A microwave continuous-variable quantum key distribution method and system

Abstract

The application discloses a microwave continuous variable quantum key distribution method and system, and relates to the technical field of quantum key distribution. The method comprises the following steps: a transmitting end performs Gaussian modulation on a coherent state of a microwave frequency, and couples the Gaussian modulation coherent state into a free space quantum channel; a receiving end performs homodyne detection on the received Gaussian modulation coherent state, and obtains a canonical component; the receiving end broadcasts a detection basis of each Gaussian modulation coherent state on an authenticated classical channel, the transmitting end retains the canonical component corresponding to the same detection basis as the receiving end, and determines N pairs of original keys according to the retained canonical component and the canonical component obtained by the receiving end; then, the N pairs of original keys are segmented into small blocks with a fixed size, and an isolation forest algorithm is used to remove abnormal small blocks in all the small blocks; and finally, both communication parties perform a post-processing protocol on the remaining small blocks through the classical channel, and obtain a secure key. The method solves the problem of short communication distance of microwave CV-QKD in the prior art.

Description

Technical Field

[0001] This invention relates to the field of quantum key distribution technology, and in particular to a microwave continuous variable quantum key distribution method and system. Background Technology

[0002] Quantum key distribution (QKD) is a type of quantum communication technology that uses the quantum states of particles to encode information for transmission, ensuring the security of information transmission. Due to the physical properties of quantum mechanics, quantum communication is unconditionally secure. Continuous variable quantum key distribution (CV-QKD) is a type of QKD. CV-QKD schemes emit electromagnetic waves; they typically utilize continuous variables of light, such as phase or amplitude, to encode key bits.

[0003] In the field of quantum key distribution, the microwave frequency band has unique advantages. It can utilize existing microwave communication technologies and equipment, and in some cases, compared to optical frequency bands, microwaves may be less affected by environmental factors during transmission and have better penetration. Depending on the transmission medium, CV-QKD can be divided into two types: fiber-channel QKD and free-space QKD. Free-space QKD uses space as the transmission medium and is more versatile and flexible in network deployment compared to fiber-channel QKD.

[0004] However, microwave CV-QKD faces limitations in practical applications due to noise, including free-space channel noise, end-measurement noise, and noise introduced by attacks. This noise affects the quantum signal propagating through the atmosphere in free-space QKD, making it difficult to achieve long-distance key sharing. Summary of the Invention

[0005] Based on this, it is necessary to provide a microwave continuous variable quantum key distribution method and system to address the above-mentioned technical problems. This method solves the problem of short communication distance in existing microwave CV-QKD technologies.

[0006] The present invention adopts the following technical solution: This invention provides a microwave continuous-variable quantum key distribution method, applied to a microwave continuous-variable quantum key distribution system, the system including a transmitter and a receiver; the method includes: The transmitter generates a dual-mode compressed state, processes the dual-mode compressed state to obtain a Gaussian-modulated coherent state at microwave frequency, and couples the Gaussian-modulated coherent state into a free-space quantum channel; the Gaussian-modulated coherent state includes two canonical components, specifically an amplitude component and a phase component; The receiver receives the Gaussian modulated coherent state transmitted by the transmitter and performs zero-difference detection on the received Gaussian modulated coherent state through a random detection basis to obtain a regular component; this regular component is either an amplitude component or a phase component. The receiver broadcasts the detection basis of each Gaussian modulated coherent state on the authenticated classical channel and couples the obtained regularized component into the free space quantum channel. The transmitter retains the regularized component corresponding to the same detection basis as the receiver and determines N pairs of original keys based on the retained regularized component and the regularized component obtained by the receiver. The transmitting end divides the N pairs of original keys into fixed-size blocks and uses the isolated forest algorithm to remove abnormal blocks from all blocks; The transmitter and receiver perform a post-processing protocol on the remaining small blocks on the authenticated classic channel to obtain the security key.

[0007] Optionally, the transmitter includes a traveling-wave parametric amplifier and a microwave signal heterodyne detector. The transmitter generates a dual-mode compressed state and processes the dual-mode compressed state to obtain a Gaussian-modulated coherent state at the microwave frequency, including: A two-mode compressed state with a preset variance is prepared at a preset temperature using a traveling wave parametric amplifier; A heterodyne measurement is applied to one mode of a dual-mode compressed state using a microwave signal heterodyne detector to project the other mode as a Gaussian-modulated coherent state at microwave frequency.

[0008] Optionally, the transmitter also includes a first microwave antenna to couple the Gaussian-modulated coherent state into the free-space quantum channel, including: The Gaussian-modulated coherent state is coupled into the free-space quantum channel via a first microwave antenna.

[0009] Optionally, the receiver includes a second microwave antenna and a microwave signal homodyne detector; the receiver receives the Gaussian modulated coherent state transmitted by the transmitter, and performs homodyne detection on the received Gaussian modulated coherent state using a random detection basis to obtain a canonical component, including: The Gaussian modulated coherent state transmitted by the transmitter is received by the second microwave antenna, and the received Gaussian modulated coherent state is detected by a microwave signal null detector at a preset temperature through a random detection basis to obtain the canonical component.

[0010] Optionally, N pairs of original keys are , x represents the number of regularized components corresponding to the same detection basis at the receiver. i express The regularized component corresponding to the i-th detection basis that is the same as that of the receiver. This represents the regularized component corresponding to the i-th detection basis at the receiver that is the same as that at the transmitter.

[0011] Optionally, the N pairs of original keys are divided into fixed-size blocks, including: Based on a predefined block size k, the N pairs of original keys are divided into R blocks to obtain the dataset. For the dataset, each small block of dataset M is... Each element in the small block consists of two parts, represented as ,in, This indicates the channel response.

[0012] Optionally, the Isolation Forest algorithm is used to remove outlier blocks from all blocks, including: according to Construct an isolated forest and calculate the outlier score for each small patch based on the isolated forest; Normalize the outlier scores of all small blocks; Remove small blocks whose abnormal scores exceed the outlier threshold.

[0013] Optionally, according to Constructing isolated forests includes: from Random selection For each sample, an isolation tree is constructed by recursively partitioning the samples, and the constructed isolation tree is added to the isolation forest; If the number of isolated trees in the isolated forest is less than the preset number of isolated trees, continue execution from... Random selection For each sample, an isolation tree is constructed by recursively dividing the sample and adding the constructed isolation tree to the isolation forest. This process continues until the number of isolation trees in the isolation forest is greater than or equal to the preset number of isolation trees, thus obtaining the constructed isolation forest.

[0014] Optionally, an anomaly score is calculated for each small block, including: For any given small block, calculate the average height of all isolated trees in the isolated forest for each data point in the small block; Calculate the outlier value for each data point in the small block based on the average height; The mean of the outliers among all data points in a small block is determined as the outlier score of the small block.

[0015] This invention provides a microwave continuous variable quantum key distribution system, which includes a transmitter and a receiver. The transmitter includes a traveling wave parametric amplifier, a microwave signal heterodyne detector, a first microwave antenna, and a first processing unit. The receiver includes a second microwave antenna, a microwave signal homodyne detector, and a second processing unit. Traveling wave parametric amplifier, used to generate two-mode compressed states; A microwave signal heterodyne detector is used to process the dual-mode compressed state to obtain a Gaussian-modulated coherent state at the microwave frequency; the Gaussian-modulated coherent state includes two canonical components, specifically an amplitude component and a phase component; The first microwave antenna is used to couple a Gaussian-modulated coherent state to a free-space quantum channel; The second microwave antenna is used to receive the Gaussian modulated coherent state transmitted by the transmitter. A microwave signal zero-difference detector is used to perform zero-difference detection on the received Gaussian modulated coherent state through a random detection basis to obtain a canonical component; the canonical component is either an amplitude component or a phase component. The second microwave antenna at the receiver broadcasts the detection basis of each Gaussian modulated coherent state on the certified classical channel and couples the obtained regularized components into the free-space quantum channel. The first processing unit at the transmitter retains the regularized components corresponding to the same detection basis as the receiver and determines N pairs of original keys based on the retained regularized components and the regularized components obtained at the receiver. The first processing unit divides the N pairs of original keys into small blocks of fixed size and uses the isolated forest algorithm to remove abnormal blocks from all blocks. The first processing unit and the second processing unit perform a post-processing protocol through the certified classical channel to obtain the security key.

[0016] The present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described microwave continuous-variable quantum key distribution method.

[0017] The present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described microwave continuous variable quantum key distribution method.

[0018] The above-mentioned at least one technical solution adopted in this invention can achieve the following beneficial effects: In the microwave continuous-variable quantum key distribution method of this invention, the transmitter prepares a dual-mode compressed state and processes it into a Gaussian-modulated coherent state at microwave frequency; the receiver receives the Gaussian-modulated coherent state at microwave frequency and performs zero-difference detection on it using a random detection basis to obtain a regularized component; this regularized component is either an amplitude component or a phase component, and the type of regularized component corresponding to different detection bases is different. Then, the detection basis of each Gaussian-modulated coherent state is broadcast through a classical channel. The transmitter retains the regularized component corresponding to the same detection basis as the receiver, and determines N pairs of original keys based on the regularized component retained by the transmitter and the regularized component obtained by the receiver; the transmitter divides the key bits into small blocks of fixed size and uses the isolated forest algorithm to remove abnormal small blocks; the two communicating parties cooperate through a post-processing protocol via a classical channel to obtain the final secure key; this method combines microwave CV-QKD with the isolated forest algorithm, which can efficiently and accurately filter abnormal keys, eliminate noise such as measurement noise and free-space channel noise, overcome the limitation of communication distance by noise, and improve the transmission distance of the microwave CV-QKD system. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 A schematic diagram of a microwave continuous variable quantum key distribution method provided by the present invention; Figure 2 This is a schematic diagram illustrating the outlier detection method using an isolated forest algorithm. Figure 3 This is a schematic diagram illustrating anomaly detection of keys using an isolated forest algorithm. Figure 4 This is a comparison chart showing whether the key rate of a microwave CV-QKD method is used under different modulation variances. Figure 5 A schematic diagram of a computer device for implementing a microwave continuous variable quantum key distribution method provided by the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] CV-QKD and Discrete Variable Quantum Key Distribution (DV-QKD) are two different types of QKD. CV-QKD schemes emit electromagnetic waves and typically use continuous variables of light, such as phase or amplitude, to encode key bits. DV-QKD schemes emit discrete variable quantum particles and typically use discrete properties of photons, such as the polarization state of auroras, to encode key bits. Compared to DV-QKD, CV-QKD transmits multiple bits within a time period, achieving high key transmission rates. Furthermore, CV-QKD is well-reintegrated with traditional optical communication technologies and can be readily combined with existing classical optical communication network systems. Based on the transmission medium, CV-QKD can be divided into two types: fiber-channel QKD and free-space QKD. Free-space QKD uses space as the transmission medium, making it more versatile and flexible in network deployment compared to fiber-channel QKD. However, environmental conditions, such as atmospheric absorption, scattering, and weather events like rain and snow, can affect the quantum signals propagating through the atmosphere in free-space QKD. Studies have shown that these environmental effects vary depending on the wavelength of the signal, with longer wavelength microwaves being less affected than shorter wavelength light waves. Therefore, microwave CV-QKD systems have become a prominent research area.

[0023] Anomaly detection is an important branch of machine learning, aiming to identify anomalous data that is significantly different from normal data from large datasets. Isolation Forest is an unsupervised anomaly detection algorithm based on machine learning. It recursively and randomly partitions the dataset until each dataset is isolated, similar to decision trees and random forests. Because anomalous attribute values ​​are more easily separated, anomalous data is closer to the root node, while normal data is farther away. Isolation Forest has been widely used in various fields due to its advantages such as requiring no labeled data, low linear time complexity, and good detection performance.

[0024] However, in the field of microwave continuous-variable quantum key distribution (CV-QKD), there is no precedent for applying the isolated forest algorithm to key screening. In quantum key distribution, anomalies represent data that is heavily affected by noise. Causes of anomalies include channel noise, measurement noise, and noise introduced by attacks. Microwave CV-QKD faces noise limitations in practical applications, making long-distance key sharing difficult. Traditional key screening methods relying on digital signal processing techniques have limited efficiency and accuracy. A performance enhancement scheme for microwave CV-QKD systems based on machine learning methods can efficiently and accurately filter anomalous keys, overcome the noise limitation on communication distance, and improve system performance.

[0025] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] In one embodiment, the present invention provides a microwave continuous variable quantum key distribution system, the system comprising a transmitter and a receiver; the transmitter comprises a traveling wave parametric amplifier, a microwave signal heterodyne detector, a first microwave antenna and a first processing unit, and the receiver comprises a second microwave antenna, a microwave signal homodyne detector and a second processing unit.

[0027] Traveling wave parametric amplifier, used to generate two-mode compressed states.

[0028] A microwave signal heterodyne detector is used to process the dual-mode compressed state to obtain a Gaussian-modulated coherent state at the microwave frequency. The Gaussian-modulated coherent state includes two canonical components, specifically an amplitude component and a phase component.

[0029] Among them, the Gaussian modulated coherent state at microwave frequency is the microwave quantum state. ,in, For amplitude components, For regular components, It is an imaginary number.

[0030] The first microwave antenna is used to couple a Gaussian-modulated coherent state to a free quantum channel.

[0031] The second microwave antenna is used to receive the Gaussian modulated coherent state transmitted by the transmitter.

[0032] A microwave signal zero-difference detector is used to perform zero-difference detection on the received Gaussian modulated coherent state through a random detection basis to obtain a canonical component; the canonical component is either an amplitude component or a phase component.

[0033] The second microwave antenna at the receiver broadcasts the detection basis of each Gaussian modulated coherent state on the certified classical channel and couples the obtained regularized components into the free-space quantum channel. The first processing unit at the transmitter retains the regularized components corresponding to the same detection basis as the receiver and determines N pairs of original keys based on the retained regularized components and the regularized components obtained at the receiver. The first processing unit divides the N pairs of original keys into small blocks of fixed size and uses the isolated forest algorithm to remove abnormal blocks from all blocks. The first processing unit and the second processing unit perform a post-processing protocol through the certified classical channel to obtain the security key.

[0034] Specifically, the traveling wave parametric amplifier is basically composed of a superconducting nonlinear asymmetric inductive element (SNAIL) unit. The superconducting nonlinear asymmetric inductive element unit, which operates in a low-temperature environment, is driven by a strong microwave pump signal to generate a two-mode squeezed state (TMS state), namely the Einstein-Podolsky-Rosen state (EPR state).

[0035] Microwave signal heterodyne detectors detect canonical components in quantum states at low temperatures. , .

[0036] The first microwave antenna can be modeled as a transmission line whose impedance varies with space, connecting 50 Traveling wave parametric amplifier in low temperature environment and A room-temperature free-space quantum channel couples microwave quantum states generated in a low-temperature environment to a room-temperature free-space quantum channel and transmits them to the receiver; the gain of the first microwave antenna... ,in, Radiation efficiency is used to represent antenna loss, and D represents antenna directivity, which indicates the antenna's ability to focus transmitted power in a specific direction. , Indicates the signal wavelength. A represents the aperture efficiency, which is determined by the size and shape of the antenna. The gain effect of microwave antennas can alleviate the path loss of quantum states in the channel.

[0037] The second microwave antenna receives Gaussian-modulated coherent states in a free-space quantum channel.

[0038] A microwave signal homodyne detector converts quantum signals into electrical signals by measuring the phase difference between the received Gaussian modulated coherent state and the local oscillator under low-temperature conditions. Microwave homodyne detection includes a signal amplification stage and a signal detection stage. In the signal amplification stage, the received signal mode is amplified by a phase-insensitive linear amplifier G, a process that introduces amplification noise. In the signal detection stage, the amplified microwave signal and the local oscillator signal LO are down-converted through a microwave frequency mixer to generate two signals. This stage introduces mixed noise. Finally, the output signal is sampled using an analog-to-digital converter (ADC) to complete the signal measurement and obtain the regular component.

[0039] Based on the aforementioned microwave continuous-variable quantum key distribution system, this invention also provides a microwave continuous-variable quantum key distribution method, which is applied to the microwave continuous-variable quantum key distribution system; such as Figure 1 As shown, Figure 1 This is a schematic diagram of a microwave continuous-variable quantum key distribution method according to the present invention, which specifically includes the following steps: S101, the transmitter generates a dual-mode compressed state, processes the dual-mode compressed state to obtain a Gaussian modulated coherent state at microwave frequency, and couples the Gaussian modulated coherent state into the free space quantum channel; the Gaussian modulated coherent state includes two canonical components, specifically an amplitude component and a phase component.

[0040] The transmitter generates a dual-mode compressed state and processes it to obtain a Gaussian-modulated coherent state at microwave frequency. This process includes: preparing a dual-mode compressed state with a preset variance at a preset temperature using a traveling-wave parametric amplifier; applying a heterodyne measurement to one mode of the dual-mode compressed state using a microwave signal heterodyne detector to project the other mode into a Gaussian-modulated coherent state at microwave frequency; the Gaussian-modulated coherent state is the microwave quantum state.

[0041] The preset temperature is T = 20 mK.

[0042] Specifically, it includes the following steps: S11, the transmitter uses a traveling-wave parametric amplifier to prepare a two-mode compressed state with variance V in a low-temperature environment (T = 20 mK). Its initial state consists of mode A and mode B. Composition, covariance matrix of the two-mode compressed state for: (1); in, Let A be the covariance matrix of mode A. Representing mode A and mode B The correlation matrix between them Representing modes The covariance matrix, ; .

[0043] S12, The transmitting end uses a microwave signal heterodyne detector to obtain the detection result by applying heterodyne measurement to mode A. .in, This represents the amplitude component of mode A. This represents the phase component of mode A.

[0044] S13, by using heterodyne detection to determine the transformation relationship between the first and second-order statistics of the Gaussian state, the mode can be determined. The coherent state can be represented as: (2); (3); in, This represents the displacement vector of mode B0, and also represents the canonical component of mode B0. .

[0045] S14, utilizing Known modes The variance of the displacement vector projected onto the coherent state is equal to the modulation variance.

[0046] In one embodiment, the transmitter further includes a first microwave antenna for coupling the Gaussian-modulated coherent state to the free-space quantum channel, including: coupling the Gaussian-modulated coherent state to the free-space quantum channel through the first microwave antenna.

[0047] S102, the receiver receives the Gaussian modulated coherent state transmitted by the transmitter, and performs zero-difference detection on the received Gaussian modulated coherent state through a random detection basis to obtain a regular component; the regular component is an amplitude component or a phase component.

[0048] In one embodiment, the receiver includes a second microwave antenna and a microwave signal homodyne detector; the receiver receives the Gaussian modulated coherent state transmitted by the transmitter, and performs homodyne detection on the received Gaussian modulated coherent state using a random detection basis to obtain a canonical component, including: The Gaussian modulated coherent state transmitted by the transmitter is received by the second microwave antenna, and the received Gaussian modulated coherent state is detected by a microwave signal null detector at a preset temperature through a random detection basis to obtain the canonical component.

[0049] By using a microwave signal null detector at a preset temperature to perform null detection on the received Gaussian modulated coherent state through a random detection basis, the canonical component can be obtained.

[0050] A microwave signal homodyne detector performs homodyne detection on the received Gaussian modulated coherent state, measuring X or P quadrature to obtain the measurement result (canonical component). Specifically, the receiver generates a binary random number with equal probability. ,when When the receiver performs amplitude orthogonal detection, the obtained canonical component is the amplitude component; conversely, if... This is phase orthogonal detection, and the obtained regular component is the phase component. The preset temperature is a low-temperature environment, with a preset temperature of T = 20 mK.

[0051] Specifically, the microwave quantum state in the free quantum channel is received by the second microwave antenna at the receiving end.

[0052] S103, the receiver broadcasts the detection basis of each Gaussian modulated coherent state on the authenticated classical channel and couples the obtained regularized component into the free space quantum channel. The transmitter retains the regularized component corresponding to the same detection basis as the receiver and determines N pairs of original keys based on the retained regularized component and the regularized component obtained by the receiver.

[0053] Each Gaussian modulated coherent state at the transmitter includes two canonical components: an amplitude component and a phase component. The receiver obtains the amplitude component or quadrature component through a random detection basis. The receiver publishes the detection basis used to detect each Gaussian modulated coherent state to the transmitter. The transmitter retains the canonical component corresponding to the same detection basis as the receiver. For example, if the receiver uses amplitude quadrature detection, the transmitter retains the amplitude component and deletes the phase component; if the receiver uses phase quadrature detection, the transmitter retains the phase component and deletes the amplitude component.

[0054] The regularized components retained at the transmitting end and those generated at the receiving end are combined to generate N pairs of original keys. Optionally, N pairs of original keys... , x represents the number of regularized components corresponding to the same detection basis at the receiver. i express The regularized component corresponding to the i-th detection basis that is the same as that of the receiver. This represents the regularized component corresponding to the i-th detection basis at the receiver that is the same as that at the transmitter.

[0055] , include , include ,in, , It's transmittance. Where L is the attenuation coefficient and L is the transmission distance; It follows a central normal distribution with variance of . , Excessive noise; the random variable x follows a pattern with a mean of 0 and a variance of . It follows a normal distribution.

[0056] S104, the transmitter divides the N pairs of original keys into small blocks of fixed size and uses the isolated forest algorithm to remove abnormal blocks from all the blocks.

[0057] Optionally, the N pairs of original keys are divided into fixed-size blocks, including: dividing the N pairs of original keys into R blocks according to a predefined block size k, to obtain the dataset. Each small block of dataset M is Each element in the small block consists of two parts, represented as ,in, Indicates the channel response; .

[0058] In one embodiment, the isolation forest algorithm is used to remove outlier blocks from all blocks, including: based on Construct an isolated forest and calculate the outlier score for each patch based on the isolated forest; normalize the outlier scores of all patches; remove patches whose outlier scores are higher than the outlier score threshold.

[0059] The outlier score threshold can be set according to requirements.

[0060] Specifically, according to Constructing isolated forests includes: from Random selection For each sample, an isolation tree is constructed by recursively partitioning the samples, and the constructed isolation tree is added to the isolation forest; if the number of isolation trees in the isolation forest is less than the preset number of isolation trees, the process continues from... Random selection For each sample, an isolation tree is constructed by recursively dividing the sample and adding the constructed isolation tree to the isolation forest. This process continues until the number of isolation trees in the isolation forest is greater than or equal to the preset number of isolation trees, thus obtaining the constructed isolation forest.

[0061] Among them, the depth of the isolation tree For log2 ,from The number of randomly selected samples is the sampling size used to construct the isolation tree.

[0062] Specifically, from the dataset Random selection For each sample, an isolation tree is constructed by recursively partitioning the sample set until all samples belonging to it are isolated. Finally, the constructed isolation tree Add to isolated forest In the middle, until the isolated forest The number of isolation trees in the middle reaches the number of isolation trees Q.

[0063] In one embodiment, calculating the outlier score for each block includes: for any given block, calculating the average height of each data point in the block across all isolated trees in the isolated forest; calculating the outlier value for each data point in the block based on the average height; and determining the mean of the outlier values ​​for all data points in the block as the outlier score for the block.

[0064] Specifically, calculate the data points in the small block. In the isolated forest The average height in is expressed as ,in Representing data points In the isolation tree The height.

[0065] Calculate data points outliers The range of values ​​is The closer the outlier value is to 1, the more likely that the point is an outlier.

[0066] (4) in, This indicates the number of samples used to construct the isolation tree. Representing data points Outliers, Representing data points The average height of all the isolated trees in the isolated forest, Indicates the number of samples is The average path length of unsuccessful searches. Harmonic number, .

[0067] S105, the transmitter and receiver perform a post-processing protocol on the remaining small blocks on the authenticated classic channel to obtain the security key.

[0068] Post-processing mainly includes error correction and privacy amplification. Error correction can use the Cascade protocol and LDPC codes (low-density parity-check codes), while privacy amplification can use Toeplitz hashing and Universal Hashing. Post-processing ensures that both communicating parties obtain a completely consistent and absolutely secure key.

[0069] In one embodiment, the present invention also provides a microwave continuous-variable quantum key distribution method, the method comprising the following steps: S1, the transmitter uses a traveling-wave parametric amplifier to prepare a dual-mode compressed state with variance V in a low-temperature environment, and uses a microwave signal heterodyne detector to apply heterodyne measurement to one mode A to transmit the other mode. The projection is a microwave quantum state.

[0070] S2, the transmitting end uses a microwave antenna to couple the microwave quantum state in the low-temperature environment prepared in S1 to the free space quantum channel.

[0071] S3, the receiver receives the microwave quantum state through a microwave antenna and uses a microwave signal zero-difference detector to detect it in a low-temperature environment to obtain the canonical component.

[0072] S4, the receiver broadcasts the detection basis for each microwave quantum state through a classical channel. The transmitter, based on the detection basis published by the receiver, removes the canonical components of microwave quantum states with different detection bases from the receiver's. Based on the canonical components retained by the transmitter and the canonical components obtained by the receiver, N pairs of original keys are determined. .

[0073] S5, the transmitter divides the key bits into small blocks of fixed size and uses the Isolation Forest algorithm to remove obvious abnormal blocks.

[0074] S6: The two communicating parties cooperate through a post-processing protocol using a classic channel to obtain the final security key.

[0075] In one embodiment, such as Figures 2-4 As shown, Figure 2 This is a schematic diagram of an isolated forest algorithm for detecting outliers. By detecting random points, the anomaly detection capability of the isolated forest algorithm is demonstrated. Figure 3 This diagram illustrates the key anomaly detection method of the Isolation Forest algorithm, where the horizontal axis represents the receiver key and the vertical axis represents the channel response, demonstrating the key filtering effect of the Isolation Forest algorithm. Figure 4 This is a comparison graph showing the key rate of a microwave CV-QKD under different modulation variances with and without the use of this method. The horizontal axis represents the communication distance, and the vertical axis represents the key rate. Using this method allows communication over longer distances, and at the same distance, it achieves a higher key rate, demonstrating the improvement of CV-QKD performance by this method.

[0076] A key metric for evaluating the performance of quantum key distribution is the relationship between the key rate and the distance; the key rate must be greater than zero. As shown in the figure, the key rate is improved when using this invention under different modulation variances.

[0077] The microwave continuous-variable quantum key distribution method provided by this invention reduces the impact of environmental conditions on quantum signals by using microwave continuous quantum key distribution in a free-space quantum channel; and improves the transmission distance and system performance of the microwave CV-QKD system by using the isolated forest algorithm to efficiently and accurately screen anomalous keys.

[0078] When applying the microwave continuous variable quantum key distribution method provided by this invention, it is not necessary to... Figure 1 The steps shown are executed in sequence. The specific execution order of each step can be determined as needed, and this invention does not impose any restrictions on it.

[0079] The present invention also provides a computer-readable storage medium storing a computer program that can be used to execute the above-described... Figure 1A microwave continuous-variable quantum key distribution method is provided.

[0080] The present invention also provides Figure 5 The schematic diagram of the computer device shown is as follows: Figure 5 As shown, at the hardware level, this computer device includes a processor, internal bus, network interface, memory, and non-volatile memory, and may also include other hardware required for business operations. The processor reads the corresponding computer program from the non-volatile memory into memory and then executes it to achieve the above. Figure 1 A microwave continuous-variable quantum key distribution method is provided.

[0081] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this invention.

Claims

1. A method of microwave continuous-variable quantum key distribution, characterized by, A method for applying a microwave continuous-variable quantum key distribution system, the system comprising a transmitter and a receiver, includes: The transmitter generates a dual-mode compressed state, processes the dual-mode compressed state to obtain a Gaussian-modulated coherent state at microwave frequency, and couples the Gaussian-modulated coherent state into a free-space quantum channel; the Gaussian-modulated coherent state includes two canonical components, specifically an amplitude component and a phase component; The receiver receives the Gaussian modulated coherent state transmitted by the transmitter and performs zero-difference detection on the received Gaussian modulated coherent state through a random detection basis to obtain a regular component; this regular component is either an amplitude component or a phase component. The receiver broadcasts the detection basis of each Gaussian modulated coherent state on the authenticated classical channel and couples the obtained regularized component into the free space quantum channel. The transmitter retains the regularized component corresponding to the same detection basis as the receiver and determines N pairs of original keys based on the retained regularized component and the regularized component obtained by the receiver. The transmitting end divides the N pairs of original keys into fixed-size blocks and uses the isolated forest algorithm to remove abnormal blocks from all blocks; The transmitter and receiver perform a post-processing protocol on the remaining small blocks on the authenticated classic channel to obtain the security key.

2. The method of claim 1, wherein, The transmitter includes a traveling-wave parametric amplifier and a microwave signal heterodyne detector. The transmitter generates a dual-mode compressed state and processes it to obtain a Gaussian-modulated coherent state at the microwave frequency, including: A two-mode compressed state with a preset variance is prepared at a preset temperature using a traveling wave parametric amplifier; A heterodyne measurement is applied to one mode of a dual-mode compressed state using a microwave signal heterodyne detector to project the other mode as a Gaussian-modulated coherent state at microwave frequency.

3. The method of claim 1, wherein, The transmitter also includes a first microwave antenna that couples the Gaussian-modulated coherent state into the free-space quantum channel, including: The Gaussian-modulated coherent state is coupled into the free-space quantum channel via a first microwave antenna.

4. The method of claim 1, wherein, The receiver includes a second microwave antenna and a microwave signal homodyne detector; the receiver receives the Gaussian modulated coherent state transmitted by the transmitter, and performs homodyne detection on the received Gaussian modulated coherent state using a random detection basis to obtain the canonical components, including: The Gaussian modulated coherent state transmitted by the transmitter is received by the second microwave antenna, and the received Gaussian modulated coherent state is detected by a microwave signal null detector at a preset temperature through a random detection basis to obtain the canonical component.

5. The method of claim 1, wherein, N pairs of original keys are N is the number of regularized components corresponding to the same detection basis at the receiver, x i This represents the regularized component corresponding to the i-th detection basis at the transmitter that is identical to that at the receiver. This represents the regularized component corresponding to the i-th detection basis at the receiver that is the same as that at the transmitter.

6. The method of claim 5, wherein, Divide the N pairs of original keys into fixed-size blocks, including: According to a predefined small block size k, N pairs of original keys are divided into R small blocks, obtaining a data set Each small block of the data set M is Each element in the small block is composed of two parts, denoted as wherein, denotes a channel response.

7. The method of claim 6, wherein, The Isolation Forest algorithm is used to remove outlier blocks from all smaller blocks, including: According to An isolated forest is constructed, and according to the isolated forest, an anomaly score of each small block is calculated; Normalize the outlier scores of all small blocks; Remove small blocks whose abnormal scores exceed the outlier threshold.

8. The method of claim 7, wherein, According to Constructing an isolated forest, comprising: From randomly select samples, construct an isolation tree by recursively dividing the samples, and add the constructed isolation tree to the isolation forest; In a case where the number of isolated trees in the isolated forest is less than the preset number of isolated trees, continue to perform the operation of randomly selecting samples from the data set, constructing isolated trees by recursively dividing the samples, and adding the constructed isolated trees to the isolated forest, until the number of isolated trees in the isolated forest is greater than or equal to the preset number of isolated trees, to obtain the constructed isolated forest. In a case where the number of isolated trees in the isolated forest is less than the preset number of isolated trees, continue to perform the operation of randomly selecting samples from the data set, constructing isolated trees by recursively dividing the samples, and adding the constructed isolated trees to the isolated forest, until the number of isolated trees in the isolated forest is greater than or equal to the preset number of isolated trees, to obtain the constructed isolated forest.​ 9. The method of claim 7, wherein, Calculate the anomaly score for each small block, including: For any given small block, calculate the average height of all isolated trees in the isolated forest for each data point in the small block; Calculate the outlier value for each data point in the small block based on the average height; The mean of the outliers among all data points in a small block is determined as the outlier score of the small block.

10. A microwave continuous-variable quantum key distribution system, characterized by, The system includes a transmitter and a receiver; the transmitter includes a traveling wave parametric amplifier, a microwave signal heterodyne detector, a first microwave antenna and a first processing unit, and the receiver includes a second microwave antenna, a microwave signal homodyne detector and a second processing unit. Traveling wave parametric amplifier, used to generate two-mode compressed states; A microwave signal heterodyne detector is used to process the dual-mode compressed state to obtain a Gaussian-modulated coherent state at the microwave frequency; the Gaussian-modulated coherent state includes two canonical components, specifically an amplitude component and a phase component; The first microwave antenna is used to couple a Gaussian-modulated coherent state into a free-space quantum channel; The second microwave antenna is used to receive the Gaussian modulated coherent state transmitted by the transmitter. A microwave signal zero-difference detector is used to perform zero-difference detection on the received Gaussian modulated coherent state through a random detection basis to obtain a canonical component; the canonical component is either an amplitude component or a phase component. The receiver's second microwave antenna broadcasts the detection basis of each Gaussian-modulated coherent state on a certified classical channel and couples the resulting canonical component into a free-space quantum channel; The first processing unit of the transmitter retains the regularized component corresponding to the same detection basis as the receiver, and determines N pairs of original keys based on the retained regularized component and the regularized component obtained by the receiver. The N pairs of original keys are divided into small blocks of fixed size, and the isolated forest algorithm is used to remove abnormal small blocks in all small blocks. The first and second processing units perform post-processing protocols on the remaining small blocks on the authenticated classic channel to obtain the security key.

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