Frequency difference estimation and phase compensation method and asynchronous pairing measurement device independent quantum key distribution system, electronic device and storage medium

Abstract

The application provides a frequency difference estimation and phase compensation method and an asynchronous pairing measurement device-independent quantum key distribution system, an electronic device and a storage medium, and relates to the technical field of quantum key distribution. The method comprises the following steps: in the remaining response event, a set response event is determined, which is not used for Z basis vector response event and the light intensity combination is <signal state|signal state>; the set response event is repeatedly paired to generate a paired event set of [2 times signal state, 2 times signal state]; the paired event set is classified and counted according to the pairing step interval duration, the corresponding relationship between the pairing step interval duration and the phase error rate is established, and the fast Fourier transform is performed to extract the frequency difference information; and the frequency difference information is used for pulse pair completion of the X basis vector response event to complete the frequency difference estimation and the phase compensation. The application uses the protocol itself remaining signal state response event for repeated pairing, realizes high-precision frequency difference extraction and phase compensation, and improves the key coding performance and security under long-distance transmission.

Description

Technical Field

[0001] This application relates to the field of quantum key distribution technology, and more specifically, to a frequency difference estimation and phase compensation method, an asynchronous pairing measurement device-independent quantum key distribution system, electronic device, and storage medium. Background Technology

[0002] Quantum key distribution (QKD) provides information-theoretical security for communications. Among them, two-field quantum key distribution (TF-QKD) exhibits superior performance in long-distance quantum secure communication. By introducing a third-party single-photon interference mechanism, it makes the secure key generation rate linearly related to the square root of the channel attenuation. However, the practical deployment of TF-QKD faces significant technical challenges. The core difficulty lies in accurately tracking the relative phase between optical signals propagating over long distances, especially compensating for phase changes caused by the light source and transmission link.

[0003] Asynchronous pairing (mode pairing) measurement device-independent quantum key distribution (AMDI-QKD) has further advanced the practical application of long-distance QKD. This protocol employs a post-measurement coincidence pairing data processing method, tolerating relative phase drift within a specific time window and theoretically eliminating the need for global phase tracking. Compared to classical measurement device-independent protocols, the AMDI-QKD protocol significantly improves the coincidence response probability and breaks through the linear key rate limit through asynchronous two-photon interference.

[0004] However, in practical systems, the two communicating parties use independent lasers, and the inherent frequency difference and random drift between the light sources can quickly introduce phase errors, leading to a sharp deterioration in the key generation rate. This has become the core bottleneck restricting the practical application of long-distance, high-speed quantum key distribution.

[0005] Existing frequency offset compensation schemes are mainly divided into three categories: Using an ultra-stable reference cavity or molecular absorption spectral lines for frequency stabilization can improve the coherence of the light source, but the system is complex, costly, and has limited wavelength selection. Introducing strong reference light for frequency difference estimation based on time division multiplexing requires increasing the reference light power to ensure detector counting, which will introduce backscattering noise, crowd out quantum channel resources, and require strict control of light intensity ratio; Frequency difference extraction based on decoy state quantum signals suffers from insufficient coincidence counting, poor signal-to-noise ratio, low frequency difference estimation accuracy, and high phase error rate in long-distance transmissions over 200 kilometers.

[0006] Therefore, existing technologies cannot achieve high-precision and high-robust frequency difference estimation and phase compensation under low-cost, low-complexity, and long-distance transmission conditions, making it difficult to meet the requirements of practical measurement device-independent quantum key distribution systems. Summary of the Invention

[0007] To address the problems of low frequency difference estimation accuracy, high phase error rate, high system complexity, and insufficient quantum resource utilization in existing measurement-device-independent quantum key distribution technologies for long-distance transmission scenarios, this application provides a frequency difference estimation and phase compensation method and an asynchronous pairing measurement-device-independent quantum key distribution system. This system eliminates the need for additional reference light and utilizes the protocol's own residual signal state response events for repeated pairing, achieving high-precision frequency difference extraction and phase compensation, reducing system complexity, and improving key generation performance and security in long-distance transmission.

[0008] According to a first aspect of this application, at least one embodiment of this application provides a method for frequency difference estimation and phase compensation for asynchronous paired measurement device-independent quantum key distribution, comprising: receiving quantum signal light pulses transmitted by two communicating parties, wherein the light intensity of the quantum signal light pulses includes a signal state, a decoy state, and a vacuum state; performing polarization modulation and single-photon interference on the quantum signal light pulses transmitted by the two communicating parties to obtain detection response events; filtering the detection response events and discarding response events with light intensity combinations of <signal state|decoy state> and <decoy state|signal state>; performing global nearest neighbor pairing on the remaining response events to determine the response events used for X basis vectors and the response events used for generation. The pulse pairs of Z-basis response events are generated as keys; among the remaining response events, a set response event that was not used in the Z-basis response event and whose light intensity combination is <signal state|signal state> is identified; within a preset maximum pairing duration, the set response events are randomly paired again to generate a pairing event set of [2 times signal state, 2 times signal state]; the pairing event set is classified and statistically analyzed according to the pairing step interval duration, and a correspondence between the pairing step interval duration and the phase bit error rate is established; the correspondence is subjected to a fast Fourier transform to extract frequency difference information; the frequency difference information is used for the pulse pairs of the X-basis response events to complete frequency difference estimation and phase compensation.

[0009] For example, in some embodiments of this application, performing global nearest neighbor pairing on the remaining response events to determine pulse pairs for X-basis response events and Z-basis response events for key generation includes: pairing the remaining response events with the nearest remaining response events; generating pulse pairs when the time interval between the remaining response events and the nearest remaining response events is within the maximum pairing time interval; selecting pulse pairs with a sum of light intensity of [signal state, signal state] as pulse pairs for the Z-basis response events; and selecting pulse pairs with a sum of light intensity of [2x decoy state, 2x decoy state] as pulse pairs for the X-basis response events.

[0010] For example, in some embodiments of this application, the step of classifying and statistically analyzing the paired event set according to the paired step interval duration, establishing a correspondence between the paired step interval duration and the phase bit error rate, and performing a fast Fourier transform on the correspondence to extract frequency difference information includes: The phase difference of the quantum signal light pulses between the two communicating parties in the pairing event set is calculated according to the following formula: 、

[0011] The relative phase difference between the two communicating parties is calculated using the following formula:

[0012] The phase quantity is calculated by taking the modulus of the relative phase difference according to the following formula:

[0013] Select the phase quantity as 0 or The phase quantity is calculated, the corresponding bit value of the corresponding pulse pair is calculated, and the bit value is compared with the preset reference bit value to determine whether the corresponding pulse pair is correct, and a judgment value is obtained; the pairing step interval duration is set, and the first step is calculated based on the pairing step interval duration and the judgment value. k The total number of pulse pairing bits and the total number of error bits within the pairing step interval; according to the... k The phase error rate is calculated based on the total number of pulse pairing bits and the total number of erroneous bits within the pairing step interval; wherein... The phase difference of the quantum signal light pulse of one of the communicating parties. The phase difference of the quantum signal light pulse of the other party in the communication is given by the given statement. One of the communicating parties time, The phase of the quantum signal light pulse at a given moment. The other party in the communication time, The phase of the quantum signal light pulse at a given moment. For [2x signal state, 2x signal state], The relative phase difference between the two communicating parties. The phase quantity, , , K The maximum number of segments, The pairing step interval duration, The preset maximum pairing time, , .

[0014] For example, in some embodiments of this application, the selection of the phase quantity is 0 or The phase quantity is calculated, the corresponding bit value of the pulse pair is calculated, and the bit value is compared with the preset reference bit value to determine whether the corresponding pulse pair is correct, and a judgment value is obtained, including: selecting a phase quantity of 0 or The pulse pair is taken as a valid event; the bit value of the pulse pair corresponding to the valid event is calculated; the bit value is compared with a preset reference bit value; if the bit value is consistent with the preset reference bit value, the valid event is determined to be a correct event, and the judgment value of the pulse pair of the valid event is determined. =0; if the bit value is inconsistent with the preset reference bit value, the valid event is determined to be an error event, and the judgment value of the pulse pair of the valid event is determined. =1.

[0015] For example, in some embodiments of this application, the step of setting the pairing step interval duration and calculating the first step based on the pairing step interval duration and the judgment value is described. k The total number of pulse pairing bits and the total number of error bits within the pairing step interval include: Set the pairing step interval duration Time difference By interval Division; For the k Each pulse pair within the specified pairing step interval is assigned a value:

[0016] Calculate the first according to the following formula. k The total number of pulse pairing bit values ​​within the duration of the pairing step interval:

[0017] The total number of error bits within the kth pairing step interval is calculated using the following formula:

[0018] in, The time difference between two response events in the paired event set. The numerical value for each pulse pair, The total number of bit values ​​for the pulse pairing. The judgment value is... The total number of error bits.

[0019] For example, in some embodiments of this application, the statement according to the first kThe phase error rate is calculated by considering the total number of pulse pairing bits and the total number of erroneous bits within the pairing step interval, including: The phase error rate is calculated using the following formula:

[0020] in, The phase error rate is denoted as .

[0021] For example, in some embodiments of this application, the step of using the frequency difference information for the pulse pair of the X basis response event to complete frequency difference estimation and phase compensation includes: calculating the phase compensation amount based on the frequency difference information; and performing post-processing correction on the phase of the pulse pair of the X basis response event based on the event time difference of the pulse pair and the phase compensation amount.

[0022] According to a second aspect of this application, at least one embodiment of this application provides an asynchronous paired measurement device-independent quantum key distribution system, comprising: a first transmitting end and a second transmitting end, each of the first transmitting end and the second transmitting end comprising: a laser source for outputting laser light; an intensity and phase encoding component for intensity modulation and phase encoding of the laser light to generate quantum signal light pulses with light intensities of signal state, decoy state, and vacuum state; an optical attenuator for attenuating the encoded quantum signal light pulses to the single-photon level before sending them into a transmission channel; a measurement end for performing the frequency difference estimation and phase compensation method as described in any one aspect of the first application, the measurement end comprising: a polarization control component for adjusting the polarization state of the transmitted quantum signal light pulses so that the quantum signal light pulses output by the first transmitting end and the second transmitting end are transmitted with the same polarization state; a beam splitter connected to the polarization control component for causing single-photon interference of the quantum signal light pulses output by the first transmitting end and the second transmitting end; a first detector and a second detector. The system is used to acquire interference results and output detection response events; the processor, connected to the first detector and the second detector, is used to filter the detection response events, discarding response events with light intensity combinations of <signal state|decoy state> and <decoy state|signal state>; perform global nearest neighbor pairing on the remaining response events to determine pulse pairs for X-basis response events and Z-basis response events for key generation; among the remaining response events, determine the set response events that are not used for the Z-basis response events and have light intensity combinations of <signal state|signal state>; within a preset maximum pairing duration, perform arbitrary pairwise repeated pairing on the set response events to generate a pairing event set of [2 times signal state, 2 times signal state]; classify and statistically analyze the pairing event set according to the pairing step interval duration, establish the correspondence between the pairing step interval duration and the phase error rate, perform a fast Fourier transform on the correspondence, and extract frequency difference information; use the frequency difference information for the pulse pairs of the X-basis response events to complete frequency difference estimation and phase compensation.

[0023] According to a third aspect of this application, at least one embodiment of this application provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; and, when the one or more programs are executed by the one or more processors, causing the one or more processors to perform the method as described in any one aspect of the first application.

[0024] According to a fourth aspect of this application, at least one embodiment of this application provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the method as described in any one of the first aspects.

[0025] Through the above exemplary embodiments, the frequency difference estimation and phase compensation method, asynchronous pairing measurement device-independent quantum key distribution system, electronic device, and storage medium provided in this application have at least one of the following beneficial effects: By eliminating the dependence on time-division reference light, there is no need to insert strong reference light into the quantum signal. On the one hand, this eliminates the complex power ratio adjustment steps between the reference light and the signal light, reducing the difficulty of system control and implementation complexity. On the other hand, it avoids the backscattering noise generated by strong reference light during long-distance transmission in optical fibers, reducing the interference of noise on quantum signal detection, thereby improving the detection signal-to-noise ratio and phase decoding accuracy. At the same time, it allows all channel resources to be used for quantum encoded information transmission, ensuring that the system achieves higher coding efficiency and code generation performance.

[0026] By publishing the pairwise repetitive pairing mechanism of quantum signal response events in the signal state, the utilization rate of existing quantum resources is improved, the dynamic frequency difference tolerance range between laser sources is expanded, and a longer effective transmission distance of the system is supported.

[0027] By replacing the light source frequency stabilization and frequency locking mechanisms with frequency difference estimation and phase post-compensation, the high coherence requirements of the laser are significantly reduced. It eliminates the need for complex and expensive light source structures such as ultra-stable reference cavities and molecular absorption spectral stabilization, allowing the use of low-cost, compact, narrow-linewidth lasers. At the same time, it eliminates the need for additional modules such as global phase tracking and phase locking, greatly simplifying the system hardware architecture and control logic, reducing the difficulty of system implementation, deployment costs, and maintenance complexity, making it more suitable for practical application and engineering promotion.

[0028] By introducing zero-padding preprocessing into the phase error rate sequence, the spectral resolution of the Fast Fourier Transform is effectively improved without increasing the amount of original sampled data. This makes the frequency difference characteristic peaks sharper and easier to identify, enabling more accurate extraction of weak frequency difference information and significantly improving the accuracy and stability of frequency difference estimation in long-distance, low-count-rate scenarios.

[0029] This application generates a large amount of effective statistical data based on repeated pairing of high-intensity signal states, which has lower requirements for detection counting and higher noise tolerance. It can be well adapted to single-photon avalanche diodes (APDs) with low detection efficiency, without relying on expensive superconducting nanowire single-photon detectors. In practical engineering scenarios with long distances and low count rates, it can still achieve high-precision frequency difference estimation and phase compensation, significantly improving the practicality, compatibility and engineering deployment capability of asynchronous measurement device-independent quantum key distribution systems.

[0030] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0031] The above and other objects, features, and advantages of this application will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings. The drawings described below are merely some embodiments of this application and are not intended to limit the scope of this application.

[0032] Figure 1 This is a schematic diagram of an asynchronous paired measurement device-independent quantum key distribution system according to an embodiment of this application; Figure 2 This is a flowchart of the frequency difference estimation and phase compensation method according to an embodiment of this application; Figure 3 The key bit mapping diagram for the actual protocol under the X basis vector; Figure 4 This is a comparison diagram of the X-basis phase error rate before and after frequency difference estimation and phase compensation in an embodiment of this application; Figure 5 This diagram illustrates the structure of an electronic device provided in this application. Detailed Implementation

[0033] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0034] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0035] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0036] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0037] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0038] Figure 1 This is a schematic diagram of an asynchronous paired measurement device-independent quantum key distribution system according to an embodiment of this application.

[0039] like Figure 1 As shown, the asynchronous paired measurement device-independent quantum key distribution system includes: a first transmitter, a second transmitter, and a measurement terminal.

[0040] The first transmitter and the second transmitter have the same structure, both including: a laser source, an intensity and phase encoding component, and an optical attenuator.

[0041] According to an example embodiment, the laser source is used to output continuous coherent light.

[0042] For example, the laser source is a narrow linewidth semiconductor laser with a selectable center wavelength in the 1550 nm communication band, a linewidth better than 10 kHz, and an output optical power range of 0-10 mW.

[0043] The output of the laser source is optically coupled to the input of the intensity and phase encoding component. The intensity and phase encoding component is used to pulse-cut and intensity-modulate continuous light, generating quantum signal light pulses of three intensities: signal state... Deceptive attitude Vacuum state , , These represent the intensity of the transmitted signal pulses from User 1 and User 2, respectively. The intensity and phase encoding components are also used to randomly encode the phase of each optical pulse. The output of the intensity and phase encoding components is connected to the input of the optical attenuator.

[0044] An optical attenuator is used to precisely attenuate the encoded optical pulse to the level of a single photon. The output of the optical attenuator is connected to a single-mode fiber transmission channel to send the quantum signal optical pulse to the measurement end.

[0045] The measurement end includes: a polarization control component, a beam splitter, a first detector, a second detector, and a processor (not shown in the figure).

[0046] The polarization control component has its input terminals connected to the transmission channels of the first and second transmitters, respectively, and its output terminal connected to a beam splitter. The polarization control component is used to adjust the polarization state of the arriving quantum signal light pulses, compensating for polarization drift introduced by fiber optic transmission, and ensuring that the quantum signal light pulses output from the first and second transmitters are transmitted with the same polarization state.

[0047] The two inputs of the beam splitter receive two quantum signal light pulses from the polarization control component, respectively, to achieve interference between the two single-photon signals. The interference result is then output to the first detector and the second detector.

[0048] The first and second detectors are used to convert the interfered photon signals into electrical pulse signals and output the detection response event (including a timestamp) to the processor.

[0049] According to some embodiments, the first detector and the second detector include a single-photon avalanche diode (APD) or a superconducting nanowire single-photon detector (SNSPD).

[0050] The processor is electrically connected to the first and second detectors and has a built-in data processing unit for performing tasks such as... Figure 2 The measurement device-independent quantum key distribution method shown includes: detection response event filtering, global nearest neighbor pairing; residual signal state event extraction, arbitrary repeated pairing; phase difference calculation, phase error rate statistics, fast Fourier transform frequency difference extraction; X basis phase compensation, key filtering, error correction, and privacy amplification.

[0051] Figure 2 This is a flowchart of the frequency difference estimation and phase compensation method according to an embodiment of this application.

[0052] The first and second transmitters generate and transmit signal states using a laser source, an intensity and phase encoding component, and an optical attenuator, respectively. μ Deceptive attitude v Three types of quantum signal light pulses: vacuum state 0, vacuum state 0, and pulse intensity satisfying: μ a >v a >o a = 0 μ b >v b > o b = 0. Among them, μFor signal state strength, v To determine the intensity of the deception state, o It is in a vacuum state.

[0053] like Figure 2 As shown, the frequency difference estimation and phase compensation method includes steps S201-S208.

[0054] In step S201, quantum signal light pulses sent by both communicating parties are received.

[0055] The measuring end receives quantum signal light pulses from the first and second transmitting ends via an optical fiber channel. The quantum signal light pulses include light pulses with light intensities in the signal state, decoy state, and vacuum state.

[0056] In step S202, polarization modulation and single-photon interference are performed on the quantum signal light pulses sent by both communicating parties to obtain the detection response event.

[0057] The polarization control component at the measurement end performs real-time polarization adjustment on the two optical pulses to ensure that the two optical signals reach the same polarization state. The adjusted optical signals enter the beam splitter and undergo single-photon interference. The first and second detectors convert the interference results into electrical pulses and output detection response events. Each event includes: an event timestamp. t i ,in, i express i time.

[0058] In step S203, the detection response events are filtered, and response events with light intensity combinations of <signal state|decoy state> and <decoy state|signal state> are discarded.

[0059] The processor filters all detection response events and directly discards events with the following two light intensity combinations: <Signal State|Deceptive State>: < | > = < μ a |v b > <Deceptive State|Signal State>: < | >=< v a |μ b > Only the remaining valid response events are retained for subsequent pairing processes.

[0060] In step S204, global nearest neighbor pairing is performed on the remaining response events to determine the pulse pairs for the X basis response events and the Z basis response events for generating the key.

[0061] Perform global nearest neighbor pairing on the remaining filtered response events: For each response event, find the nearest other response event on the timeline; if the time interval between the two events is less than or equal to the preset maximum pairing time interval... T c If the time interval between the two events is greater than 1, the pairing is successful and the pair is retained as a valid pulse pair; if the time interval between the two events is greater than 1, the pairing is successful and the pair is retained as a valid pulse pair. T c If so, then discard the event.

[0062] Effective pulse pairs are classified according to the sum of their light intensities: , This indicates the pairing time corresponding to a successfully paired pulse pair. , Below, the sum of the light intensities of the quantum signal light pulses selected by the first and second transmitting ends, , ,in, express At time. If the sum of the light intensities of the pulse pairs satisfies [ μ a , μ b If the pulse pair is divided into pulse pairs of Z-basis vector response events, it is used to generate key bits, without disclosing intensity and phase information; if the sum of the light intensities of the pulse pair satisfies [ 2v a , 2v b If the pulse pair is divided into pulse pairs of X basis vector response events, it is used for phase decoding and phase compensation is required.

[0063] In step S205, among the remaining response events, the set response events that were not used for the Z basis response events and whose light intensity combination is <signal state|signal state> are determined.

[0064] After completing the Z-basis and X-basis partitioning, extract the light intensity combinations that were not used to generate the Z-basis key and are < μ a |μ b > That is, both communicating parties send response events in signal state and publish the timestamp, intensity, and phase information of these events as the raw data for frequency difference estimation.

[0065] In step S206, within a preset maximum pairing time, the set response events are randomly paired in pairs to generate a pairing event set of [2 times signal state, 2 times signal state].

[0066] Preset maximum pairing time T max ,exist T max Within the time frame, all remaining publicly available < μ a |μ b >Respond to the event, perform arbitrary pairwise repeated pairings to generate a large number of new pulse pairs: [ 2μ a , 2μ b This allows for the construction of a paired event set for frequency difference analysis.

[0067] Any pairing satisfies: Time difference of pairing events = ; 0＜ ≤T max ; j>i .

[0068] In step S207, the pairing event set is classified and statistically analyzed according to the pairing step interval duration, a correspondence between the pairing step interval duration and the phase bit error rate is established, and a fast Fourier transform is performed on the correspondence to extract the frequency difference information.

[0069] For each group The pairing event executes steps S2071-S2074 sequentially: Step S2071, calculate the first transmitter's... , The phase difference of the quantum signal light pulse at a given moment, at the second transmitting end , Phase difference of the quantum signal light pulse at any given moment: 、

[0070] Step S2072, calculate the relative phase difference between the two communicating parties:

[0071] Step S2073: Take the modulus of the relative phase difference and calculate the phase quantity:

[0072] in, The phase difference of the quantum signal light pulse of one of the communicating parties. The phase difference of the quantum signal light pulse of the other party in the communication. One of the two parties in the communication The phase of the quantum signal light pulse at time j. The other party in the communication The phase of the quantum signal light pulse at time j. The relative phase difference between the two communicating parties. This is a phase quantity.

[0073] Step S2074, select phase quantities that are 0 or The pulse pair corresponding to the phase quantity is taken as a valid event. The corresponding bit value of the pulse pair corresponding to the valid event is calculated, and the bit value is compared with the preset reference bit value to determine whether the bit value is correct.

[0074] like Figure 3 As shown, calculating the corresponding bit value for each pulse pair includes: For valid events, Alice extracts a fixed X basis vector bit value of 0, and Bob determines the relative phase. Extract the corresponding bit value: when When =0, Bob's bit value is 0⊕ ⊕ ;when = At that time, Bob's bit value was 1⊕ ⊕ Where ⊕ represents the XOR operation. , These are the response bits of the detector at the measurement end in the early and late time windows, respectively, and if the first detector D... L The response is recorded as 0, and the second detector D R The response is recorded as 1. Bob's bit value is then corrected based on the actual response events from the detector: if... =0 and both detectors respond, or = If the same detector responds twice, Bob's bit value is flipped; otherwise, the bit value remains unchanged. The corrected Bob bit value is compared with Alice's preset reference bit value (fixed at 0). If they match, the bit value is considered correct; if they do not match, the bit value is considered incorrect. This process completes the bit correctness judgment for valid events, providing a data basis for subsequent phase error rate statistics.

[0075] In the field of quantum key distribution (QKD), Alice and Bob are standard pronouns for two legitimate communication parties in quantum communication, corresponding to the first and second transmitters in the AMDI-QKD system of this application.

[0076] If the bit value matches the preset reference bit value, the valid event is determined as a correct event, and the judgment value of the corresponding pulse pair is determined. = 0; If the bit value is inconsistent with the preset reference bit value, the valid event is determined as an error event, and the judgment value of the corresponding pulse pair is determined. = 1.

[0077] Step S2075: Set the pairing step interval duration, and calculate the first step based on the pairing step interval duration and the judgment value. k The total number of pulse pairing bits and the total number of error bits within a pairing step interval.

[0078] Set the pairing step interval duration Time difference Divided by interval: ,in, , , K The maximum number of segments, The pairing step interval duration, This is the preset maximum pairing time.

[0079] For the k The pulse pairs within the paired step interval are assigned values, if the time difference of the selected pulse pairs is... Then classify and count it to the first number. Segment step interval duration middle:

[0080] Calculate the first according to the following formula. k Total number of pulse pairing bit values ​​within a pairing step interval:

[0081] Calculate the first according to the following formula. k Pairing step interval duration Total number of error bits:

[0082] in, The time difference between two response events in the paired event set. The numerical value for each pulse pair, This represents the total number of bit values ​​for pulse pairing. For the judgment value, This represents the total number of error bits.

[0083] Step S2076, according to the first k Pairing step interval duration The phase error rate is calculated from the total number of pulse pairings and the total number of erroneous bits within the pulse.

[0084] The phase error rate is calculated using the following formula:

[0085] in, This represents the phase error rate.

[0086] This yields a curve showing the relationship between "pairing step interval duration and phase error rate".

[0087] Step S2077, for the phase bit error rate sequence Perform a Fast Fourier Transform (FFT) to obtain frequency difference information. Generally, the frequency component with the largest amplitude is selected as the estimate.

[0088] According to some embodiments, due to the limited number of sampling points in the original phase error rate data, the spectral curve obtained by Fast Fourier Transform (FFT) has insufficient resolution and poor waveform smoothness, making it difficult to accurately identify frequency difference characteristic peaks. Therefore, this application can perform zero-padding preprocessing on the phase error rate sequence. By padding the end of the original data sequence with zero values, the number of calculation points for spectral analysis is effectively increased. Without increasing the actual amount of sampled data, this significantly improves the spectral resolution and effectively enhances the accuracy and reliability of frequency difference estimation.

[0089] Furthermore, in long-distance (e.g., 250km) quantum key distribution scenarios, the quantum signal strength is significantly reduced due to fiber optic channel attenuation, while background noise interference is greatly enhanced. If the maximum pairing time is set too long, a large amount of invalid noise data will be introduced, leading to a deterioration in the signal-to-noise ratio (SNR) of frequency difference estimation; if it is set too short, the amount of effective statistical data is insufficient to support high-precision frequency difference extraction. To address this, this application introduces an adaptive SNR evaluation mechanism, using the ratio of the frequency difference characteristic peak amplitude to the background noise floor amplitude as the SNR evaluation index. It iterates through the statistical data under different maximum pairing times and calculates the corresponding SNR, selecting the time with the highest SNR as the optimal maximum pairing time. This eliminates low-quality noise data, retains high-purity effective signals, and significantly improves the accuracy of frequency difference estimation and the robustness of the system in long-distance transmission scenarios.

[0090] In step S208, the frequency difference information is used for the pulse pairs of the X basis vector response events to complete frequency difference estimation and phase compensation.

[0091] Step S2081: Calculate the phase compensation amount based on the frequency difference information. .

[0092] in, Let X be the time difference between the X basis vector pulse pairs.

[0093] Step S2082, based on the event time difference of the pulse pairs of the X basis vector response events. and phase compensation amount The phase of the pulse pair of the X basis vector response event is post-processed and corrected to obtain the phase value. This completes frequency difference estimation and phase compensation.

[0094]

[0095] The frequency difference estimation and phase compensation method of this application is used to improve the phase error problem of the AMDI-QKD system.

[0096] After phase compensation is completed, the asynchronous paired measurement device-independent quantum key distribution system continues to perform key screening, error correction and privacy amplification operations in accordance with the AMDI-QKD protocol, and finally forms a secure key.

[0097] Figure 4 This is a comparison diagram of the X-basis phase error rate before and after frequency difference estimation and phase compensation in an embodiment of this application.

[0098] In an asynchronous paired measurement device-independent quantum key distribution system, two compact, narrow-linewidth lasers were used as light sources for experimental testing. The frequency difference between the light sources was 70 MHz, and the signals were transmitted through a 250 km optical fiber and then detected by a single-photon avalanche diode (APD).

[0099] like Figure 4 As shown, each point represents the result of data analysis at a set time interval. The horizontal axis represents the number of data points collected, and the vertical axis represents the X-basis phase error rate. For example, in the 20th set time interval, the X-basis phase error rate was 50% before compensation and 29% after compensation. It is evident that under uncompensated conditions, due to the large frequency difference, the coherence between the two user light sources is severely disrupted, causing the X-basis phase error rate to deteriorate to nearly 50%, rendering the system unable to transmit any effective information.

[0100] After frequency difference compensation, the phase error rate was reduced to about 29%, close to the inherent error rate threshold of 25%.

[0101] The experimental results not only verified the applicability of the compensation scheme of this application to single-photon avalanche diodes (APDs), but also confirmed its feasibility in long-distance optical fiber transmission scenarios, and demonstrated the system's good tolerance to a wider range of light source frequency differences.

[0102] Through the above exemplary embodiments, this application provides a frequency difference estimation and phase compensation method and an asynchronous pairing measurement device-independent quantum key distribution system. It uses the published residual high-intensity signal state quantum information response events for frequency difference analysis. By eliminating the dependence on time-division reference light, it avoids the complexity of adjusting the power ratio of reference light and signal light and reduces the interference of scattering noise. This technical approach maximizes the quantum transmission duty cycle, thereby improving the overall system performance. This application improves the utilization rate of existing quantum resources and expands the dynamic frequency difference tolerance range between laser sources by publishing the pairwise repeated pairing mechanism of the signal state quantum signal response events, while supporting a longer effective transmission distance. This application also reduces the high coherence requirements of the light source and simplifies the system architecture complexity. Furthermore, this application introduces a signal zero-padding preprocessing method to improve spectral resolution. This application is applicable to APDs with low detection efficiency, further improving the performance of practical asynchronous measurement device-independent quantum key distribution systems.

[0103] Figure 5 This diagram illustrates the structure of an electronic device provided in this application.

[0104] See Figure 5 , Figure 5 An electronic device is provided, including a processor and a memory. The memory stores computer instructions, which, when executed by the processor, cause the processor to perform the computer instructions to achieve the following: Figure 2 The method and its detailed scheme are shown.

[0105] It should be understood that the above-described device embodiments are merely illustrative, and the device disclosed in this application can also be implemented in other ways. For example, the division of units / modules in the above embodiments is only a logical functional division, and there may be other division methods in actual implementation. For example, multiple units, modules, or components may be combined, or integrated into another system, or some features may be ignored or not executed.

[0106] Furthermore, unless otherwise specified, the functional units / modules in the various embodiments of this application can be integrated into one unit / module, or each unit / module can exist physically separately, or two or more units / modules can be integrated together. The integrated units / modules described above can be implemented in hardware or as software program modules.

[0107] When an integrated unit / module is implemented in hardware, the hardware can be digital circuits, analog circuits, etc. The physical implementation of the hardware structure includes, but is not limited to, transistors, memristors, etc. Unless otherwise specified, the processor or chip can be any suitable hardware processor, such as a CPU, GPU, FPGA, DSP, and ASIC, etc. Unless otherwise specified, on-chip cache, off-chip memory, and storage can be any suitable magnetic or magneto-optical storage medium, such as resistive random access memory (RRAM), dynamic random access memory (DRAM), static random access memory (SRAM), enhanced dynamic random access memory (EDRAM), high-bandwidth memory (HBM), hybrid memory cube (HMC), etc.

[0108] If the integrated unit / module is implemented as a software program module and sold or used as an independent product, it can be stored in a computer-readable storage device (CMD). Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments disclosed herein. The aforementioned memory includes various media capable of storing program code, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard drive, magnetic disk, or optical disk.

[0109] This application also provides a non-transitory computer storage medium storing a computer program, which, when executed by multiple processors, causes the processors to perform actions such as... Figure 2 The method and its detailed scheme are shown.

[0110] It should be clearly understood that this application describes how specific examples are formed and used, but this application is not limited to any details of these examples. Rather, based on the teachings of the disclosure of this application, these principles can be applied to many other embodiments.

[0111] Furthermore, it should be noted that the above figures are merely illustrative representations of the processes included in the method according to exemplary embodiments of this application, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0112] Exemplary embodiments of this application have been specifically shown and described above. It should be understood that this application is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this application is intended to cover various modifications and equivalent arrangements that fall within the objectives and scope of the appended claims.

Claims

1. A method for frequency difference estimation and phase compensation for asynchronous paired measurement device-independent quantum key distribution, characterized in that, include: Receive quantum signal light pulses sent by both communicating parties, wherein the light intensity of the quantum signal light pulses includes signal state, decoy state and vacuum state; Polarization modulation and single-photon interference are performed on the quantum signal light pulses sent by the two communicating parties to obtain the detection response event; The detection response events are filtered, and response events with light intensity combinations of <signal state|decoy state> and <decoy state|signal state> are discarded; Perform global nearest neighbor pairing on the remaining response events to determine impulse pairs for the X basis response events and the Z basis response events for key generation; Among the remaining response events, identify the set response events that were not used in the Z basis response events and whose light intensity combination is <signal state|signal state>; Within a preset maximum pairing duration, the set response events are randomly paired in pairs to generate a pairing event set of [2 times signal state, 2 times signal state]. The pairing event set is classified and statistically analyzed according to the pairing step interval duration. A correspondence between the pairing step interval duration and the phase bit error rate is established. The correspondence is then subjected to a fast Fourier transform to extract frequency difference information. The frequency difference information is used for the pulse pairs of the X basis vector response events to complete frequency difference estimation and phase compensation.

2. The frequency difference estimation and phase compensation method as described in claim 1, characterized in that, The step of performing global nearest neighbor pairing on the remaining response events to determine impulse pairs for the X basis vector response events and the Z basis vector response events for key generation includes: The remaining response events are paired with the nearest remaining response events; If the time interval between the remaining response event and the nearest remaining response event is within the maximum pairing time interval, a pulse pair is generated; Pulse pairs with light intensity summing to [signal state, signal state] are selected as the pulse pairs of the Z basis vector response events; Pulse pairs with light intensities summing to [2x decoy state, 2x decoy state] are selected as the pulse pairs for the X basis vector response events.

3. The frequency difference estimation and phase compensation method as described in claim 2, characterized in that, The process of classifying and statistically analyzing the paired event set according to the paired step interval duration, establishing a correspondence between the paired step interval duration and the phase bit error rate, and performing a fast Fourier transform on the correspondence to extract frequency difference information includes: The phase difference of the quantum signal light pulses between the two communicating parties in the pairing event set is calculated according to the following formula: 、 The relative phase difference between the two communicating parties is calculated using the following formula: The phase quantity is calculated by taking the modulus of the relative phase difference according to the following formula: Select the phase quantity as 0 or The phase quantity is calculated, the corresponding bit value of the corresponding pulse pair is calculated, and the bit value is compared with the preset reference bit value to determine whether the corresponding pulse pair is correct and obtain the judgment value; Set the pairing step interval duration, and calculate the first step based on the pairing step interval duration and the judgment value. k The total number of pulse pairing bits and the total number of error bits within the pairing step interval; According to the k The phase error rate is calculated by the total number of pulse pairing bits and the total number of error bits within the pairing step interval. in, The phase difference of the quantum signal light pulse of one of the communicating parties. The phase difference of the quantum signal light pulse of the other party in the communication is given by the given statement. One of the communicating parties time, The phase of the quantum signal light pulse at a given moment. The other party in the communication time, The phase of the quantum signal light pulse at a given moment. For [2x signal state, 2x signal state], The relative phase difference between the two communicating parties. The phase quantity, , , K The maximum number of segments, The pairing step interval duration, The preset maximum pairing time, , .

4. The frequency difference estimation and phase compensation method as described in claim 3, characterized in that, The selected phase quantity is 0 or The phase quantity is calculated, the corresponding bit value of the corresponding pulse pair is calculated, and the bit value is compared with the preset reference bit value to determine whether the corresponding pulse pair is correct, and a judgment value is obtained, including: Select phase quantity as 0 or The pulse pairs are considered valid events; Calculate the bit value of the pulse pair corresponding to the valid event; The bit value is compared with a preset reference bit value; If the bit value matches the preset reference bit value, the valid event is determined to be a correct event, and the judgment value of the pulse pair of the valid event is determined. =0; If the bit value is inconsistent with the preset reference bit value, the valid event is determined to be an erroneous event, and the judgment value of the pulse pair of the valid event is determined. =1.

5. The frequency difference estimation and phase compensation method as described in claim 4, characterized in that, The process involves setting the pairing step interval duration and calculating the first step based on the pairing step interval duration and the judgment value. k The total number of pulse pairing bits and the total number of error bits within the pairing step interval include: Set the pairing step interval duration Time difference By interval Division; For the k Each pulse pair within the specified pairing step interval is assigned a value: Calculate the first according to the following formula. k The total number of pulse pairing bit values ​​within the duration of the pairing step interval: Calculate the first according to the following formula. k The total number of error bits within the duration of the pairing step interval: in, The time difference between two response events in the paired event set. The numerical value for each pulse pair, The total number of bit values ​​for the pulse pairing. The judgment value is... The total number of error bits.

6. The frequency difference estimation and phase compensation method as described in claim 5, characterized in that, According to the first k The phase error rate is calculated by considering the total number of pulse pairing bits and the total number of erroneous bits within the pairing step interval, including: The phase error rate is calculated using the following formula: in, The phase error rate is denoted as .

7. The frequency difference estimation and phase compensation method as described in claim 1, characterized in that, The step of using the frequency difference information for the pulse pairs of the X basis vector response events to complete frequency difference estimation and phase compensation includes: Calculate the phase compensation amount based on the frequency difference information; Based on the event time difference of the pulse pairs of the X basis vector response event and the phase compensation amount, the phase of the pulse pairs of the X basis vector response event is post-processed and corrected.

8. An asynchronous paired measurement device-independent quantum key distribution system, characterized in that, include: A first transmitting end and a second transmitting end, each comprising: A laser source, used to output laser light; Intensity and phase encoding components are used to modulate the intensity and encode the phase of the laser to generate quantum signal light pulses with light intensities in signal state, decoy state, and vacuum state; An optical attenuator is used to attenuate the encoded quantum signal light pulse to the level of a single photon before sending it into the transmission channel. A measurement terminal, used to perform the frequency difference estimation and phase compensation method as described in any one of claims 1-7, wherein the measurement terminal comprises: A polarization control component is used to adjust the polarization state of the transmitted quantum signal light pulses so that the quantum signal light pulses output by the first transmitting end and the second transmitting end are transmitted in the same polarization state. A beam splitter, connected to the polarization control component, is used to cause single-photon interference of the quantum signal light pulses output by the first transmitting end and the second transmitting end; The first and second detectors are used to acquire the interference results and output the detection response event. The processor, connected to the first and second detectors, is used to filter the detection response events, discarding response events with light intensity combinations of <signal state|decoy state> and <decoy state|signal state>; perform global nearest neighbor pairing on the remaining response events to determine pulse pairs for X-basis response events and Z-basis response events for key generation; among the remaining response events, determine the set response events that are not used for the Z-basis response events and have light intensity combinations of <signal state|signal state>; within a preset maximum pairing duration, perform arbitrary pairwise repeated pairing on the set response events to generate a pairing event set of [2 times signal state, 2 times signal state]; classify and statistically analyze the pairing event set according to the pairing step interval duration, establish the correspondence between the pairing step interval duration and the phase bit error rate, perform a fast Fourier transform on the correspondence, and extract frequency difference information; use the frequency difference information for the pulse pairs of the X-basis response events to complete frequency difference estimation and phase compensation.

9. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors perform the method as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1-7.

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