2, wherein the running total comprises: counting and accumulating by the detector according to the delay value set in the fourth step, wherein the counting and accumulating by the detector are carried out according to the delay value set in the fourth step and counting and accumulating time;

the counting accumulated time is set time or time in a basic unit;

or the count accumulation time is configured by the recipient.

9. The real-time bit synchronization modification method for a quantum key generation system according to claim 7, wherein: and the sixth step of judging whether the current delay value of the detector is the optimal delay value of the detector or not, including,

the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and the current unit time count is more than or equal to the unit time count obtained by the current count and/or the corresponding accumulated time in the third step;

adding a certain value smaller than the difference to the current delay value of the detector, and when the certain value smaller than the difference is equal to the difference of the delay values corresponding to the peak values of the relationship between the backward delay value and the delay efficiency, judging that the current delay value of the detector is the optimal delay value, or, subtracting the certain value smaller than the difference from the current delay value of the detector, and when the certain value smaller than the difference is equal to the difference of the delay values corresponding to the peak values of the relationship between the forward delay value and the delay efficiency, judging that the current delay value of the detector is the optimal delay value;

otherwise, the judgment is no.

10. The real-time bit synchronization modification method for a quantum key generation system according to claim 7, wherein: and the current delay value of the detector in the seventh step is corrected to the optimal delay value of the detector, including,

if the current delay value of the detector is added with a value smaller than the difference value, the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and when the current count and/or the unit time count obtained in the corresponding accumulated time in the third step are larger than or equal to the unit time count obtained in the third step, the delay value of the detector is corrected to be: thirdly, the current delay value is the backward delay value, and the delay value obtained by adding the difference value of the backward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value;

if the current delay value of the detector is added with a value smaller than the difference value, the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and when the current delay value of the detector is smaller than the unit time count obtained by the current count and/or the corresponding accumulated time in the third step, the delay value of the detector is corrected to be: thirdly, the current delay value is the forward delay value, and the delay value obtained by subtracting the difference value of the forward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value;

if the current delay value of the detector subtracts a value smaller than the difference, the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and the current unit time count is greater than or equal to the unit time count obtained by the current count and/or the corresponding accumulated time in the third step, the delay value of the detector is corrected to be: thirdly, the current delay value is the forward delay value, and the delay value obtained by subtracting the difference value of the forward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value;

if the current delay value of the detector subtracts a value smaller than the difference, the bit synchronization processing unit obtains the current unit time count from the count obtained in the fifth step and/or the corresponding accumulated time, and the current unit time count is smaller than the unit time count obtained from the current count and/or the corresponding accumulated time in the third step, the delay value of the detector is corrected to be: and thirdly, the current delay value is the backward delay value, and the delay value obtained by adding the difference value of the backward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value.

Technical Field

The application relates to the field of quantum communication, in particular to a real-time bit synchronization correction method for a quantum key generation system.

Background

Since the twenty-first century, with the overall popularization of the internet, the global informatization level is continuously improved, the attention of governments, national defense, enterprises and individuals to information security is increasingly enhanced, and the demand for information security is increasing day by day. Meanwhile, the information security faces more and more serious threats, particularly in the Shor algorithm based on the quantum computer proposed in 1994, the subversion breaks the foundation of the classical cryptography protocol based on the computational complexity.

In recent years, Quantum Key Distribution (QKD) technology has attracted much attention because its unconditional security is guaranteed by the fundamental principles of Quantum mechanics. Many international research institutes have conducted intensive research on theory and application, and some companies have also successively introduced commercial quantum key distribution products.

In a quantum key distribution system, a transmitting end encodes a quantum signal (photon) and then transmits the encoded quantum signal to a receiving end through a quantum channel. Commonly used quantum channels include optical fibers and free space (i.e., the atmosphere). The receiving end needs to confirm the arrival time of the photon in order to use the detector to detect at the right moment, which is the bit synchronization process. After the bit synchronization process is completed, the quantum key distribution system can perform a subsequent negotiation process to generate a security key.

The inventor finds in the course of research of the present application that the optimum instant for detection by the detector varies over time. This is because the transmission time of photons in the quantum channel is usually affected by the environment, and especially when the ambient temperature changes, the length and refractive index of the quantum channel also change. When the photon transmission time changes, the optimal time for the detector to detect changes. The detection at the 'optimal detection moment' before the change can reduce the effective detection efficiency of the detector, the detection count is reduced, and the generation rate of the safe password of the quantum key distribution system is also obviously reduced or even can not normally operate.

The quantum channel based on optical fiber is taken as an example and explained as follows: with the change of the environmental temperature, the length and the refractive index of the optical fiber are changed, and the change amount Δ t of the transmission time of the photon is calculated as follows:

in the formula, n_effIs a refractive index, L_effΔ temp. is the temperature change, α is the linear expansion coefficient, and ξ is the temperature coefficient of refractive index for the fiber length.

For fused silica fiber, the linear expansion coefficient α is 5.5 × 10^-7V. C, temperature coefficient of refractive index ξ ═ n_eff×0.68×10^-5/° c, then calculated according to the above equation: the change in photon transit time per kilometer of fiber is about 30ps per degree celsius change in temperature. Then the variation of photon transmission time can reach 30000ps at most for a quantum key distribution system with the quantum channel length of 100km running in the beijing area. (according to the forecast result of the weather of the China weather bureau 2018, 10 months and 18 days: cloudy, 13-23 ℃ and 3-4 grades of east wind.)

In order to ensure stable operation of the quantum key generation system, the optimal time for the detector to detect needs to be adjusted according to changes of the external environment during the working process of the quantum key generation system, which is called a bit synchronization correction process. A common bit synchronization correction scheme is an interrupted bit synchronization correction scheme. Besides, the influence of the external environment on the quantum key generation system can be reduced through a wavelength optimization scheme.

The existing solution of interrupt-type bit synchronization correction is that when the count of a detector is obviously reduced (for example, the current count of the detector is less than 50% of the maximum count of the detector), the overall signal-to-noise ratio of the system is obviously reduced, the bit error rate is obviously improved, at this time, the quantum key generation system cannot normally work, the key generation process of the quantum key generation system needs to be stopped, the bit synchronization process is started, and the key generation process of the quantum key generation system is restarted after the bit synchronization process is completed.

Another modification scheme for optimizing the wavelength of the synchronous light is that the synchronization between the quantum key generation systems is realized by using a synchronous light mode, and in order to reduce the influence of the environment on the photon transmission time, the wavelength difference between the synchronous light wavelength and the quantum signal light wavelength is selected to be as small as possible.

However, during the research process of the present application, the inventors found that the interrupted feedback scheme is inefficient, and will reduce the effective operation time of the quantum key generation system. Particularly, with the acceleration of the change of the external environment temperature and the increase of the length of the quantum channel, the change rate of the photon transmission time is increased, the starting frequency of the interrupted feedback scheme is increased, and the stable operation of the quantum key generation system is seriously influenced.

The solution of optimizing the wavelength of the synchronous light is only to reduce the influence of environmental changes on the optimal detection time of the detector, but when the environmental changes are further aggravated or the length of the quantum channel is further increased, the problem that the optimal time for the detector to detect changes with the influence of the environmental temperature still exists. Meanwhile, the scheme is limited by the existing wavelength division multiplexing technology, when the wavelength difference between the synchronous light and the quantum signal light is small, the influence of the synchronous light on the quantum signal light is not negligible, and the introduced noise reduces the performance of the quantum key generation system.

Disclosure of Invention

The application provides a real-time bit synchronization method for a quantum key generation system, which aims to solve the problem that in the prior art, the detection count of a receiving end of the quantum key generation system is reduced due to the change of an external environment, so that the generation rate of a security key is reduced. The method can monitor the detection count in real time, and when the detection count is reduced due to the change of the photon transmission time, the method starts a real-time bit synchronization correction process to obtain the optimal detection time without interrupting the safety key generation process of the quantum key generation system.

The method sets a proper detector counting minimum threshold relative to the maximum counting of the detector, and judges whether the counting of the detector exceeds the threshold in real time according to the minimum threshold, so as to judge whether the optimal moment for the detector to detect changes.

The lowest count threshold, which is typically set, is relatively close to the maximum count, and the change in the optimum detection instant of the detector is relatively small when the event occurs that the current detector count value exceeds the set lowest threshold, meaning that a search can be made within a relatively small range around the current delay value to find the optimum detection instant (i.e., without having to search through the entire pulse range). Within a small range near the current delay value, the count value of the detector is not obviously reduced, and although the working performance of the quantum key generation system is slightly reduced, the security key can be normally generated without interrupting the key generation process.

The method comprises the following steps: a real-time bit synchronization correction method for a quantum key generation system,

firstly, a bit synchronization processing unit continuously reads a real-time counting value of a detector and a real-time delay value of the corresponding detector, and obtains a delay efficiency relation of the detector, a maximum counting value of unit time and an optimal delay value of the maximum counting value of unit time;

secondly, judging whether a real-time bit synchronization feedback process is started or not according to the parameters obtained in the first step, returning to the first step if the real-time bit synchronization feedback process is judged to be not started, and executing the next step if the real-time bit synchronization feedback process is judged to be started;

thirdly, the bit synchronization unit acquires the current count of the detector and the current delay value of the detector, and then acquires the delay value of the next scanning according to the delay efficiency relationship;

fourthly, the delay control unit adjusts the delay value of the detector to the delay value obtained by the third step bit synchronization unit;

fifthly, counting and/or corresponding accumulated time by the detector according to the delay value set in the fourth step;

sixthly, judging whether the current delay value of the detector is the optimal delay value of the detector or not by the bit synchronization processing unit according to the count and/or the corresponding accumulated time obtained in the fifth step; if the current delay value is the optimal delay value, returning to the first step after the wheel bit synchronous correction process is finished; if the current delay value is not the optimal delay value, the next step is carried out;

seventhly, correcting the current delay value of the detector into the optimal delay value of the detector by bit synchronization processing, and sending the optimal delay value to a delay control unit;

and step eight, the delay control unit adjusts the delay value of the detector to the optimal delay value obtained in the step seven, and returns to the step one after the current round of synchronous correction is completed.

Preferably, said unit of time in the first step, including,

setting a certain fixed time when the current wheel position synchronous correction is started or before the start;

or a commonly used basic unit of time.

Preferably, the delay efficiency relationship in the first step is a pre-calibrated discrete point-to-point relationship, or a pre-calibrated functional relationship obtained according to a discrete point-to-point relationship, or a discrete point-to-point relationship obtained in real time or by machine learning or a functional relationship obtained according to a discrete point-to-point relationship when in actual use.

Preferably, the real-time counting value of the detector in the first step includes a real-time detection counting value or an accumulated counting value obtained from the real-time detection counting value in a unit time.

Preferably, the maximum count value of the detector in unit time obtained in the first step is obtained by comparing the current real-time count value of the detector with the currently recorded maximum count value of the detector in unit time;

if the current real-time count value of the detector is greater than the currently recorded maximum count value of the detector in unit time, updating the currently recorded maximum count value of the detector in unit time into the current real-time count value of the detector in unit time; if the real-time count value of the current detector in unit time is less than or equal to the maximum count value of the current recorded detector in unit time, keeping the maximum count value of the current recorded detector in unit time unchanged;

or if the real-time unit time counting value of the current detector is greater than or equal to the maximum unit time counting value of the current recorded detector, updating the maximum unit time counting value of the current recorded detector into the real-time unit time counting value of the current detector; and if the real-time unit time count value of the current detector is smaller than the maximum unit time count value of the current recorded detector, keeping the maximum unit time count value of the current recorded detector unchanged.

Preferably, the step of judging whether to start the real-time bit synchronization feedback process according to the parameters obtained in the first step includes judging whether a count value of a current detector in real time per unit time is lower than a set threshold; if the real-time unit time count value of the current detector is lower than the set threshold, the judgment result is yes, otherwise, the judgment result is no; the set threshold is a set value, and the threshold is smaller than the maximum count value of the detector in unit time.

Preferably, the obtaining the delay value of the next scan in the third step comprises: the bit synchronization processing unit obtains two possible delay values corresponding to the current real-time unit time count of the detector in the delay efficiency relationship by searching the delay efficiency relationship, wherein the delay value larger than the detection efficiency peak value is called a forward delay value, and the other delay value is called a backward delay value; the bit synchronization processing unit obtains a difference value between the forward delay value and the backward delay value; then the bit synchronization processing unit adds or subtracts a value smaller than the difference value to the current delay value of the detector, and the obtained result or the obtained result is used as the delay value of the next scanning of the detector after the obtained result or the obtained result is modulus to the pulse period and is sent to the delay control unit; and simultaneously, the bit synchronization processing unit records the difference value of the delay values corresponding to the two possible delay values and the peak value of the delay efficiency relation.

Preferably, the detector performs count accumulation according to the delay value set in the fourth step, including that the detector performs count accumulation according to the count accumulation time according to the delay value set in the fourth step;

the counting accumulated time is set time or time in a basic unit;

or the count accumulation time is configured by the recipient.

Preferably, said sixth step of determining whether the current delay value of the detector is the optimal delay value of the detector includes,

the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and the current unit time count is more than or equal to the unit time count obtained by the current count and/or the corresponding accumulated time in the third step;

adding a certain value smaller than the difference to the current delay value of the detector, and when the certain value smaller than the difference is equal to the difference of the delay values corresponding to the peak values of the relationship between the backward delay value and the delay efficiency, judging that the current delay value of the detector is the optimal delay value, or, subtracting the certain value smaller than the difference from the current delay value of the detector, and when the certain value smaller than the difference is equal to the difference of the delay values corresponding to the peak values of the relationship between the forward delay value and the delay efficiency, judging that the current delay value of the detector is the optimal delay value;

otherwise, the judgment is no.

Preferably, the current delay value of the probe in the seventh step is corrected to the optimal delay value of the probe, including,

if the current delay value of the detector is added with a value smaller than the difference value, the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and when the current count and/or the unit time count obtained in the corresponding accumulated time in the third step are larger than or equal to the unit time count obtained in the third step, the delay value of the detector is corrected to be: thirdly, the current delay value is the backward delay value, and the delay value obtained by adding the difference value of the backward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value;

if the current delay value of the detector is added with a value smaller than the difference value, the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and when the current delay value of the detector is smaller than the unit time count obtained by the current count and/or the corresponding accumulated time in the third step, the delay value of the detector is corrected to be: thirdly, the current delay value is the forward delay value, and the delay value obtained by subtracting the difference value of the forward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value;

if the current delay value of the detector subtracts a value smaller than the difference, the bit synchronization processing unit obtains the current unit time count according to the count obtained in the fifth step and/or the corresponding accumulated time, and the current unit time count is greater than or equal to the unit time count obtained by the current count and/or the corresponding accumulated time in the third step, the delay value of the detector is corrected to be: thirdly, the current delay value is the forward delay value, and the delay value obtained by subtracting the difference value of the forward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value;

if the current delay value of the detector subtracts a value smaller than the difference, the bit synchronization processing unit obtains the current unit time count from the count obtained in the fifth step and/or the corresponding accumulated time, and the current unit time count is smaller than the unit time count obtained from the current count and/or the corresponding accumulated time in the third step, the delay value of the detector is corrected to be: and thirdly, the current delay value is the backward delay value, and the delay value obtained by adding the difference value of the backward delay value and the delay value corresponding to the peak value of the delay efficiency relationship is the optimal delay value.

The scheme has the following advantages:

1. the method comprises the steps of counting the detectors in real time, counting the counts of the detectors, judging according to the change of the counts of the detectors, and starting a real-time bit synchronization correction process to obtain the optimal detection time when the detection counts are reduced due to the change of photon transmission time without interrupting the safety key generation process of the quantum key generation system.

2. The detector counting accumulation time is not fixed, the self-adaptive adjustment of the quantum channel is realized according to the detector counting, and when the detector counting value per second is higher, the detector counting accumulation time is correspondingly shortened, which is beneficial to improving the efficiency of a real-time bit synchronization scheme.

3. And judging to obtain a deviation value between the current detection time and the optimal detection time according to the relation between the detection efficiency and the time of the detector and the reduction ratio of the effective detection count, thereby directly calculating to obtain the optimal detection time.

The method monitors the counting of the detector in real time and then carries out statistics. And judging whether bit synchronization is needed according to the change of the counting of the detector. When the detection count is reduced due to the change of the photon transmission time, the method starts a real-time bit synchronization correction process to obtain the optimal detection time without interrupting the safety key generation process of the quantum key generation system.

According to the scheme provided by the application, when the counting of the detector is reduced, the key generation process of the quantum key generation system does not need to be stopped, and feedback is carried out in real time, so that the effective working time of the quantum key distribution system is prolonged, and the safe key generation rate of the quantum key distribution system is improved.

Meanwhile, the scheme also reduces the influence of the external environment on the quantum key distribution system through the feedback mode, and improves the robustness of the quantum key distribution system.

Drawings

In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow diagram of a high-speed bit synchronization correction method of a quantum key generation system according to the present application;

fig. 2 is a relationship between effective detection efficiency and detection time of the detector.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description.

The method utilizes a plurality of detectors to simultaneously measure local delay values, and integrates a plurality of local delay value measurement results to obtain an optimal delay value, thereby achieving the purpose of reducing the time for establishing bit synchronization. The work flow of the whole method is shown in fig. 1, and the main steps comprise:

firstly, a bit synchronization processing unit continuously reads a real-time counting value of a detector and a real-time delay value of the corresponding detector, and obtains a delay efficiency relation of the detector, a maximum counting value of unit time and an optimal delay value of the maximum counting value of unit time;

secondly, judging whether a real-time bit synchronization feedback process is started or not according to the parameters obtained in the first step, returning to the first step if the real-time bit synchronization feedback process is judged to be not started, and executing the next step if the real-time bit synchronization feedback process is judged to be started;

thirdly, the bit synchronization unit acquires the current count of the detector and the current delay value of the detector, and then acquires the delay value of the next scanning according to the delay efficiency relationship;

fourthly, the delay control unit adjusts the delay value of the detector to the delay value obtained by the third step bit synchronization unit;

fifthly, counting and/or corresponding accumulated time by the detector according to the delay value set in the fourth step;

sixthly, judging whether the current delay value of the detector is the optimal delay value of the detector or not by the bit synchronization processing unit according to the count and/or the corresponding accumulated time obtained in the fifth step; if the current delay value is the optimal delay value, returning to the first step after the wheel bit synchronous correction process is finished; if the current delay value is not the optimal delay value, the next step is carried out;

seventhly, correcting the current delay value of the detector into the optimal delay value of the detector by bit synchronization processing, and sending the optimal delay value to a delay control unit;

and step eight, the delay control unit adjusts the delay value of the detector to the optimal delay value obtained in the step seven, and returns to the step one after the current round of synchronous correction is completed.

The method carries out statistics by obtaining the detector count in real time, judges according to the change of the detector count, and starts a real-time bit synchronization correction process to obtain the optimal detection time when the detection count is reduced due to the change of the photon transmission time without interrupting the safety key generation process of the quantum key generation system.

In the method, the counting accumulated time of the detector is not fixed, the self-adaptive adjustment of the quantum channel is realized according to the counting of the detector, and when the counting value of the detector per second is higher, the counting accumulated time of the detector is correspondingly shortened, which is beneficial to improving the efficiency of a real-time bit synchronization scheme.

According to the method, the deviation value between the current detection time and the optimal detection time is judged and obtained according to the relation between the detection efficiency and the time of the detector and the reduction ratio of the effective detection count, and therefore the optimal detection time is obtained through direct calculation.

The method monitors the counting of the detector in real time and then carries out statistics. And judging whether bit synchronization is needed according to the change of the counting of the detector. When the detection count is reduced due to the change of the photon transmission time, the method starts a real-time bit synchronization correction process to obtain the optimal detection time without interrupting the safety key generation process of the quantum key generation system.

According to the scheme provided by the application, when the counting of the detector is reduced (for example, the counting of the current detector is less than 95% of the maximum counting of the detector, as shown in figure 2), the key generation process of the quantum key generation system is not required to be stopped, and feedback is carried out in real time, so that the effective working time of the quantum key distribution system is prolonged, and the safe key generation rate of the quantum key distribution system is improved.

Meanwhile, the scheme also reduces the influence of the external environment on the quantum key distribution system through the feedback mode, and improves the robustness of the quantum key distribution system.

[ example 1 ]

Step 101, the bit synchronization processing unit continuously reads the real-time count values of the detectors and the corresponding real-time delay values thereof, and obtains the relationship of the detection delay efficiency of the detectors, the maximum count value of the unit time of the detectors and the corresponding optimal delay value thereof.

The unit time counting value is the counting in a certain time period with a certain length set at the starting time or before the starting of the current rotation synchronous correction, the unit time is a fixed time period set in advance, the unit time counting value can be determined by counting accumulation and/or the accumulated time of the counting, the counting accumulation time can be obtained in three ways, ① a reasonable and random time period temporarily designated by a detector at the counting time, ② a commonly used basic time unit such as second, millisecond or picosecond is adopted, ③ the counting value is calculated according to the detector counting value of the unit time set by the detector at the starting time or before the starting of the current rotation synchronous correction and the counting value of the current real-time unit time of the detector.

The third acquisition mode comprises the following specific processes:

setting proper effective accumulated counts of the detectors for each detector, calculating the accumulated time of the counts of the detectors according to the effective accumulated counts, counting the counts of the detectors according to the accumulated time, and simultaneously recording and updating the maximum value det _ cnt of the counts of each detector in unit time_max。

The detector count accumulated time T is determined according to the detector count value current _ det _ cnt of the current unit time, and the specific method is as follows:

when current _ det _ cnt is less than N₁One/second, the effective accumulated time T of the detector counting is set as T₁；

Current _ det _ cnt is greater than N₂One/second, the effective accumulated time T of the detector counting is set as T₂；

Current _ det _ cnt is not less than N₁One/second, and current _ det _ cnt is not greater than N₂The number per second, the effective accumulated time T counted by the detector is set;

n is above₀、N₁、N₂、T₁、T₂The appropriate value can be set according to the needs of the user.

The maximum value of the obtained detector count is obtained by comparing the detector count value of the current detector in real time unit time with the maximum detector count value of the current recorded unit time;

if the current real-time count value of the detector is greater than the currently recorded maximum count value of the detector in unit time, updating the currently recorded maximum count value of the detector in unit time into the current real-time count value of the detector in unit time; if the real-time count value of the current detector in unit time is less than or equal to the maximum count value of the current recorded detector in unit time, keeping the maximum count value of the current recorded detector in unit time unchanged;

or if the real-time unit time counting value of the current detector is greater than or equal to the maximum unit time counting value of the current recorded detector, updating the maximum unit time counting value of the current recorded detector into the real-time unit time counting value of the current detector; and if the real-time unit time count value of the current detector is smaller than the maximum unit time count value of the current recorded detector, keeping the maximum unit time count value of the current recorded detector unchanged.

The delay efficiency relationship in this step may be calibrated when the instrument leaves a factory, or may be obtained by machine learning and other methods when the detector works.

And 102, judging whether the delay value of the corresponding detector is at the optimal detection time or not according to the counting value of the current detector in unit time and the set lowest threshold value of the detector counting in unit time. And if the event that the counting value of the current detector in unit time is less than the set lowest counting threshold value in unit time appears for one time or multiple times continuously, starting a real-time bit synchronization feedback process. The method calls the delay value of the detector as the initial delay value of the detector and records the initial delay value as t_c。

103, according to the current count det _ cnt of the detector_cAnd the current det _ cnt_maxBy passingObtaining the position of the count in relation to the delay efficiency of the detector, and setting thisThe time detector counts in units of time cnt₀This value is recorded by the bit sync processing unit.

Because the delay efficiency relationship of the detector has a peak value, the delay value corresponding to the current count has two possible positions in the delay efficiency relationship of the detector, that is, the existence of the real-time count corresponds to the two possible delay values in the delay efficiency relationship. Setting the difference between the smaller delay value and the delay value corresponding to the peak value of the delay efficiency relation of the detector as Range₁The difference between the delay value corresponding to the peak value of the relationship between the larger delay value and the delay efficiency of the detector is Range₂The difference between these two possible delay values is Range₁+Range₂

Order to

≤ΔT_Change<Range

Wherein a parameter is divisible in the time domain to ensure the detector count. The delay value required for the subsequent probe is one of two values:

when in useWhen t is₁＝t_c-ΔT_Change。

When in useWhen t is₂＝t_c+ΔT_Change。

Bit synchronization unit will t₁And t₂One of the two values is sent to a delay control unit.

Step 104, the delay control unit adjusts the delay value of the detector to corresponding t according to the delay value sent from step 103₁Or t₂。

Step 105, the bit synchronization unit obtains the corresponding count cnt of the detector per unit time according to the delay value finally sent in step 103₁Or cnt₂。

Step 106, comparing cnt according to the delay value sent by the bit synchronization unit in step 103₁And cnt₀Or comparing cnt₂And cnt₀Finding out the larger value in the count of the detector unit time, and judging t₁Or t₂Whether it is the optimal delay value. The judgment process is as follows:

when Δ T_Change＝Range₁And step 103 bit sync unit sends t₂If cnt₂≥cnt₀If yes, judging as yes;

when Δ T_Change＝Range₂And step 103 bit sync unit sends t₁If cnt₁≥cnt₀If yes, judging as yes;

otherwise, the judgment is no.

If yes, the delay value of the detector is the optimal detection delay value at this time, no further adjustment is needed, and the process returns to step 101.

If not, the delay value of the detector is not the optimal detection delay value, and the flow of the method enters the next step.

Step 107, according to the seventh step of claim 1, correcting the current delay value of the detector to the optimal delay value of the detector, wherein:

if ① the last delay value sent in step 103 is t₁，②cnt₁<cnt₀The delay value of the detector is then corrected to:

when in useWhen, T_c＝t_c+Range₁。

If ① the last delay value sent in step 103 is t₁，②cnt₁＞cnt₀The delay value of the detector is then corrected to:

when in useWhen, T_c＝t_c-Range₂。

If ① the last delay value sent in step 103 is t₂，②cnt₂<cnt₀The delay value of the detector is then corrected to:

when in useWhen, T_c＝t_c-Range₂。

If ① the last delay value sent in step 103 is t₂，②cnt₂＞cnt₀The delay value of the detector is then corrected to:

when in useWhen, T_c＝t_c+Range₁。

After that, the bit synchronization processing unit takes the corrected delay value as the optimal delay value and sends the optimal delay value to the delay control unit.

In step 108, the delay control unit adjusts the delay values of the detectors according to the delay values sent in step 107 to implement bit synchronization correction, and then returns to step 101. the above detailed description of the present application with reference to the specific implementation and the exemplary embodiment is provided, but these descriptions should not be construed as limiting the present application. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the presently disclosed embodiments and implementations thereof without departing from the spirit and scope of the present disclosure, and these fall within the scope of the present disclosure. The protection scope of this application is subject to the appended claims.