Low-frequency synchronization signal synchronization method, device and equipment based on BB84 protocol

Abstract

The invention provides a low-frequency synchronization signal synchronization method, device and equipment based on a BB84 protocol, and relates to the technical field of quantum communication. The method comprises the following steps: generating a high-frequency reference signal and a low-frequency synchronization signal; triggering a first group of random coding bases to perform quantum state coding on the to-be-sent information according to the high-frequency reference signal; transmitting a quantum state code to a receiving end according to the frequency of the high-frequency reference signal; modulating the low-frequency synchronizing signal to a preset optical carrier and transmitting the modulated low-frequency synchronizing signal to a receiving end, extracting the low-frequency synchronizing signal by the receiving end, performing frequency conversion on the low-frequency synchronizing signal according to the frequency of the high-frequency reference signal to generate a target high-frequency signal, and triggering a second group of random coding bases to decode the quantum state code by the target high-frequency signal to obtain decoding information; and negotiating the first group of random coding bases, the second group of random coding bases, the to-be-sent information and the decoding information with a receiving end to generate a quantum key. According to the invention, the bit error rate and the eavesdropping misjudgment risk can be reduced.

Description

Technical Field

[0001] This application relates to the field of quantum communication technology, and more specifically, to a method, apparatus, and device for synchronizing low-frequency synchronization signals based on the BB84 protocol. Background Technology

[0002] Quantum key distribution (QKD), as one of the core technologies of quantum communication, relies on the combination of quantum physical properties and protocol design for its security. QKD systems based on the decoy state BB84 protocol have become the mainstream solution in the industry due to their outstanding anti-eavesdropping capabilities.

[0003] Traditional QKD devices rely on high-frequency synchronization signals (such as 100kHz synchronization signals for GHz-level devices) to ensure time synchronization accuracy, thereby ensuring the accuracy and security of key distribution.

[0004] However, in emerging application scenarios such as integrated sensing, QKD devices need to work in conjunction with sensors driven by low-frequency synchronization signals. Therefore, the frequency of the synchronization signal needs to be reduced to the 1kHz level to meet the cross-system timing compatibility requirements. However, directly using low-frequency synchronization signals will cause frame misalignment and increase the bit error rate. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of the prior art by providing a low-frequency synchronization signal synchronization method, apparatus, and device based on the BB84 protocol, so as to reduce the bit error rate and the risk of misjudgment of eavesdropping.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows: In a first aspect, embodiments of this application provide a low-frequency synchronization signal synchronization method based on the BB84 protocol, applied to the transmitter of a quantum communication system, the method comprising: Generate a high-frequency reference signal and a low-frequency synchronization signal; The first set of random coding bases is triggered according to the high-frequency reference signal to perform quantum state coding on the information to be transmitted, and the quantum state coding is sent to the receiving end of the quantum communication system. The low-frequency synchronization signal is modulated onto a preset optical carrier, and a target optical carrier carrying the low-frequency synchronization signal is transmitted to the receiving end, so that the receiving end can extract the low-frequency synchronization signal from the target optical carrier. The high-frequency reference signal frequency is sent to the receiving end so that the receiving end performs frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a target high-frequency signal, and triggers a second set of random coding bases to decode the quantum state code according to the target high-frequency signal to obtain decoded information; The receiving end negotiates the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitting end and the receiving end, respectively.

[0007] Optionally, generating the high-frequency reference signal and the low-frequency synchronization signal includes: Generate the first high-frequency signal; The first high-frequency signal is down-frequencyd to generate the low-frequency synchronization signal; Based on the delay between the first high-frequency signal and the low-frequency synchronization signal, delay compensation is performed on the first high-frequency signal to generate the high-frequency reference signal.

[0008] Optionally, the method further includes: Obtain the channel state parameters of the quantum channel between the transmitter and the receiver; the quantum channel is used to transmit the quantum state encoding; The parameters of the high-frequency reference signal and the low-frequency synchronization signal are adjusted according to the signal state parameters.

[0009] Secondly, embodiments of this application also provide a low-frequency synchronization signal synchronization method based on the BB84 protocol, applied to the receiver of a quantum communication system, the method comprising: The frequency and quantum state encoding of the target optical carrier and high-frequency reference signal transmitted by the transmitter of the quantum communication system are obtained. A low-frequency synchronization signal is extracted from the target optical carrier, and the low-frequency synchronization signal is frequency-converted according to the frequency of the high-frequency reference signal to generate a target high-frequency signal; Based on the target high-frequency signal, the second set of random coding bases is triggered to decode the quantum state encoding to obtain the decoded information; The transmitter negotiates with the receiver on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitter and the receiver, respectively. The target optical carrier, the high-frequency reference signal, the quantum state encoding, the first set of random encoding bases, and the information to be transmitted are generated using the method described in any one of the first aspects.

[0010] Optionally, the step of frequency conversion of the low-frequency synchronization signal based on the frequency of the high-frequency reference signal to generate the target high-frequency signal includes: Based on the frequency of the high-frequency reference signal, the low-frequency synchronization signal is subjected to phase-locked loop frequency multiplication to generate a second high-frequency signal; Based on the delay between the second high-frequency signal and the low-frequency synchronization signal, delay compensation is performed on the second high-frequency signal to generate the target high-frequency signal.

[0011] Optionally, the step of performing delay compensation on the second high-frequency signal based on the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal includes: The electrical delay line is controlled based on the delay of the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

[0012] Optionally, the step of performing delay compensation on the second high-frequency signal based on the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal includes: The phase-locked loop is controlled based on the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

[0013] Thirdly, embodiments of this application also provide a low-frequency synchronization signal synchronization device based on the BB84 protocol, applied to the transmitter of a quantum communication system, the device comprising: The signal generation module is used to generate high-frequency reference signals and low-frequency synchronization signals; The encoding processing module is used to trigger the first set of random encoding bases to perform quantum state encoding on the information to be transmitted based on the high-frequency reference signal, and to send the quantum state encoding to the receiving end of the quantum communication system; A signal synchronization module is used to modulate the low-frequency synchronization signal onto a preset optical carrier and transmit the target optical carrier carrying the low-frequency synchronization signal to the receiving end, so that the receiving end can extract the low-frequency synchronization signal from the target optical carrier. The frequency transmission module is used to transmit the frequency of the high-frequency reference signal to the receiving end, so that the receiving end can perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a target high-frequency signal, and trigger a second set of random coding bases to decode the quantum state code according to the target high-frequency signal to obtain decoded information. The first negotiation module is used to negotiate with the receiving end on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information, and to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitting end and the receiving end, respectively.

[0014] Optionally, the signal generation module is specifically used to generate a first high-frequency signal; down-convert the first high-frequency signal to generate the low-frequency synchronization signal; and perform delay compensation on the first high-frequency signal based on the delay between the first high-frequency signal and the low-frequency synchronization signal to generate the high-frequency reference signal.

[0015] Optionally, the device further includes: The parameter adjustment module is used to acquire the channel state parameters of the quantum channel between the transmitter and the receiver; the quantum channel is used to transmit the quantum state encoding; and to adjust the parameters of the high-frequency reference signal and the low-frequency synchronization signal according to the signal state parameters.

[0016] Fourthly, embodiments of this application also provide a low-frequency synchronization signal synchronization device based on the BB84 protocol, applied at the receiving end of a quantum communication system, the device comprising: The information receiving module is used to acquire the frequency and quantum state encoding of the target optical carrier and high-frequency reference signal transmitted by the transmitter of the quantum communication system. The frequency conversion module is used to extract a low-frequency synchronization signal from the target optical carrier, and perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a target high-frequency signal. The decoding module is used to decode the quantum state encoding based on the target high-frequency signal triggering the second set of random coding bases to obtain decoded information; The second negotiation module is used to negotiate with the transmitter on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information, and to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitter and the receiver respectively. The target optical carrier, the high-frequency reference signal, the quantum state encoding, the first set of random encoding bases, and the information to be transmitted are generated using the apparatus described in the third aspect.

[0017] Optionally, the frequency conversion module is specifically used to perform phase-locked loop frequency multiplication on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a second high-frequency signal; and to perform delay compensation on the second high-frequency signal according to the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

[0018] Optionally, the frequency conversion module is further configured to control the electrical delay line based on the delay of the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

[0019] Optionally, the frequency conversion module is further configured to control the phase-locked loop based on the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

[0020] Fifthly, embodiments of this application also provide a terminal device, including: a processor, a storage medium, and a bus. The storage medium stores program instructions executable by the processor. When the terminal device is running, the processor communicates with the storage medium via the bus. The processor executes the program instructions to perform the steps of the low-frequency synchronization signal synchronization method as described in any of the first aspects, or the steps of the low-frequency synchronization signal synchronization method as described in any of the second aspects.

[0021] Sixthly, embodiments of this application also provide a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the low-frequency synchronization signal synchronization method as described in any of the first aspects, or the steps of the low-frequency synchronization signal synchronization method as described in any of the second aspects.

[0022] The beneficial effects of this application are: The low-frequency synchronization signal synchronization method, apparatus, and equipment based on the BB84 protocol provided in this application transmit the low-frequency synchronization signal to the receiving end through an optical channel. The low-frequency synchronization signal is frequency-converted based on the frequency of a high-frequency reference signal to generate a target high-frequency signal. The target high-frequency signal and the low-frequency synchronization signal are periodically phase-aligned to ensure that the phases of the high-frequency reference signal and the target high-frequency signal remain consistent. The received photon pulses are aligned with the trigger edges of the target high-frequency signal to ensure that the receiving end allocates the received photon pulses to the correct time slots, avoiding frame misalignment. The modulator is controlled to switch the coding basis vector based on the target high-frequency signal, ensuring that the coding basis vector selection at the receiving end is strictly aligned with the time slot of the photon pulse, reducing the bit error rate and the risk of misjudgment due to timing deviations. The target high-frequency signal recovered from the low-frequency synchronization signal can still quickly capture channel disturbances, ensuring the real-time monitoring capability of the QKD system. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 Architecture of the quantum communication system provided in the embodiments of this application Figure 1 ; Figure 2Architecture of the quantum communication system provided in the embodiments of this application Figure 2 ; Figure 3 A flowchart illustrating the low-frequency synchronization signal synchronization method provided in this application embodiment. Figure 1 ; Figure 4 A flowchart illustrating the low-frequency synchronization signal synchronization method provided in this application embodiment. Figure 2 ; Figure 5 A schematic diagram of the structure of a low-frequency synchronization signal synchronization device based on the BB84 protocol provided in this application embodiment. Figure 1 ; Figure 6 A schematic diagram of the structure of a low-frequency synchronization signal synchronization device based on the BB84 protocol provided in this application embodiment. Figure 2 ; Figure 7 A schematic diagram of a terminal device provided in an embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0026] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0027] Furthermore, the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Additionally, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0029] To better understand this scheme, the architecture of the quantum communication system used in this application will be introduced below.

[0030] In one possible implementation, Figure 1 Architecture of the quantum communication system provided in the embodiments of this application Figure 1 ,like Figure 1 As shown, the quantum communication system includes a transmitter (Alice) and a receiver (Bob).

[0031] The transmitting end may include: a synchronization signal generation module, a quantum state encoding module, and a quantum key generation module; the receiving end may include: a synchronization signal receiving module, a quantum state decoding module, and a quantum key generation module.

[0032] The quantum state encoding module and the quantum state decoding module communicate using a quantum channel, while the synchronization signal generation module and the synchronization signal receiving module communicate using an optical channel. In addition, the transmitter and receiver also negotiate information directly through a classical channel.

[0033] Specifically, the synchronization signal generation module generates a high-frequency reference signal and a low-frequency synchronization signal. The high-frequency reference signal and the low-frequency synchronization signal are periodically phase-aligned. The transmitter emits photon pulses under the control of the high-frequency reference signal. The photon pulses are the physical carriers of quantum state encoding. The modulator switches the encoding basis vector based on the high-frequency reference signal and encodes the information to be transmitted according to the encoding basis vector. It determines the polarization encoding or phase encoding of the information to be transmitted and modulates the polarization state or phase state of the photon pulse according to the polarization encoding or phase encoding to send photons carrying quantum state encoding to the quantum state decoding module. The time interval between the laser generating photon pulses is consistent with the time interval between the modulator switching the encoding basis vector, that is, the photon pulses and the selection of the encoding basis vector are precisely aligned, and the quantum state encoding is either polarization encoding or phase encoding.

[0034] In existing technologies, the low-frequency synchronization signal transmitted from the transmitter to the receiver faces the following problems: 1. Accumulation of time synchronization error: The long time interval of low frequency synchronization signal is susceptible to transmission delay and moderate drift, which causes the receiver to allocate the received quantum state code to the wrong time slot, resulting in frame misalignment; 2. Basis selection misalignment: The BB84 protocol relies on precise basis selection timing. Insufficient synchronization accuracy between the high-frequency reference signal and the low-frequency synchronization signal will disrupt the basis selection timing, leading to basis selection misalignment, increasing the bit error rate and the risk of false alarms. 3. Lag in eavesdropping detection: High-frequency reference signals can quickly capture channel disturbances, while low-frequency synchronization signals, due to their reduced frequency, prevent the system from capturing disturbances in real time. Eavesdropping behavior is only detected after multiple synchronization cycles, giving attackers enough time to eavesdrop undetected, thus extending the attack window and weakening the real-time monitoring capabilities of the QKD system.

[0035] In this scheme, the synchronization signal generation module sends the low-frequency synchronization signal to the synchronization signal receiving module through the optical channel. The transmitting end also sends the frequency of the high-frequency reference signal to the receiving end through the classical signal, so that the synchronization signal generation module performs frequency conversion on the low-frequency synchronization signal based on the frequency of the high-frequency reference signal to generate the target high-frequency signal. The target high-frequency signal and the low-frequency synchronization signal are periodically phase aligned, thereby ensuring that the phase of the high-frequency reference signal and the target high-frequency signal remains consistent.

[0036] The quantum state decoding module aligns the received photon pulses with the trigger edges of the target high-frequency signal, ensuring that the receiver assigns the received quantum state encoding to the correct time slot and avoids frame misalignment. Based on the target high-frequency signal, the modulator controls the switching of the encoding basis vector, ensuring that the encoding basis vector selection at the receiver is strictly aligned with the time slot of the photon pulse, reducing the bit error rate and risk of misjudgment due to timing deviations. The target high-frequency signal recovered based on the low-frequency synchronization signal can still quickly capture channel disturbances, ensuring the real-time monitoring capability of the QKD system.

[0037] In some embodiments, such as Figure 1 As shown, the synchronization signal generation module may include: a high-precision clock, a synchronization pulse generation unit, and an electro-optic modulation unit.

[0038] The high-precision clock uses a moderately stable atomic clock-level reference, providing a long-term stable frequency reference and laying the foundation for time base synchronization of the entire system.

[0039] The synchronization pulse generation unit generates a high-frequency reference signal and a low-frequency synchronization signal based on direct digital frequency synthesis technology. The electro-optic modulation unit uses a high-speed electro-optic modulator to modulate the low-frequency synchronization signal onto an optical carrier and transmits it to the receiver via optical fiber. Furthermore, the quantum channel and the optical channel are transmitted together via wavelength division multiplexing (WDM) technology to ensure the physical compatibility of the transmission link.

[0040] Furthermore, the synchronization signal generation module may also include an adaptive control module, which runs a dynamic adaptive algorithm through an embedded processor, collects the state parameters of the quantum channel in real time, and dynamically adjusts the signal parameters of the high-frequency reference signal and the low-frequency synchronization signal based on a preset optimization model to achieve intelligent matching of the time-varying characteristics of the channel.

[0041] For example, the state parameters of a quantum channel may include one or more of the following: bit error rate, photon arrival time jitter, and signal loss fluctuation. These state parameters can be determined through negotiation using a classical channel. Signal parameters may include at least frequency, and may also include parameters such as intensity and phase.

[0042] In some embodiments, such as Figure 1 As shown, the synchronization signal receiving module may include: a photoelectric detection unit, a phase-locked loop frequency multiplier unit, and a delay calculation and delay compensation unit.

[0043] The photoelectric detection unit extracts the low-frequency synchronization signal from the optical carrier through a high-sensitivity photoelectric detector, thus completing the photoelectric-to-electric conversion.

[0044] The phase-locked loop (PLL) frequency multiplier unit uses PLL technology to construct a frequency multiplier circuit, which converts the low-frequency synchronization signal into a clock signal that is synchronized with the high-frequency reference signal at the transmitting end. The phase-locking mechanism eliminates the phase error in the frequency conversion process, providing a precise time base for quantum state decoding at the receiving end.

[0045] The delay calculation and delay compensation unit calculates the delay of the low-frequency synchronization signal during signal transmission and phase-locked frequency multiplication, and performs delay compensation on the clock signal based on the delay to generate the target high-frequency signal.

[0046] In another possible implementation, Figure 2 Architecture of the quantum communication system provided in the embodiments of this application Figure 2 ,like Figure 2 As shown, the synchronization signal generation module may include: a high-precision clock, a synchronization pulse generation unit, an electro-optic modulation unit, and a frequency reduction unit.

[0047] The synchronization pulse generation unit is used to generate a first high-frequency signal. The frequency reduction unit includes a delay calculation and delay compensation unit and a frequency reduction subunit. The frequency reduction subunit reduces the frequency of the first high-frequency signal to generate a low-frequency synchronization signal. The delay calculation and delay compensation unit calculates the delay between the low-frequency synchronization signal and the first high-frequency signal, and performs delay compensation on the first high-frequency signal according to the delay to generate a high-frequency reference signal.

[0048] This approach is compatible with the high-frequency reference signal design standards of existing QKD devices, eliminating the need to modify the core timing module. The low-frequency synchronization signal generation function can be achieved simply by upgrading the peripheral circuitry.

[0049] Based on the above introduction to quantum communication systems, the following describes the specific implementation of a low-frequency synchronization signal synchronization method based on the BB84 protocol applied to the transmitter of a quantum communication system, in conjunction with specific embodiments.

[0050] In one possible implementation, Figure 3A flowchart illustrating the low-frequency synchronization signal synchronization method provided in this application embodiment. Figure 1 ,like Figure 3 As shown, the method may include: S110 generates a high-frequency reference signal and a low-frequency synchronization signal.

[0051] In this embodiment, as Figure 1 As shown, the synchronization signal generation module at the transmitting end generates a high-frequency reference signal based on a high-precision clock source, and performs frequency division processing on the high-frequency reference signal to generate a low-frequency synchronization signal.

[0052] S120. Trigger the first set of random coding bases to encode the information to be transmitted into quantum states based on the high-frequency reference signal, and send the quantum state codes to the receiving end of the quantum communication system.

[0053] In this embodiment, the rising edge of the high-frequency reference signal serves as the benchmark for quantum state encoding. The laser at the transmitting end generates photon pulses based on the rising edge of the high-frequency reference signal, and the modulator at the transmitting end generates a first set of random encoding bases based on the rising edge of the high-frequency reference signal.

[0054] The laser at the transmitting end determines the number of photon pulses in each group based on the frequency of the high-frequency reference signal. The modulator at the transmitting end determines the number of coding bases in the first group of random coding bases in each group based on the frequency of the high-frequency reference signal. The number of photon pulses in each group is equal to the number of coding bases in each group, and each photon pulse corresponds to one coding base. The photon pulses and coding bases correspond one-to-one in sequence. The higher the frequency of the high-frequency reference signal, the fewer the number of photon pulses and coding bases in each group. For example, when the frequency of the high-frequency reference signal is the first frequency, the number of photon pulses and coding bases between every two rising edges (every two benchmarks) is 100. When the frequency of the high-frequency reference signal rises to the second frequency, the number of photon pulses and coding bases between every two rising edges (every two benchmarks) decreases to 50.

[0055] The laser at the transmitting end triggers the transmission of a group of photon pulses based on each rising edge of a high-frequency reference signal. Based on the first random coding basis of each group generated by the modulator, each group of photon pulses is quantum-state encoded to generate photon pulses carrying quantum-state encoded information. The photon pulses carrying quantum-state encoded information are then sent to the quantum-state decoding module at the receiving end through a quantum channel.

[0056] The coding basis is divided into rectangular basis and diagonal basis. For example, the rectangular basis controls the photon pulse to be horizontally polarized for data 0 and vertically polarized for data 1. The diagonal basis controls the photon pulse to be polarized at 45° for data 0 and at 135° for data 1.

[0057] S130. Modulate the low-frequency synchronization signal onto a preset optical carrier and transmit the target optical carrier carrying the low-frequency synchronization signal to the receiving end so that the receiving end can extract the low-frequency synchronization signal from the target optical carrier.

[0058] In this embodiment, the photoelectric modulation unit at the transmitting end modulates the low-frequency synchronization signal onto a preset optical carrier to obtain a target optical carrier. The target optical carrier is then transmitted to the photoelectric detection unit at the receiving end through an optical channel, so that the photoelectric detection unit can extract the low-frequency synchronization signal from the target optical carrier.

[0059] S140. Send the frequency of the high-frequency reference signal to the receiving end so that the receiving end can perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate the target high-frequency signal, and trigger the second set of random coding basis to decode the quantum state code according to the target high-frequency signal to obtain the decoded information.

[0060] In this embodiment, the transmitting end transmits the frequency of the high-frequency reference signal to the receiving end through a classical channel. The phase-locked loop (PLL) frequency multiplier unit of the receiving end uses PLL technology to construct a frequency multiplier circuit to convert the low-frequency synchronization signal into a clock signal synchronized with the high-frequency reference signal of the transmitting end. The delay calculation and delay compensation unit of the receiving end calculates the delay of the low-frequency synchronization signal during signal transmission and PLL frequency multiplication, and performs delay compensation on the clock signal based on the delay to generate the target high-frequency signal.

[0061] After receiving the photon pulse and generating the target high-frequency signal, the quantum state decoding module at the receiving end groups the photon pulses according to their frequency. The rising edge of the target high-frequency signal is used as a benchmark to align each group of photon pulses with the rising edge of the target high-frequency signal. The modulator at the receiving end generates a second set of random coding bases based on the target high-frequency signal and decodes the photon pulses based on the second set of random coding bases to obtain the decoded information.

[0062] If the second set of random coding bases is the same as the coding base of the first set of random coding bases at the same position, then the data decoded at that position is consistent with the data in the information to be sent. If the second set of random coding bases is different from the coding base of the first set of random coding bases at the same position, then the data decoded at that position may be the same as or different from the data in the information to be sent.

[0063] For example, if the fifth bit of the information to be transmitted is 0, and it is encoded as horizontally polarized using a rectangular basis, and the receiving end receives a horizontally polarized photon pulse, if the fifth bit of the second set of random coding basis is a rectangular basis, then the data 0 is obtained by decoding based on the horizontally polarized photon pulse; if the fifth bit of the second set of random coding basis is a diagonal basis, then the data 0 or 1 is obtained by decoding based on the horizontally polarized photon pulse.

[0064] S150. Negotiate with the receiver on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information. Determine the target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitter and receiver respectively.

[0065] In this embodiment, based on the BB84 protocol, the receiver and transmitter negotiate the first and second sets of random coding bases to determine the positions using the same coding base. Then, based on the positions of the same coding base, the receiver determines the decoding information at the corresponding positions and selects a portion of the decoding information from the corresponding positions to send to the transmitter. The transmitter determines whether the portion of the decoding information at the corresponding positions is consistent with the information at the corresponding positions in the information to be sent. If they are consistent, it is determined that the transmitted quantum state encoding has not been eavesdropped. Then, the transmitter generates a quantum key based on the remaining information in the information to be sent at the corresponding positions, and the receiver generates a quantum key based on the remaining information in the decoding information at the corresponding positions. This realizes quantum key distribution based on the BB84 protocol.

[0066] The low-frequency synchronization signal synchronization method based on the BB84 protocol provided in the above embodiments transmits the low-frequency synchronization signal to the receiving end through an optical channel. The low-frequency synchronization signal is frequency-converted based on the frequency of the high-frequency reference signal to generate a target high-frequency signal. The target high-frequency signal and the low-frequency synchronization signal are periodically phase-aligned to ensure that the phases of the high-frequency reference signal and the target high-frequency signal remain consistent. The received photon pulses are aligned with the trigger edges of the target high-frequency signal to ensure that the receiving end allocates the received photon pulses to the correct time slots, avoiding frame misalignment. The modulator is controlled to switch the coding basis vector based on the target high-frequency signal, ensuring that the coding basis vector selection at the receiving end is strictly aligned with the time slot of the photon pulse, reducing the bit error rate and the risk of misjudgment due to timing deviations. The target high-frequency signal recovered from the low-frequency synchronization signal can still quickly capture channel disturbances, ensuring the real-time monitoring capability of the QKD system.

[0067] In one possible implementation, the process of generating the high-frequency reference signal and the low-frequency synchronization signal in S110 above may include: A first high-frequency signal is generated; the first high-frequency signal is down-converted to generate a low-frequency synchronization signal; based on the delay between the first high-frequency signal and the low-frequency synchronization signal, the delay of the first high-frequency signal is compensated to generate a high-frequency reference signal.

[0068] In this embodiment, as Figure 2 As shown, a first high-frequency signal is generated by a synchronization pulse generation unit, and a low-frequency synchronization signal is generated by a frequency reduction subunit. The delay between the low-frequency synchronization signal and the first high-frequency signal is calculated by a delay calculation and delay compensation unit, and the delay of the first high-frequency signal is compensated according to the delay to generate a high-frequency reference signal.

[0069] In this way, without modifying the original synchronization pulse generation device, the existing high-frequency signal can be divided by a cascaded frequency downsampling module to generate a lower-frequency synchronization signal. This achieves low-frequency synchronization without changing the core timing logic of the existing equipment, reducing engineering modification difficulty and adapting to the existing equipment architecture. This solution is particularly suitable for terminal collaboration scenarios with different frequency requirements in multi-device quantum networks. Through the flexible cascading of the transmitter's frequency downsampling module and the receiver's frequency multiplication module, cross-frequency synchronization adaptation between high-frequency and low-frequency devices can be achieved, significantly improving the system's compatibility with heterogeneous network environments.

[0070] In one possible implementation, the method may further include: Obtain the channel state parameters of the quantum channel between the transmitter and receiver; the quantum channel is used to transmit quantum state encoding; adjust the parameters of the high-frequency reference signal and the low-frequency synchronization signal according to the signal state parameters.

[0071] In this embodiment, by acquiring the transmission state data of the quantum state encoding transmitted by the transmitter and the reception state data of the quantum state encoding received by the receiver, the channel state parameters of the quantum channel are determined. The channel state parameters are used to indicate the effect of the quantum channel in transmitting quantum state encoding.

[0072] If the channel state parameters indicate that the quantum channel is poorly transmitting quantum state encoding, the signal state parameters of the high-frequency reference signal can be increased and / or the signal state parameters of the low-frequency synchronization signal can be decreased; if the channel state parameters indicate that the quantum channel is well transmitting quantum state encoding, the signal state parameters of the high-frequency reference signal can be decreased and / or the signal state parameters of the low-frequency synchronization signal can be increased.

[0073] In some embodiments, such as Figure 1 As shown, if the synchronization pulse generation unit is adjustable, the signal state parameters of the high-frequency reference signal and / or the low-frequency synchronization signal can be adjusted according to the signal state parameters, such as... Figure 2 As shown, if the synchronization pulse generation unit is not adjustable, the signal status parameters of the low-frequency synchronization signal can be adjusted according to the signal status parameters.

[0074] In some embodiments, a state parameter threshold range can be set. If the channel state parameter is less than the minimum value of the state parameter threshold range, it is determined that the quantum channel transmits quantum state coding with poor performance. If the channel state parameter is greater than the maximum value of the state parameter threshold range, it is determined that the quantum channel transmits quantum state coding with good performance.

[0075] In other embodiments, changes in channel state parameters can be continuously monitored to determine the effectiveness of quantum state encoding transmitted by the quantum channel.

[0076] Furthermore, by running a dynamic adaptive algorithm through an embedded processor, the state parameters of the quantum channel are collected in real time, and the signal parameters of the high-frequency reference signal and the low-frequency synchronization signal are dynamically adjusted based on a preset optimization model to achieve intelligent matching of the time-varying characteristics of the channel.

[0077] For example, the state parameters of a quantum channel may include one or more of the following: bit error rate, photon arrival time jitter, and signal loss fluctuation. These state parameters can be determined through negotiation using a classical channel. Signal parameters may include at least frequency, and may also include parameters such as intensity and phase.

[0078] The preset optimization model can be a PID control module or a machine learning model.

[0079] For example, the frequency of the high-frequency reference signal can be adjusted based on the channel state of the quantum channel. If the channel state of the quantum channel is poor, such as a high bit error rate or strong photon arrival time jitter, the frequency of the high-frequency reference signal can be increased, thereby increasing the frequency of the rising edge of the trigger photon pulse, reducing the number of photon pulses per group, and increasing the frequency of the target high-frequency signal recovered by the receiver. This shortens the correction interval of the photon pulse at the receiver, suppresses the accumulation of errors caused by transmission delay and clock drift, and improves the time synchronization accuracy.

[0080] For example, the frequency of the low-frequency synchronization signal can be adjusted based on the channel state of the quantum channel. If the channel state of the quantum channel is poor, the frequency of the low-frequency synchronization signal can be reduced, thereby reducing the optical energy of the target optical carrier transmitted through the optical channel and thus reducing interference to the optical signal.

[0081] The low-frequency synchronization signal synchronization method based on the BB84 protocol provided in the above embodiments adjusts signal parameters through a dynamic adaptive algorithm, establishes a dynamic mapping relationship between signal parameters and channel state, realizes closed-loop adjustment of signal parameters, adapts to channel state fluctuations in real time, significantly improves the system's adaptability to the time-varying characteristics of optical fiber channels, reduces the bit error rate caused by channel interference, enhances the anti-interference capability of this scheme in complex transmission environments, and improves the reliability and security of quantum key distribution.

[0082] The following describes the specific implementation of a low-frequency synchronization signal synchronization method based on the BB84 protocol applied to the receiver of a quantum communication system, with reference to specific embodiments.

[0083] In one possible implementation, Figure 4 A flowchart illustrating the low-frequency synchronization signal synchronization method provided in this application embodiment. Figure 2 ,like Figure 4 As shown, the method may include: S210. Obtain the frequency and quantum state encoding of the target optical carrier and high-frequency reference signal transmitted by the transmitter of the quantum communication system.

[0084] In this embodiment, the quantum state code sent by the receiving and transmitting end through the quantum channel, the target optical carrier sent through the optical signal, and the frequency of the high-frequency reference signal sent through the classical signal are specifically referred to in S110~S150 above, and will not be repeated here.

[0085] S220. Extract the low-frequency synchronization signal from the target optical carrier, and perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate the target high-frequency signal.

[0086] In this embodiment, the photoelectric detection unit of the receiving end extracts the low-frequency synchronization signal from the target optical carrier, and the phase-locked loop frequency multiplier unit of the receiving end uses phase-locked loop technology to construct a frequency multiplier circuit to convert the low-frequency synchronization signal into a clock signal synchronized with the high-frequency reference signal of the transmitting end. The delay calculation and delay compensation unit of the receiving end calculates the delay of the low-frequency synchronization signal in the signal transmission and phase-locked loop frequency multiplication process, and performs delay compensation on the clock signal according to the delay to generate the target high-frequency signal.

[0087] S230. Decode the quantum state encoding and benchmark of the second set of random coding basis pairs based on the target high-frequency signal to obtain the decoded information.

[0088] In this embodiment, after the quantum state decoding module of the receiving end receives the photon pulse and generates the target high-frequency signal, it groups the photon pulses according to frequency. The rising edge of the target high-frequency signal is used as a benchmark to align each group of photon pulses with the rising edge of the target high-frequency signal. The modulator of the receiving end generates a second set of random coding bases based on the target high-frequency signal and decodes the photon pulses based on the second set of random coding bases to obtain the decoded information.

[0089] If the second set of random coding bases is the same as the coding base of the first set of random coding bases at the same position, then the data decoded at that position is consistent with the data in the information to be sent. If the second set of random coding bases is different from the coding base of the first set of random coding bases at the same position, then the data decoded at that position may be the same as or different from the data in the information to be sent.

[0090] For example, if the fifth bit of the information to be transmitted is 0, and it is encoded as horizontally polarized using a rectangular basis, and the receiving end receives a horizontally polarized photon pulse, if the fifth bit of the second set of random coding basis is a rectangular basis, then the data 0 is obtained by decoding based on the horizontally polarized photon pulse; if the fifth bit of the second set of random coding basis is a diagonal basis, then the data 0 or 1 is obtained by decoding based on the horizontally polarized photon pulse.

[0091] S240. Negotiate with the transmitter on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information. Determine the target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitter and receiver respectively.

[0092] In this embodiment, based on the BB84 protocol, the receiver and transmitter negotiate the first and second sets of random coding bases to determine the positions using the same coding base. Then, based on the positions of the same coding base, the receiver determines the decoding information at the corresponding positions and selects a portion of the decoding information from the corresponding positions to send to the transmitter. The transmitter determines whether the portion of the decoding information at the corresponding positions is consistent with the information at the corresponding positions in the information to be sent. If they are consistent, it is determined that the transmitted quantum state encoding has not been eavesdropped. Then, the transmitter generates a quantum key based on the remaining information in the information to be sent at the corresponding positions, and the receiver generates a quantum key based on the remaining information in the decoding information at the corresponding positions. This realizes quantum key distribution based on the BB84 protocol.

[0093] The low-frequency synchronization signal synchronization method based on the BB84 protocol provided in the above embodiments transmits the low-frequency synchronization signal to the receiving end through an optical channel. The low-frequency synchronization signal is frequency-converted based on the frequency of the high-frequency reference signal to generate a target high-frequency signal. The target high-frequency signal and the low-frequency synchronization signal are periodically phase-aligned to ensure that the phases of the high-frequency reference signal and the target high-frequency signal remain consistent. The received photon pulses are aligned with the trigger edges of the target high-frequency signal to ensure that the receiving end allocates the received photon pulses to the correct time slots, avoiding frame misalignment. The modulator is controlled to switch the coding basis vector based on the target high-frequency signal, ensuring that the coding basis vector selection at the receiving end is strictly aligned with the time slot of the photon pulse, reducing the bit error rate and the risk of misjudgment due to timing deviations. The target high-frequency signal recovered from the low-frequency synchronization signal can still quickly capture channel disturbances, ensuring the real-time monitoring capability of the QKD system.

[0094] In one possible implementation, the process of S220 converting the low-frequency synchronization signal to a target high-frequency signal based on the frequency of the high-frequency reference signal can include: Based on the frequency of the high-frequency reference signal, the low-frequency synchronization signal is subjected to phase-locked loop frequency multiplication to generate a second high-frequency signal; based on the delay between the second high-frequency signal and the low-frequency synchronization signal, the second high-frequency signal is subjected to delay compensation to generate the target high-frequency signal.

[0095] In this embodiment, the phase-locked loop (PLL) frequency multiplier unit uses PLL technology to construct a frequency multiplier circuit, converting the low-frequency synchronization signal into a second high-frequency signal that is synchronized with the high-frequency reference signal of the transmitter. The phase-locking mechanism eliminates the phase error in the frequency conversion process, providing a precise time base for quantum state decoding at the receiver.

[0096] Since the high-frequency reference signal and the low-frequency synchronization signal are periodic in-phase signals, in order to avoid the delay in the second high-frequency signal generated based on the frequency multiplication of the low-frequency synchronization signal, it is necessary to perform delay compensation on the recovered second high-frequency signal. The delay calculation and delay compensation unit calculates the delay of the low-frequency synchronization signal in the signal transmission and phase-locked frequency multiplication process, and performs delay compensation on the second high-frequency signal based on the delay to generate the target high-frequency signal.

[0097] The low-frequency synchronization signal synchronization method based on the BB84 protocol provided in the above embodiments transmits the phase information of the low-frequency synchronization signal to the high-frequency signal without distortion through a phase-locking mechanism, thereby achieving phase consistency between the low-frequency input signal and the high-frequency output signal. This enhances time synchronization accuracy, provides a precise time base for quantum state decoding, ensures accurate allocation of quantum state encoding within the time slot, avoids frame misalignment problems caused by timing deviations, shortens the detectable time window for potential attacks, and reduces the synchronization correction interval.

[0098] In one possible implementation, the process of delay compensation of the second high-frequency signal based on the delays of the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal may include: Based on the delay of the second high-frequency signal and the low-frequency synchronization signal, the electrical delay line is controlled to generate the target high-frequency signal.

[0099] In this embodiment, an electrical delay line is used to form a delay compensation module. The phase difference between the second high-frequency signal and the low-frequency synchronization signal is calculated. A control signal is generated based on the phase difference. The electrical delay line is controlled by the control signal to perform delay compensation on the second high-frequency signal and generate the target high-frequency signal.

[0100] In another possible implementation, the process of delay compensation of the second high-frequency signal based on the delay of the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal may include: Based on the delay of the second high-frequency signal and the low-frequency synchronization signal, the phase-locked loop is controlled to generate the target high-frequency signal.

[0101] In this embodiment, a phase-locked loop (PLL) is used to construct a delay compensation module. The phase difference between the second high-frequency signal and the low-frequency synchronization signal is calculated, and a control signal is generated based on the phase difference. The PLL is controlled by the control signal to perform delay compensation on the second high-frequency signal and generate the target high-frequency signal.

[0102] Furthermore, an electrical delay line and a phase-locked loop can be used together to form a delay compensation module, which calculates the phase difference between the second high-frequency signal and the low-frequency synchronization signal, generates a control signal based on the phase difference, controls the electrical delay line through the control signal to coarsely adjust the phase delay of the second high-frequency signal, and then controls the phase-locked loop to finely adjust the phase delay of the second high-frequency signal to generate the target high-frequency signal.

[0103] Among them, the electrical delay line can achieve millisecond-level delay compensation, while the phase-locked loop can achieve sub-nanosecond-level delay compensation.

[0104] The low-frequency synchronization signal synchronization method based on the BB84 protocol provided in the above embodiments compensates for the delay of the first high-frequency signal by using an electrical delay line and / or a phase-locked loop, ensuring that the absolute phase of the target high-frequency signal at the receiving end is consistent with that of the high-frequency reference signal at the transmitting end, eliminating the operation delay introduced during frequency down-conversion and / or frequency multiplication, ensuring strict alignment of polarization state selection and time synchronization in the BB84 protocol, and reducing the bit error rate caused by basis vector misalignment.

[0105] Based on the above method embodiments, this application also provides a low-frequency synchronization signal synchronization device based on the BB84 protocol, which is applied to the transmitter of a quantum communication system. Figure 5 A schematic diagram of the structure of a low-frequency synchronization signal synchronization device based on the BB84 protocol provided in this application embodiment. Figure 1 ,like Figure 5 As shown, the device may include: Signal generation module 310 is used to generate high-frequency reference signals and low-frequency synchronization signals; The encoding generation module 320 is used to trigger the first set of random encoding bases to perform quantum state encoding on the information to be transmitted based on the high-frequency reference signal; The encoding and transmitting module 330 is used to transmit quantum state codes to the receiving end of the quantum communication system based on the frequency of the high-frequency reference signal. The signal synchronization module 340 is used to modulate the low-frequency synchronization signal onto a preset optical carrier and transmit the target optical carrier carrying the low-frequency synchronization signal to the receiving end, so that the receiving end can extract the low-frequency synchronization signal from the target optical carrier. The frequency transmission module 350 is used to transmit the frequency of the high-frequency reference signal to the receiving end, so that the receiving end can perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate the target high-frequency signal, and trigger the second set of random coding basis to decode the quantum state code according to the target high-frequency signal to obtain the decoded information. The first negotiation module 360 ​​is used to negotiate with the receiving end on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information, and to determine the target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitting end and the receiving end, respectively.

[0106] Optionally, the device further includes: The parameter adjustment module is used to obtain the channel state parameters of the quantum channel between the transmitter and receiver; the quantum channel is used to transmit quantum state encoding; and the parameters of the high-frequency reference signal and the low-frequency synchronization signal are adjusted according to the signal state parameters.

[0107] Optionally, the signal generation module 310 is specifically used to generate a first high-frequency signal; reduce the frequency of the first high-frequency signal to generate a low-frequency synchronization signal; and perform delay compensation on the first high-frequency signal based on the delay between the first high-frequency signal and the low-frequency synchronization signal to generate a high-frequency reference signal.

[0108] Based on the above method embodiments, this application also provides a low-frequency synchronization signal synchronization device based on the BB84 protocol, which is applied to the receiving end of a quantum communication system. Figure 6 A schematic diagram of the structure of a low-frequency synchronization signal synchronization device based on the BB84 protocol provided in this application embodiment. Figure 2 ,like Figure 6 As shown, the device may include: Information receiving module 410 is used to acquire the frequency and quantum state encoding of the target optical carrier and high-frequency reference signal sent by the transmitter of the quantum communication system; The frequency conversion module 420 is used to extract the low-frequency synchronization signal from the target optical carrier, and perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate the target high-frequency signal. Decoding module 430 is used to decode the quantum state encoding triggered by the second set of random coding basis according to the target high-frequency signal to obtain the decoded information; The second negotiation module 440 is used to negotiate with the transmitter on the first set of random coding bases, the second set of random coding bases, the information to be sent, and the decoding information, and to determine the target information from the information to be sent and the decoding information. The target information is used to generate quantum keys at the transmitter and the receiver respectively. Among them, the target optical carrier, high-frequency reference signal, quantum state encoding, first set of random encoding basis and information to be transmitted are generated using a device such as that applied to the transmitting end.

[0109] Optionally, the frequency conversion module 420 is specifically used to perform phase-locked loop frequency multiplication on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a second high-frequency signal; and to perform delay compensation on the second high-frequency signal according to the delay between the second high-frequency signal and the low-frequency synchronization signal to generate a target high-frequency signal.

[0110] Optionally, the frequency conversion module 420 is also used to control the electrical delay line based on the delay of the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

[0111] Optionally, the frequency conversion module 420 is also used to control the phase-locked loop based on the delay of the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

[0112] The above-described device is used to execute the method provided in the foregoing embodiments, and its implementation principle and technical effect are similar, so they will not be described again here.

[0113] These modules can be one or more integrated circuits configured to implement the above methods, such as one or more Application Specific Integrated Circuits (ASICs), one or more microprocessors, or one or more Field Programmable Gate Arrays (FPGAs). Alternatively, when a module is implemented using processing element scheduler code, the processing element can be a general-purpose processor, such as a Central Processing Unit (CPU) or other processor capable of calling program code. Furthermore, these modules can be integrated together as a system-on-a-chip (SOC).

[0114] Figure 7 This is a schematic diagram of the terminal device provided in the embodiments of this application, such as... Figure 7 As shown, the terminal device 500 may include a processor 510, a storage medium 520, and a bus. The storage medium 520 stores program instructions executable by the processor 510. When the terminal device 500 is running, the processor 510 communicates with the storage medium 520 via the bus, and the processor 510 executes the program instructions to perform the above-described method embodiment. The specific implementation and technical effects are similar and will not be described in detail here.

[0115] Optionally, this application also provides a computer-readable storage medium storing a computer program, which is executed by a processor to perform the above-described method embodiments.

[0116] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0117] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0118] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in a combination of hardware and software functional units.

[0119] The integrated units implemented as software functional units described above can be stored in a computer-readable storage medium. These software functional units, stored in a storage medium, include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute some steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0120] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A low-frequency synchronization signal synchronization method based on the BB84 protocol, characterized in that, The method, applied to the transmitter of a quantum communication system, includes: Generate a high-frequency reference signal and a low-frequency synchronization signal; The first set of random coding bases is triggered according to the high-frequency reference signal to perform quantum state coding on the information to be transmitted, and the quantum state coding is sent to the receiving end of the quantum communication system. The low-frequency synchronization signal is modulated onto a preset optical carrier, and a target optical carrier carrying the low-frequency synchronization signal is transmitted to the receiving end, so that the receiving end can extract the low-frequency synchronization signal from the target optical carrier. The high-frequency reference signal frequency is sent to the receiving end so that the receiving end performs frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a target high-frequency signal, and triggers a second set of random coding bases to decode the quantum state code according to the target high-frequency signal to obtain decoded information; The receiving end negotiates the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitting end and the receiving end, respectively.

2. The method as described in claim 1, characterized in that, The generation of the high-frequency reference signal and the low-frequency synchronization signal includes: Generate the first high-frequency signal; The first high-frequency signal is down-frequencyd to generate the low-frequency synchronization signal; Based on the delay between the first high-frequency signal and the low-frequency synchronization signal, delay compensation is performed on the first high-frequency signal to generate the high-frequency reference signal.

3. The method as described in claim 1, characterized in that, The method further includes: Obtain the channel state parameters of the quantum channel between the transmitter and the receiver; the quantum channel is used to transmit the quantum state encoding; The parameters of the high-frequency reference signal and the low-frequency synchronization signal are adjusted according to the signal state parameters.

4. A low-frequency synchronization signal synchronization method based on the BB84 protocol, characterized in that, The method, applied to the receiver of a quantum communication system, includes: The frequency and quantum state encoding of the target optical carrier and high-frequency reference signal transmitted by the transmitter of the quantum communication system are obtained. A low-frequency synchronization signal is extracted from the target optical carrier, and the low-frequency synchronization signal is frequency-converted according to the frequency of the high-frequency reference signal to generate a target high-frequency signal; Based on the target high-frequency signal, the second set of random coding bases is triggered to decode the quantum state encoding to obtain the decoded information; The transmitter negotiates with the receiver on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitter and the receiver, respectively. The target optical carrier, the high-frequency reference signal, the quantum state encoding, the first set of random encoding bases, and the information to be transmitted are generated using the method described in any one of claims 1-3.

5. The method as described in claim 4, characterized in that, The step of frequency conversion of the low-frequency synchronization signal based on the frequency of the high-frequency reference signal to generate the target high-frequency signal includes: Based on the frequency of the high-frequency reference signal, the low-frequency synchronization signal is subjected to phase-locked loop frequency multiplication to generate a second high-frequency signal; Based on the delay between the second high-frequency signal and the low-frequency synchronization signal, delay compensation is performed on the second high-frequency signal to generate the target high-frequency signal.

6. The method as described in claim 5, characterized in that, The step of performing delay compensation on the second high-frequency signal based on the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal includes: The electrical delay line is controlled based on the delay of the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

7. The method as described in claim 5 or 6, characterized in that, The step of performing delay compensation on the second high-frequency signal based on the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal includes: The phase-locked loop is controlled based on the delay between the second high-frequency signal and the low-frequency synchronization signal to generate the target high-frequency signal.

8. A low-frequency synchronization signal synchronization device based on the BB84 protocol, characterized in that, The device, used as a transmitter in a quantum communication system, includes: The signal generation module is used to generate high-frequency reference signals and low-frequency synchronization signals; The encoding processing module is used to trigger the first set of random encoding bases to perform quantum state encoding on the information to be transmitted based on the high-frequency reference signal, and to send the quantum state encoding to the receiving end of the quantum communication system; A signal synchronization module is used to modulate the low-frequency synchronization signal onto a preset optical carrier and transmit the target optical carrier carrying the low-frequency synchronization signal to the receiving end, so that the receiving end can extract the low-frequency synchronization signal from the target optical carrier. The frequency transmission module is used to transmit the frequency of the high-frequency reference signal to the receiving end, so that the receiving end can perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a target high-frequency signal, and trigger a second set of random coding bases to decode the quantum state code according to the target high-frequency signal to obtain decoded information. The first negotiation module is used to negotiate with the receiving end on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information, and to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitting end and the receiving end, respectively.

9. A low-frequency synchronization signal synchronization device based on the BB84 protocol, characterized in that, The device, used as a receiver in a quantum communication system, includes: The information receiving module is used to acquire the frequency and quantum state encoding of the target optical carrier and high-frequency reference signal transmitted by the transmitter of the quantum communication system. The frequency conversion module is used to extract a low-frequency synchronization signal from the target optical carrier, and perform frequency conversion on the low-frequency synchronization signal according to the frequency of the high-frequency reference signal to generate a target high-frequency signal. The decoding module is used to decode the quantum state encoding based on the target high-frequency signal triggering the second set of random coding bases to obtain decoded information; The second negotiation module is used to negotiate with the transmitter on the first set of random coding bases, the second set of random coding bases, the information to be transmitted, and the decoding information, and to determine target information from the information to be transmitted and the decoding information. The target information is used to generate quantum keys at the transmitter and the receiver respectively. The target optical carrier, the high-frequency reference signal, the quantum state encoding, the first set of random encoding bases, and the information to be transmitted are generated using the apparatus described in claim 8.

10. A terminal device, characterized in that, include: The device includes a processor, a storage medium, and a bus. The storage medium stores program instructions executable by the processor. When the terminal device is running, the processor communicates with the storage medium via the bus. The processor executes the program instructions to perform the steps of the low-frequency synchronization signal synchronization method as described in any one of claims 1 to 3, or the steps of the low-frequency synchronization signal synchronization method as described in any one of claims 4 to 7.

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