A method and system for determining a delay value of a gate signal based on interval approximation

Abstract

The application provides a delay value determination method and system of a gating signal based on interval approximation. Without changing the existing system hardware and firmware interface, the application determines the delay position of the gating signal corresponding to the maximum detection count through interval distribution and gradual cyclic approximation of each interval, effectively reduces the time for single-photon detection position calibration, and improves the speed and performance of a quantum key distribution system.

Description

Technical Field

[0001] This invention belongs to the field of single-photon detection technology, specifically relating to a method and system for determining the delay value of a gated signal based on interval approximation. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] The initialization phase and operation monitoring process of a quantum key distribution system require calibration of the detection position of the single-photon detector to optimize detection efficiency. The key is to determine the optimal value of the delay of the gating signal so that the detection count of photons collected at that point is maximized.

[0004] According to the inventor, the current common approach involves iterating through the delayed signal's delay chip settings according to the smallest adjustable step size, until the maximum adjustable delay value of the delayed chip is reached. The delay value corresponding to the maximum detection count is then confirmed as the optimal calibration value. Since the minimum step size is determined by the hardware circuit design and the selection of the delayed chip, and this process is time-consuming, it results in long waiting times for device response and slow response speeds during initialization / operation monitoring, impacting efficiency. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method and system for determining the delay value of a gated signal based on interval approximation. Without altering the existing system hardware and firmware interface, this invention determines the gated signal delay position corresponding to the maximum detector count by partitioning and progressively cyclically approximating each interval, effectively reducing the calibration time for single-photon detector positions and thus improving the speed and performance of the quantum key distribution system.

[0006] According to some embodiments, the present invention adopts the following technical solution:

[0007] A method for determining the delay value of a gated signal based on interval approximation includes the following steps:

[0008] Set two gate delay values ​​within the range of the gate signal delay value, and divide the entire range into three continuous intervals;

[0009] Determine if there is background noise in the middle interval. If so, discard the middle interval and take the current rightmost interval as the starting interval. Extend the current delay value range by using the length of the current delay value range as the update length to form a new delay value range.

[0010] If not, determine the detection count corresponding to the delay values ​​of the two gate signals, and based on the determination result, discard the leftmost or rightmost interval to form a new delay value range;

[0011] The delay values ​​of the two gating signals are reset, and the updated range is divided into three consecutive intervals. The above judgment and update process is repeated until the latest gating signal delay value range can no longer be divided. The delay value at this time is the optimal value, thus realizing the calibration of the single photon detection position.

[0012] As an alternative implementation, the delay value of the gating signal is an integer.

[0013] As an alternative implementation, the size difference between each of the three intervals is less than a set value.

[0014] As an alternative implementation method, the specific process of determining whether there is background noise in the interval includes: if the detection count corresponding to the delay values ​​of the two gate signals is less than the set threshold, it is considered that there is background noise in the middle interval. The rightmost interval is taken as the new starting interval, and the interval is extended to the right by mid1+T lengths to form a new delay value range. The mid1 is the end point value of the leftmost interval in the previous cycle, and the T is the length of the initial delay value range.

[0015] As an alternative implementation method, the specific process of determining the detection count corresponding to the delay values ​​of the two gating signals and discarding the leftmost or rightmost interval based on the determination result includes:

[0016] If the detection counts n1 and n2 corresponding to the delay values ​​mid1 and mid2 of the two gating signals are such that if n1 is less than n2, the current leftmost interval is discarded and the updated delay value range is [mid1, right]; if n1 is greater than n2, the rightmost interval is discarded and the updated delay value range is [left, mid2], where [left, right] is the delay value range of the previous cycle before the update.

[0017] As an alternative implementation, if the delay value t of the gate signal exceeds the range of [0, A] during the process of sending it to the quantum key distribution system, then the actual detection count obtained by sending it to the quantum key distribution system is equivalent to the detection count obtained when the delay value is tA, where A is the length of the delay value range in the current cycle.

[0018] As an alternative implementation, if background noise still exists in the interval during the repeated judgment and update process, a fault is reported and the calibration process fails.

[0019] As an alternative implementation, the steps of the method are performed when the quantum key distribution system is started or when the quantum key distribution system malfunctions.

[0020] A system for determining the delay value of a gated signal based on interval approximation, comprising:

[0021] The interval division module is configured to set the delay values ​​of two gate signals within the delay value range of the gate signal, dividing the entire range into three continuous intervals;

[0022] The background noise removal module is configured to determine whether there is background noise in the middle interval. If so, the middle interval is discarded, and the rightmost interval is taken as the starting interval. The current delay value range is extended sequentially with the length of the current delay value range as the update length to form a new delay value range.

[0023] The iterative update module is configured to, if not, determine the detection count corresponding to the delay values ​​of the two gating signals, discard the leftmost or rightmost interval based on the determination result, form a new delay value range, reset the delay values ​​of the two gating signals, divide the updated range into three consecutive intervals, and repeat the above determination and update process until the latest gating signal delay value range can no longer be divided. The delay value at this point is the optimal value, thereby achieving the calibration of the single-photon detection position.

[0024] An electronic device includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the steps in the method described above.

[0025] A computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the steps in the above method.

[0026] A quantum key distribution system, wherein the receiver is a gated detector, and the delay value of the gated signal is determined by the above method or includes the above system.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention is applicable to quantum key distribution systems with gated detectors at the receiver. It can be implemented without modifying the hardware, only through firmware upgrades, without increasing hardware costs. Furthermore, the firmware upgrade reuses the previous communication interface, without affecting the original system, making the upgrade simple.

[0029] Based on the characteristics of the curve, an interval approximation method is provided, which can quickly calibrate the single-photon detection position, reduce the startup time of the quantum key distribution system, improve the network response time of the quantum key distribution system, reduce the single-photon detection position calibration time during anomaly handling, and thus improve the key generation rate.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] Figure 1 This is a flowchart illustrating the process of this embodiment;

[0033] Figure 2 This is a schematic diagram illustrating the update of the delay value range in the background noise region of this embodiment;

[0034] Figure 3 This is a schematic diagram illustrating the update of the delay value range when the detection count n1 is greater than n2 in this embodiment;

[0035] Figure 4 This is a schematic diagram illustrating the update of the delay value range when the detection count n1 is less than n2 in this embodiment;

[0036] Figure 5 This is a schematic diagram of the quantum key distribution system in this embodiment;

[0037] Figure 6 This is a schematic diagram of the scan gating signal delay value-detection count curve in this embodiment. Detailed implementation method:

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] This invention provides a method for determining the delay value of a gated signal based on interval approximation. By setting the delay values ​​of two gated signals, the delay value interval of the gated signal is divided into three roughly equal parts. The magnitudes of the detection counts corresponding to these two delay values ​​are compared, thereby narrowing the interval of the gated signal delay value scan. This process is repeated until the delay value scan interval cannot be further divided, thereby finding the peak point of the gated signal delay value-detection count curve, thus completing the single-photon detection position calibration.

[0042] Specifically, a typical embodiment will be used for description:

[0043] like Figure 1 As shown, a method for determining the delay value of a gated signal based on interval approximation is executed when the quantum key distribution system starts up and when an anomaly occurs in the quantum key distribution system. The method includes the following steps:

[0044] (1) Calculate the delay values ​​(mid1, mid2) of the two gating signals. Divide the range of delay values ​​[left, right] of the detector gating signals into three intervals [left, mid1), [mid1, mid2), [mid2, right]. The length of each interval (step_length) is approximately 1 / 3 of the entire delay value range right-left, i.e., A (the initial delay value range right-left = T).

[0045] The delay values ​​mid1 and mid2 of the gating signal must be integers.

[0046] In some embodiments, the sizes of the three intervals may be inconsistent. However, having them relatively similar can help save iteration execution time and simplify the entire process.

[0047] Similarly, in some embodiments, the three intervals can also be [left, mid1], (mid1, mid2], (mid2, right], or [left, mid1], (mid1, mid2), [mid2, right], or (left, mid1], (mid1, mid2], (mid2, right). That is, there is no strict restriction on which interval the endpoints belong to.

[0048] (2) Send the delay values ​​mid1 and mid2 to the system respectively to obtain the corresponding detection counts n1 and n2.

[0049] (3) Compare the values ​​of n1 and n2.

[0050] If n1 < N and n2 < N, the starting endpoint of the left interval is changed to mid2, and the starting endpoint of the right interval is changed to mid1+T. This discards the intervals with background noise (i.e., the middle intervals), forming a new [left, right] (or [left', right']). Figure 2 As shown;

[0051] To overcome the influence of the detector's background noise, a threshold N is set, which is usually about 2 to 3 times the dark count of the detector.

[0052] Otherwise: if the value of n1 is larger, the endpoint of the right interval is changed to mid2 (i.e., the rightmost interval is discarded), such as... Figure 3 As shown, [left, mid2] at this point is used as the new [left, right] for the next cycle; otherwise, the starting endpoint of the left interval is changed to mid1 (discarding the leftmost interval), and [mid1, right] at this point is used as the new [left, right] for the next cycle, as follows. Figure 4 As shown.

[0053] (4) For the updated [left, right] or [left', right'] (because the updated range has been replaced and updated, but is still the range of gated signal delay values), calculate the delay values ​​(mid1', mid2') of the two new gated signals, and divide the updated range of detector gated signal delay values ​​(left, right) into three intervals, each interval length (step_length) is about 1 / 3 of the entire delay value range right-left.

[0054] Similarly, there are no strict restrictions on whether the updated left and right are within the interval or which interval they belong to. Therefore, some places above use (left, right) and some use [left, right], which is only for illustration. The partitioning standard can be unified by oneself.

[0055] (5) The delay values ​​mid1' and mid2' of the new gating signals are sent to the system respectively, such as Figure 3 , Figure 4 As shown, the corresponding detection counts n1' and n2' are obtained.

[0056] (6) Compare the numerical values ​​of n1' and n2'.

[0057] If n1' < N and n2' < N, then a gated single-photon detector fault is reported, and the calibration process fails.

[0058] Otherwise: if the value of n1' is larger, the end point of the right interval is changed to mid2' (i.e., the rightmost interval is discarded), and [left', mid2'] at this time is the new [left, right] for the next cycle. The start point of the left interval is changed to mid1' (the leftmost interval is discarded), and [mid1', right'] at this time is the new [left, right] for the next cycle.

[0059] The above process ensures that the length of the entire delay value range is reduced and updated in each loop.

[0060] (7) Repeat steps (4) to (6) above until the range of the gate signal delay value cannot be further divided (or reduced). At this point, the delay value is the optimal value (i.e., the peak point of the gate signal delay value-detection count curve), thus completing the calibration of the single photon detection position.

[0061] If the delay value t in each of the above cycles exceeds the range of [0-A] in the current cycle during the transmission process, then the actual transmission of the detector count is equivalent to the transmission of the detector count with the delay value tA.

[0062] The above method is applicable to all quantum key distribution (QKD) systems where the receiver is a gated detector, such as... Figure 5 As shown. The structure of the gated detector can use the existing structure. Using the above method, the phase shifter in the delay module of the gated detector is calibrated to adjust the delay position of the gated signal, quickly finding the optimal gated signal delay position that matches the input optical pulse signal.

[0063] The entire quantum key distribution system controls the transmitter to generate a delayed scanning test light, and the receiver automatically adjusts the delay position of the control gate signal by detecting the detection count of the gated single-photon detector, so that the detection count of the gated single-photon detector reaches the maximum and locks the delay position of the gate signal corresponding to the maximum detection count.

[0064] This invention provides an interval approximation method based on the characteristics of the curve, which can quickly calibrate the single-photon detector position, reduce the startup time of the QKD system, improve the response time of the QKD network, reduce the single-photon detector position calibration time during anomaly handling, and thus improve the code generation rate.

[0065] The curve represents the gate signal delay value versus the detector count curve, such as... Figure 6 As shown, this figure is for illustrative purposes only; the specific detection count and delay value ranges will be determined based on the specific design. Due to the presence of dark counts from the detector, there will be some noise at the bottom of the curve, such as... Figure 6 As shown, at the position of delay value 33, there is a small peak on the curve of the detection count caused by background noise. This invention improves the accuracy and efficiency and enhances the performance of the quantum key distribution system by judging whether there is an interval with background noise, i.e., the first part in step (3).

[0066] Quantum key distribution systems utilizing the above methods should also be within the scope of protection of this invention.

[0067] The present invention also provides the following product examples:

[0068] A system for determining the delay value of a gated signal based on interval approximation, comprising:

[0069] The interval division module is configured to set the delay values ​​of two gate signals within the delay value range of the gate signal, dividing the entire range into three continuous intervals;

[0070] The background noise removal module is configured to determine whether there is background noise in the middle interval. If so, the middle interval is discarded, and the current rightmost interval is taken as the starting interval. The delay value range is used as the update length to form a new delay value range.

[0071] The iterative update module is configured to, if not, determine the detection count corresponding to the delay values ​​of the two gating signals, discard the leftmost or rightmost interval based on the determination result, form a new delay value range, reset the delay values ​​of the two gating signals, divide the updated range into three consecutive intervals, and repeat the determination and update process until the latest gating signal delay value range can no longer be divided. The delay value at this point is the optimal value, thereby achieving calibration of the single-photon detection position.

[0072] An electronic device includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the steps in the method described above.

[0073] A computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the steps in the above method.

[0074] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0075] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0076] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0077] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0078] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for determining the delay value of a gated signal based on interval approximation, characterized in that: Includes the following steps: Set two gate delay values ​​within the range of the gate signal delay value, and divide the entire range into three continuous intervals; Determine if there is background noise in the middle interval. If so, discard the middle interval and take the current rightmost interval as the starting interval. Extend the current delay value range by using the length of the current delay value range as the update length to form a new delay value range. If not, determine the probe count corresponding to the delay values ​​of the two gating signals. Based on the determination result, discard the leftmost or rightmost interval to form a new delay value range. The specific process includes: if the probe counts corresponding to the delay values ​​mid1 and mid2 of the two gating signals are n1 and n2, if n1 is less than n2, discard the current leftmost interval and use [mid1, right] as the updated delay value range; if n1 is greater than n2, discard the rightmost interval and use [left, mid2] as the updated delay value range, where [left, right] is the delay value range of the previous cycle before the update. The delay values ​​of the two gating signals are reset, and the updated range is divided into three consecutive intervals. The above judgment and update process is repeated until the latest gating signal delay value range can no longer be divided. The delay value at this time is the optimal value, thus realizing the calibration of the single photon detection position.

2. The method for determining the delay value of a gated signal based on interval approximation as described in claim 1, characterized in that: The delay value of the gating signal is an integer.

3. The method for determining the delay value of a gated signal based on interval approximation as described in claim 1, characterized in that: The difference in size between the three intervals is less than a set value.

4. The method for determining the delay value of a gated signal based on interval approximation as described in claim 1, characterized in that: The specific process for determining whether there is background noise in an interval includes: if the detection count corresponding to the delay values ​​of the two gated signals is less than the set threshold, then it is considered that there is background noise in the middle interval. The rightmost interval is taken as the new starting interval, and the interval is extended to the right by mid1+T lengths to form a new delay value range. The mid1 is the end point value of the leftmost interval in the previous cycle, and T is the length of the initial delay value range.

5. The method for determining the delay value of a gated signal based on interval approximation as described in claim 1, characterized in that: If the delay value t of the gate signal exceeds the range of [0, A] during the process of sending it to the quantum key distribution system, then the actual probe count obtained by sending it to the quantum key distribution system is equal to the probe count obtained when the delay value is tA, where A is the length of the delay value range in the current cycle.

6. A method for determining the delay value of a gating signal based on interval approximation as described in any one of claims 1-5, characterized in that: If background noise still exists in the interval during the repeated judgment and update process, a fault is reported and the calibration process fails.

7. A method for determining the delay value of a gating signal based on interval approximation as described in any one of claims 1-5, characterized in that: Each step is executed when the quantum key distribution system starts up or when the quantum key distribution system malfunctions.

8. A system for determining the delay value of a gated signal based on interval approximation, characterized in that: include: The interval division module is configured to set the delay values ​​of two gate signals within the delay value range of the gate signal, dividing the entire range into three continuous intervals; The background noise removal module is configured to determine whether there is background noise in the middle interval. If so, the middle interval is discarded, and the rightmost interval is taken as the starting interval. The current delay value range is extended sequentially with the length of the current delay value range as the update length to form a new delay value range. The iterative update module is configured to, if not, determine the detection count size corresponding to the delay values ​​of the two gating signals. Based on the determination result, discard the leftmost or rightmost interval to form a new delay value range. The specific process includes: if the detection count sizes n1 and n2 corresponding to the delay values ​​mid1 and mid2 of the two gating signals are, if n1 is less than n2, discard the current leftmost interval and use [mid1, right] as the updated delay value range; if n1 is greater than n2, discard the rightmost interval and use [left, mid2] as the updated delay value range, where [left, right] is the delay value range of the previous cycle before the update; reset the delay values ​​of the two gating signals, divide the updated range into three consecutive intervals, and repeat the above determination and update process until the latest gating signal delay value range can no longer be divided. The delay value at this point is the optimal value, realizing the calibration of the single-photon detection position.

9. An electronic device, characterized in that: It includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, which, when executed by the processor, perform the steps of the method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the steps of the method according to any one of claims 1-7.

11. A quantum key distribution system, characterized in that: The receiving end is a gated detector, which uses the steps of the method described in any one of claims 1-7 to determine the delay value of the gated signal or includes the system described in claim 8.

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