Continuous variable quantum key distribution method, device and system

Abstract

The invention discloses a continuous variable quantum key distribution method, device and system, and belongs to the field of wireless communication. Firstly, a sending end generates continuous light pulses for discrete coding, a one-dimensional discrete modulation signal is generated, quantum signal light is generated through an attenuator, and the quantum signal light is coupled to a quantum channel for transmission. Then, a receiving end adopts a homodyne detector to measure the regular component of the quantum signal in a self-calibration manner; and after a local measurement base direction and a phase drift angle introduced by a dynamic compensation quantum channel are adjusted in real time, a covariance matrix is calculated and input into a post-processing module, the code rate of the system is further calculated, and a security key is generated by using a protocol between a receiving end and a transmitting end. According to the device, the intensity modulator is connected between the laser and the attenuator, so that one-dimensional discrete modulation is realized, and dependence on a phase reference signal is avoided. According to the system, a traditional phase locking module is removed, an asymmetric phase space coding mechanism is adopted, dependence on a phase reference signal is eliminated, and the safety and stability of the system are improved.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication, and specifically relates to a continuous variable quantum key distribution method, device, and system. Background Art

[0002] As a frontier field of the cross-integration of quantum physics and information science, quantum secure communication technology has made remarkable progress in both theoretical research and practical applications in recent years.

[0003] Quantum key distribution (QKD) technology, as the core of quantum secure communication, uses the principles of quantum mechanics to ensure the security of key distribution and provides unprecedented security for information transmission. Among them, continuous variable quantum key distribution (CV-QKD) has become a research hotspot in the field of quantum secure communication due to its advantages such as easy integration with traditional optical networks and high key generation rate at short distances.

[0004] However, the current continuous variable quantum key distribution methods still face many challenges in terms of practicality and actual security: to achieve high-speed key distribution, the system must use high-precision quantum state preparation modules (such as digital-to-analog converters, modulators) to modulate thousands of constellation points to approximate a continuous two-dimensional Gaussian distribution and rely on pilot light for phase reference. This not only greatly increases the complexity of the system but also poses extremely stringent requirements on the parameter matching of the devices.

[0005] In addition, continuous variable quantum key distribution also faces the risk of attacks by quantum hackers using the imperfections and vulnerabilities of actual devices. In particular, eavesdroppers may cause the phase reference at the receiving end to be inaccurate by changing the wavelength or intensity of the local oscillator light.

[0006] Although there have been proposed self-referenced continuous variable quantum key distribution schemes based on local local oscillators and pilot light for phase reference, new security vulnerabilities may be introduced because eavesdroppers can distinguish weak signal light from strong pilot light. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, the present invention proposes a continuous variable quantum key distribution method, device, and system. By adopting one-dimensional discrete modulation technology, the system architecture is significantly optimized on the premise of ensuring the security of key distribution.

[0008] The continuous variable quantum key distribution method is specifically as follows:

[0009] Step 1: The sender Alice uses a laser to generate continuous optical pulses, performs discretization encoding on a single quadrature component, and generates a one-dimensional discrete modulation signal;

[0010] Step 2: The discrete modulation signal passes through an attenuator to reduce the optical intensity to the quantum level, generating a quantum signal light, which is coupled to the quantum channel for transmission.

[0011] Step 3: The receiving end Bob uses a homodyne detector to self-calibrate and measure the canonical component of the quantum signal;

[0012] The calibration formula is:

[0013]

[0014] where x B and p B are the quadrature components at the Bob side, and θ is the phase drift angle;

[0015] Step 4: Adjust the local measurement basis direction in real time to dynamically compensate for the phase drift angle θ introduced by the quantum channel;

[0016] The dynamic compensation formula is:

[0017]

[0018] is the variance of the x component of mode A of the two-mode squeezed state shared by Alice and Bob; is the variance of the p component of mode A of the two-mode squeezed state shared by Alice and Bob; is the variance of the x component of mode B of the two-mode squeezed state shared by Alice and Bob; is the variance of the p component of mode B of the two-mode squeezed state shared by Alice and Bob; is the covariance of the x components of modes A and B of the two-mode squeezed state shared by Alice and Bob; is the covariance of the p components of modes A and B of the two-mode squeezed state shared by Alice and Bob;

[0019] Step 5: Using the calibrated canonical component and the dynamically compensated phase drift angle θ, calculate the covariance matrix of Alice and Bob;

[0020] The covariance matrix is expressed as:

[0021]

[0022] where V M is the modulation variance of Alice, ∈ x and ∈ p are the excess noises on the quadrature components x and p respectively, η x and η p are the channel transmittances on the quadrature components x and p respectively, C pis an unknown term in the covariance matrix, and σ is the variance of the phase drift angle. sinh and cosh are the hyperbolic sine function and the hyperbolic cosine function respectively.

[0023] Step 6: The post-processing module calculates the code rate of the system using the covariance matrix, determines whether the protocol between the receiver and the transmitter can generate a secure key. If so, perform subsequent error correction and privacy amplification, and finally generate a secure key. Otherwise, end the protocol communication between the receiver and the transmitter.

[0024] The continuous variable quantum key distribution device includes a transmitting device and a receiving device;

[0025] The transmitting device mainly consists of a laser, an intensity modulator, and an attenuator connected in sequence. The laser generates continuous optical pulses, which are input into the intensity modulator to achieve one-dimensional discrete modulation. After obtaining the modulation signal, it is input into the attenuator to generate quantum signal light, ensuring that the intensity of the quantum signal is at the quantum level;

[0026] The receiving device includes a polarization controller, a local oscillator laser, a homodyne detection module, an analog-to-digital converter, a digital signal processing module, and a post-processing module. The polarization controller receives the quantum signal light and controls the polarization direction of the quantum signal for dynamic calibration to ensure its match with the measurement basis direction at the receiving end. The analog-to-digital converter performs analog-to-digital conversion and data acquisition. The digital signal processing module performs dynamic phase calibration to compensate for the phase drift introduced by the channel. The local oscillator laser and the homodyne detection module jointly complete the real-time measurement of the quantum signal. Using the quantum signal with dynamically calibrated direction and the phase drift compensated dynamically, calculate the covariance matrix between the receiver and the transmitter, and input it into the post-processing module for further calculation of the code rate, and be responsible for tasks such as parameter estimation, reverse reconciliation, error correction, and privacy amplification.

[0027] The continuous variable quantum key distribution system consists of a transmitter and a receiver, forming a complete quantum key distribution link through a channel; the quantum signal generated by the transmitter is transmitted to the receiver through the channel, and the receiver completes the measurement and post-processing tasks of the quantum signal, and finally generates a secure key. The system adopts an asymmetric phase space coding mechanism, eliminating the dependence on the phase reference signal, and improving the security and stability of the system.

[0028] The protocol adopted between the transceiver ends of the system, through the statistical characteristics of one-dimensional discrete modulation and digital signal processing methods, uses the calibrated canonical component and the phase drift angle θ compensated dynamically to calculate the covariance matrix of the transceiver ends; replacing the traditional phase reference; the system hardware is simplified, removing the phase locking module of the traditional continuous variable quantum key distribution system, reducing the system complexity and cost.

[0029] The advantages of the present invention are:

[0030] 1. A continuous-variable quantum key distribution method that eliminates the phase reference attack surface: Through the design of a self-calibrating measurement basis for the phase space asymmetric state, it completely gets rid of the dependence on the pilot light in traditional continuous-variable quantum key distribution, effectively avoids the interference attack of eavesdroppers on the phase synchronization signal, and improves the security of the system.

[0031] 2. A continuous-variable quantum key distribution method that improves the dynamic anti-interference ability: The receiving end automatically calibrates the measurement direction through real-time data analysis, can compensate for the phase drift and noise interference introduced by the channel, thereby maintaining the stability of key generation, and enabling the system to operate efficiently and stably in a complex and changeable communication environment.

[0032] 3. A continuous-variable quantum key distribution method that simplifies the system architecture: Only the discretization encoding of a single quadrature component is required, reducing the demand for modulators, significantly simplifying the system architecture and hardware complexity; not only reducing the manufacturing cost of the system, but also improving the reliability and maintainability of the system.

[0033] 4. A continuous-variable quantum key distribution method that improves security: By adopting an asymmetric phase space encoding mechanism and self-calibrating measurement technology, it effectively eliminates the dependence on the phase reference and improves the system's ability to resist quantum hacker attacks. At the same time, the error correction and privacy amplification technologies in the post-processing module further enhance the security of the key.

[0034] 5. A continuous-variable quantum key distribution device not only improves security, but also reduces hardware complexity and cost, enhancing the practicality of the technology. This innovation makes the continuous-variable quantum key distribution technology more suitable for fields with high-security information transmission requirements such as national defense, government affairs, finance, and power.

[0035] 6. A continuous-variable quantum key distribution system has good scalability and compatibility, can be easily integrated and fused with other quantum communication technologies or classical communication technologies, providing a broad space for the wide application of quantum secure communication technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the step flow chart of a continuous-variable quantum key distribution method of the present invention;

[0037] Figure 2 is the schematic diagram of one-dimensional discrete modulation coherent state and calibration basis of the present invention;

[0038] Figure 3 is the structure diagram of the sending end in a continuous-variable quantum key distribution device of the present invention;

[0039] Figure 4 is the structure diagram of the receiving end in a continuous-variable quantum key distribution device of the present invention;

[0040] Figure 5 It is a schematic diagram of a continuous variable quantum key distribution system of the present invention. Specific embodiments

[0041] The following further elaborates in detail the specific implementation method of the present invention in conjunction with the accompanying drawings.

[0042] A continuous variable quantum key distribution method, device and system of the present invention, compared with the traditional continuous variable protocol that relies on two-dimensional Gaussian modulation or shared phase reference design schemes, is based on an asymmetric phase space coding mechanism and only needs to perform discrete modulation on a single quadrature component (such as four-state modulation), thus completely eliminating the dependence on the synchronous transmission of the phase reference signal. This design avoids the risk of eavesdroppers stealing keys through phase reference injection attacks (such as local oscillator pulse interception, phase compensation interference, etc.) from the physical layer source, and at the same time reduces the system complexity and the requirements for analog-to-digital converters and modulators, opening up a new path for the development of quantum secure communication technology.

[0043] The continuous variable quantum key distribution method, as Figure 1 shown, the specific steps are as follows:

[0044] Step 1: The sender Alice uses a laser to generate continuous optical pulses, performs discretization encoding on a single quadrature component to generate a one-dimensional discrete modulation signal;

[0045] The modulation values are selected from a predefined discrete set, avoiding the high computing power requirements for generating Gaussian distributed random numbers;

[0046] For example, one-dimensional four-state modulation can be predefined as encoding coherent states |-2α>, |-α>, |α>, |2α>, where α is the coherent state amplitude.

[0047] Step 2: The discrete modulation signal passes through an attenuator to reduce the optical intensity to the quantum level, generates a quantum signal light, and is coupled to the quantum channel for transmission.

[0048] Step 3: The receiver Bob uses a homodyne detector to self-calibrate and measure the canonical component of the quantum signal;

[0049] As Figure 2 shown, the phase rotation at the Bob side is defined by the input-output relationship:

[0050]

[0051] where, x B and p B are the quadrature components at the Bob side, and θ is the phase drift angle; generally satisfying a normal distribution with a mean of 0 and a variance of σ; after calibration, we get

[0052] Step 4: Adjust the local measurement basis direction in real time, and dynamically compensate for the phase drift angle θ introduced by the quantum channel without relying on pilot light synchronization;

[0053] For the variances in the x and p components of modes A and B of the two-mode squeezed state shared by Alice and Bob Covariance in the symmetric covariance matrix, the phase rotation of mode B causes the covariance matrix to become

[0054] The dynamic compensation formula is:

[0055]

[0056] is the variance of the x component of mode A of the two-mode squeezed state shared by Alice and Bob; is the variance of the p component of mode A of the two-mode squeezed state shared by Alice and Bob; is the variance of the x component of mode B of the two-mode squeezed state shared by Alice and Bob; is the variance of the p component of mode B of the two-mode squeezed state shared by Alice and Bob; is the covariance of the x components of modes A and B of the two-mode squeezed state shared by Alice and Bob; is the covariance of the p components of modes A and B of the two-mode squeezed state shared by Alice and Bob;

[0057] Step 5: Calculate the covariance matrices of Alice and Bob using the calibrated regular components and the dynamically compensated phase drift angle θ.

[0058] In general, due to the phase drift between the continuous signal and the pilot light, the angle θ of phase misalignment approximately follows a normal distribution with a mean of 0. After random phase rotation, the overall covariance matrix will be controlled by the expected values of each function. Therefore, in the case of phase misalignment, the covariance matrices of Alice and Bob are expressed as

[0059]

[0060] where V M is the modulation variance of Alice, ∈ x and ∈ p are the excess noises on the orthogonal components x and p respectively, η x and η p are the channel transmittances on the orthogonal components x and p respectively, C p is the unknown term in the covariance matrix, and σ is the variance of the phase drift angle. sinh and cosh are trigonometric functions.

[0061] Thus, this method can ensure security while being independent of any shared phase reference.

[0062] Step Six: The post-processing module calculates the code rate of the system using the covariance matrix, determines whether the protocol between the receiving end and the sending end can generate a secure key. If so, perform subsequent reverse reconciliation, error correction, and privacy amplification to finally generate a secure key. Otherwise, end the protocol communication between the receiving end and the sending end.

[0063] Bob sends part of the key information to Alice through the classical channel, and both parties perform parameter estimation, reverse reconciliation, error correction, and privacy amplification based on the shared key information to eliminate the impact of eavesdroppers on the key security.

[0064] The continuous variable quantum key distribution device includes a sending device and a receiving device;

[0065] As Figure 3 shown, the sending device mainly consists of a laser (1550nm band), an intensity modulator, and an attenuator connected in sequence. The laser generates continuous optical pulses, which are input into the intensity modulator to achieve one-dimensional discrete modulation. After obtaining the modulation signal, it is input into the attenuator to generate quantum signal light, ensuring that the intensity of the quantum signal is at the quantum level;

[0066] As Figure 4 shown, the receiving device includes a polarization controller, a local oscillator laser, a homodyne detection module, an analog-to-digital converter, a digital signal processing module, and a post-processing module. The polarization controller receives the quantum signal light and controls the polarization direction of the quantum signal for dynamic calibration to ensure its matching with the measurement basis direction at the receiving end. The analog-to-digital converter performs analog-to-digital conversion and data acquisition. The digital signal processing module performs dynamic phase calibration to compensate for the phase drift introduced by the channel. The local oscillator laser and the homodyne detection module jointly complete the real-time measurement of the quantum signal. Using the quantum signal with dynamically calibrated direction and the dynamically compensated phase drift, the covariance matrix between the receiving end and the sending end is calculated and input into the post-processing module for further code rate calculation, and is responsible for tasks such as parameter estimation, raw key generation, error correction, and privacy amplification.

[0067] The innovation of the device lies in: adopting a new type of discrete modulation device to achieve one-dimensional discrete modulation, directly avoiding the dependence on the phase reference signal.

[0068] As Figure 5As shown, the continuous variable quantum key distribution system consists of a sending end and a receiving end, forming a complete quantum key distribution link through a channel. The quantum signal generated by the sending end is transmitted to the receiving end through the channel. The receiving end completes the measurement and post-processing tasks of the quantum signal, and finally generates a secure key. The system adopts an asymmetric phase space encoding mechanism, eliminating the dependence on the phase reference signal and improving the security and stability of the system.

[0069] The protocol adopted between the transceiver ends of the system uses the statistical characteristics of one-dimensional discrete modulation and digital signal processing methods, and calculates the covariance matrix of the transceiver ends by using the calibrated regular component and the phase drift angle θ after dynamic compensation, replacing the traditional phase reference. The system hardware is simplified, the phase locking module of the traditional continuous variable quantum key distribution system is removed, reducing the system complexity and cost.

[0070] In summary, the continuous variable quantum key distribution method, device and system proposed by the present invention significantly simplify the system architecture, reduce the hardware complexity, improve the practicability and stability of the system while maintaining high security. This innovation not only opens up a new path for the development and application of quantum secure communication technology, but also provides strong technical support for the construction of future quantum communication networks.

Claims

1. A continuous variable quantum key distribution method, characterized in that: The specific steps are as follows: Step 1: Alice at the transmitting end generates continuous optical pulses using a laser, performs discretization encoding on a single orthogonal component, and generates a one-dimensional discrete modulation signal; Step 2: The discrete modulated signal is attenuated to reduce the light intensity to the quantum level, generating quantum signal light, and coupled to the quantum channel for transmission; Step 3: The receiving end Bob uses a homodyne detector to self-calibrate and measure the canonical component of the quantum signal; Step 4: Adjust the local measurement base direction in real time to dynamically compensate for the phase drift angle θ introduced by the quantum channel; The dynamic compensation formula is: is the x-component variance of mode A in the two-mode squeezed state shared by Alice and Bob; is the p-component variance of mode A in the two-mode squeezed state shared by Alice and Bob; is the x-component variance of mode B in the two-mode squeezed state shared by Alice and Bob; is the p-component variance of mode B in the two-mode squeezed state shared by Alice and Bob; is the x-component covariance of modes A and B in the two-mode squeezed state shared by Alice and Bob; is the p-component covariance of modes A and B in the two-mode squeezed state shared by Alice and Bob; Step 5: Calculate the covariance matrix of Alice and Bob using the calibrated regular component and the phase drift angle θ after dynamic compensation; The covariance matrix is ​​expressed as: Among them, V M is Alice’s modulation variance, ∈ x and ∈ p are the excess noise on the orthogonal components x and p, respectively, η x and η p are the channel transmittances on the orthogonal components x and p, respectively, and C p is the unknown term in the covariance matrix, σ is the variance of the phase drift angle; Step 6: The post-processing module uses the covariance matrix to calculate the system code rate and determine whether the protocol between the receiving end and the sending end can generate a security key. If so, subsequent reverse coordination, error correction and confidentiality enhancement are performed to finally generate a security key; otherwise, the protocol communication between the receiving end and the sending end is terminated.

2. A continuous variable quantum key distribution method as claimed in claim 1, characterized in that: The calibration formula of step three is: Among them, x B and p B is the orthogonal component at the Bob end, and θ is the phase shift angle.

3. A continuous variable quantum key distribution device based on a continuous variable quantum key distribution method according to claim 1, characterized in that: comprising a sending device and a receiving device; The transmitting device mainly consists of a laser, an intensity modulator and an attenuator connected in sequence; The laser generates continuous light pulses, which are input into the intensity modulator to achieve one-dimensional discrete modulation. After the modulated signal is obtained, it is input into the attenuator to generate quantum signal light to ensure that the quantum signal intensity is at the quantum level. The receiving device includes a polarization controller, a local oscillator laser, a homodyne detection module, a digital-to-analog converter, a digital signal processing module and a post-processing module; The polarization controller receives quantum signal light and controls the polarization direction of the quantum signal for dynamic calibration to ensure that it matches the measurement base direction of the receiving end. The digital-to-analog converter performs digital-to-analog conversion and data acquisition. The digital signal processing module performs dynamic phase calibration to compensate for the phase drift introduced by the channel. The local oscillator laser and the homodyne detector jointly complete the real-time measurement of the quantum signal. The covariance matrix between the receiving end and the transmitting end is calculated using the quantum signal in the dynamic calibration direction and the dynamically compensated phase drift. The input post-processing module further calculates the code rate and is responsible for tasks such as parameter estimation, original key generation, error correction, and confidentiality enhancement.

4. A continuous variable quantum key distribution system based on a continuous variable quantum key distribution method according to claim 1, characterized in that: A complete quantum key distribution link consisting of a transmitter and a receiver through a channel; The quantum signal generated by the transmitting end is transmitted to the receiving end through the channel. The receiving end completes the measurement and post-processing tasks of the quantum signal and finally generates a security key.

5. The continuous variable quantum key distribution system according to claim 4, characterized in that: The asymmetric phase space encoding mechanism is adopted to eliminate the dependence on the phase reference signal and improve the security and stability of the system.

6. The continuous variable quantum key distribution system according to claim 4 or 5, characterized in that: The protocol adopted between the transmitting and receiving ends of the system calculates the covariance matrix of the transmitting and receiving ends by using the statistical characteristics of one-dimensional discrete modulation and a digital signal processing method, using the calibrated regular component and the phase drift angle θ after dynamic compensation, replacing the traditional phase reference; and removing the traditional phase locking module.

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