Multi-channel continuous variable quantum key distribution method and system based on frequency division multiplexing

Abstract

The invention discloses a multi-channel continuous variable quantum key distribution method and system based on frequency division multiplexing. The system comprises a sending end signal generation and modulation module and a receiving end signal detection module. The transmitting end signal generation and modulation module is composed of an arbitrary waveform generator, a laser transmitter, an IQ modulator, a variable optical attenuator, an optical beam splitter and an optical isolator. The receiving end signal detection module is composed of two homodyne detectors, a variable optical attenuator, an optical isolator and an optical beam splitter. According to the invention, a composite optical signal formed by mixing a plurality of Gaussian modulation coherent state quantum signals is generated through the sending end signal generation and modulation module, the composite optical signal is detected by the receiving end signal detection module after being transmitted, and then coherent demodulation, filtering, phase drift recovery and parameter evaluation are carried out on the received composite optical signal. And finally, separation of the multiple quantum signals is completed in the frequency domain, and frequency division multiplexing of the multiple paths of quantum signals on the same channel is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum secure communication, and in particular relates to a multi-channel continuous variable quantum key distribution method and system based on frequency division multiplexing. Background Art

[0002] Quantum Key Distribution (QKD) is a cutting-edge technology based on the principles of quantum mechanics that can generate and distribute symmetric keys between communicating parties that cannot be eavesdropped or cracked. Unlike traditional encryption schemes, quantum key distribution relies on the basic principles of quantum physics, such as the uncertainty principle and the quantum no-cloning theorem, which fundamentally guarantees the security of communications. The practical application of quantum key distribution has entered the preliminary verification stage worldwide and has shown great potential in the field of information security. In recent years, some countries and companies have invested resources to actively promote the research and development and deployment of quantum encryption networks, and have carried out experimental and commercial application demonstrations of quantum key distribution technology in different regions and fields, showing its broad application prospects in finance, government, military and highly sensitive information transmission.

[0003] Quantum key distribution is mainly divided into two categories: discrete variable quantum key distribution (DV-QKD) and continuous variable quantum key distribution (CV-QKD). Different from discrete variable quantum key distribution, continuous variable quantum key distribution achieves key distribution by continuously modulating quantum states, and performs better in terms of compatibility with existing optical fiber communication systems. Although continuous variable quantum key distribution has high potential in theory, its practical application still faces many challenges, especially the limitation of channel capacity and the complexity of the system. Frequency division multiplexing (FDM), as one of the core technologies of modern communications, can make full use of bandwidth resources by multiplexing multiple signal carriers at different frequencies. Applying frequency division multiplexing to the continuous variable quantum key distribution system and transmitting multiple quantum signals simultaneously on multiple frequency channels can greatly improve the key generation rate and transmission efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-channel continuous variable quantum key distribution method and system based on frequency division multiplexing, which uses a single channel to realize the co-transmission of multi-channel quantum signals; and, in actual implementation, the method only requires one set of communication transceiver equipment, which significantly reduces the deployment difficulty and overhead of continuous variable quantum key distribution technology.

[0005] To solve the above problems, the technical solution of the present invention is: A multi-channel continuous variable quantum key distribution system based on frequency division multiplexing, comprising: a signal generation and modulation module at a transmitting end and a signal detection module at a receiving end; The transmitting end signal generation and modulation module is composed of an arbitrary waveform generator, a laser transmitter, an IQ modulator, a first variable optical attenuator, a first optical beam splitter and a first optical isolator; the receiving end signal detection module is composed of two homodyne detectors, a second variable optical attenuator, a second optical isolator and a second optical beam splitter; The first channel and the second channel of the arbitrary waveform generator are connected to the corresponding interface of the IQ modulator; the laser transmitter is connected to the first optical beam splitter, one output of the first optical beam splitter is connected to the first optical isolator and connected to the corresponding interface of the IQ modulator; the output end of the IQ modulator is connected to the first variable optical attenuator and then connected to the receiving end signal detection module; the other output of the first optical beam splitter is directly connected to the receiving end signal detection module; In the receiving end signal detection module, the input end of one channel of the second optical beam splitter is connected to the first variable optical attenuator, and the output end of the second optical beam splitter is connected to two homodyne detectors; the input end of another channel of the second optical beam splitter is connected to the second variable optical attenuator, the second optical isolator and the first optical beam splitter in sequence, and the output end of the second optical beam splitter is connected to two homodyne detectors.

[0006] According to an embodiment of the present invention, the first optical beam splitter is a 1:99 optical beam splitter, and the second optical beam splitter is a 50:50 optical beam splitter.

[0007] A multi-channel continuous variable quantum key distribution method based on frequency division multiplexing, using a multi-channel continuous variable quantum key distribution system based on frequency division multiplexing, comprising the following steps: Build a system to realize frequency division multiplexing of multi-channel Gaussian modulated coherent state protocol quantum signals, including a transmitter signal generation and modulation module and a receiver signal detection module; Generate multiple Gaussian distribution sequences and add sinusoidal carriers to form continuous waveforms; then add the multiple waveforms and connect them to the arbitrary waveform generator in the signal generation and modulation module at the transmitting end to obtain a composite electrical signal formed by mixing multiple Gaussian modulated coherent state quantum signals; The composite electrical signal output by the electrical signal generation module in the signal generation and modulation module at the transmitting end is used as the driving signal, and the optical signal output by the laser transmitter is used as the carrier. The composite optical signal carrying information after modulation is returned to the second optical beam splitter at the same time to interfere. The interference result enters the signal detection module at the receiving end, and coherent detection is realized through two balanced homodyne detectors. The detected signal is coherently demodulated by the signal detection module at the receiving end to achieve multi-path quantum signal separation, filtering, phase drift recovery and parameter evaluation.

[0008] According to an embodiment of the present invention, for the k-th Gaussian modulated coherent state quantum signal, the sine wave carrier formula is: ; ; in, and is a random sequence that follows a Gaussian distribution, is the carrier frequency, t is the time; let ,make , and That is, it is a composite electrical signal of the n-channel Gaussian modulated coherent state quantum signal generated by the access transmitting end signal and the modulation module.

[0009] According to an embodiment of the present invention, the carrier frequencies of a plurality of Gaussian modulated coherent state quantum signals are different from each other so as to separate the multi-path signals in the spectrum.

[0010] According to an embodiment of the present invention, the receiving end signal detection module performs coherent demodulation on the detected signal, including: X and P are two regular components of the light field. In the initial state, X and P are equal to and , X and P have a phase drift during transmission , it is deduced that: , ; Will and Substituting X and P, we get: , ; The coherent demodulation of the j-th Gaussian modulated coherent state quantum signal includes: Multiply X and P by , sorted out: , ; in, is the carrier frequency of the kth signal, is the carrier frequency of the jth signal, and are far greater than 0, and low-pass filtering is performed to further separate , , So as to further restore the original Gaussian distribution sequence and .

[0011] According to an embodiment of the present invention, the receiving end signal detection module performs phase drift recovery on the detected signal, including: Gaussian modulated coherent state quantum signal Multiply by , change the variable , and calculate ( ) The real and imaginary parts of and The cross-correlation function value is the maximum when the cross-correlation function value is The value is the drift phase ; Known After the value, through the simultaneous equations , the solution is and .

[0012] According to an embodiment of the present invention, the receiving end signal detection module performs parameter evaluation on the detected signal including: The electrical noise, shot noise, over-noise and signal-to-noise ratio parameters of each Gaussian modulated coherent state quantum signal are calculated to evaluate whether quantum communication is unconditionally secure and whether the communication quality meets the standards.

[0013] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: In one embodiment of the present invention, a multi-channel continuous variable quantum key distribution method based on frequency division multiplexing aims at the problem of channel capacity limitation and complex system in continuous variable quantum key distribution. A transmitting end signal generation and modulation module composed of an arbitrary waveform generator, a laser transmitter, an IQ modulator, a variable optical attenuator, an optical beam splitter and an optical isolator, and a receiving end signal detection module composed of two homodyne detectors, a variable optical attenuator, an optical isolator and an optical beam splitter are used to generate multiple Gaussian distribution sequences and add sinusoidal carriers respectively to form continuous waveforms. Then, the multiple waveforms are added and sent to the arbitrary waveform generator in the transmitting end signal generation and modulation module. This is a multi-channel Gaussian modulated coherent state quantum signal mixing method. The composite electrical signal is composed of the composite electrical signal output by the electrical signal generation module in the signal generation and modulation module at the transmitting end as the driving signal, and the optical signal output by the laser transmitter as the carrier, which is modulated by the IQ modulator. The modulated composite optical signal carrying information returns to the 50:50 beam splitter at the same time to interfere. The interference result enters the signal detection module at the receiving end, and coherent detection is achieved through two balanced homodyne detectors; the detected signal is coherently demodulated by the signal detection module at the receiving end to achieve multi-channel quantum signal separation, filtering, phase drift recovery, and parameter evaluation, and finally the separation of multiple quantum signals is completed in the frequency domain, realizing the frequency division multiplexing of multiple quantum signals on the same channel. Moreover, in actual implementation, only one set of communication transceiver equipment is required, which significantly reduces the deployment difficulty and overhead of continuous variable quantum key distribution technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of a multi-channel continuous variable quantum key distribution system based on frequency division multiplexing in one embodiment of the present invention; Figure 2 The flowchart of the multi-channel continuous variable quantum key distribution method based on frequency division multiplexing in one embodiment of the present invention. DETAILED DESCRIPTION

[0015] The following is a further detailed description of a multi-channel continuous variable quantum key distribution method and system based on frequency division multiplexing proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims.

[0016] Please see Figure 1This embodiment provides a multi-channel continuous variable quantum key distribution system based on frequency division multiplexing, which includes a transmitting end and a receiving end. The transmitting end includes a transmitting end signal generation and modulation module composed of an arbitrary waveform generator 1, a laser transmitter 2, an IQ modulator 3, a first variable optical attenuator 4, a first optical beam splitter 5 and a first optical isolator 6, and the receiving end includes a receiving end signal detection module composed of two homodyne detectors 7, a second variable optical attenuator 8, a second optical isolator 9 and a second optical beam splitter 10. The first channel and the second channel of the arbitrary waveform generator 1 are connected to the corresponding interface of the IQ modulator 3; the laser transmitter 2 is connected to the first optical beam splitter 5, and one output of the first optical beam splitter 5 is connected to the first optical isolator 6 and connected to the corresponding interface of the IQ modulator 3; the output end of the IQ modulator 3 is connected to the first variable optical attenuator 4 and then connected to the receiving end signal detection module. The other output of the first optical beam splitter 5 is directly connected to the receiving end signal detection module.

[0017] In the signal detection module at the receiving end, the input end of one second optical beam splitter 10 is connected to the first variable optical attenuator 4, and the output end of the second optical beam splitter 10 is connected to two homodyne detectors 7; the input end of another second optical beam splitter 10 is connected to the second variable optical attenuator 8, the second optical isolator 9 and the first optical beam splitter 5 in sequence, and the output end of the second optical beam splitter 10 is connected to two homodyne detectors 7.

[0018] In practical applications, the first optical beam splitter is a 1:99 optical beam splitter, and the second optical beam splitter is a 50:50 optical beam splitter.

[0019] When the above-mentioned multi-channel continuous variable quantum key distribution system based on frequency division multiplexing performs quantum key distribution, the following method is adopted, namely, the multi-channel continuous variable quantum key distribution method based on frequency division multiplexing, please refer to Figure 2 , the method comprises the following steps: (1) Build a system to realize frequency division multiplexing of multi-channel Gaussian modulated coherent state protocol quantum signals, including a transmitter signal generation and modulation module and a receiver signal detection module; (2) Generate multiple Gaussian distribution sequences and add sinusoidal carriers to each of them to form a continuous waveform; then add the multiple waveforms together and connect them to the arbitrary waveform generator in the signal generation and modulation module at the transmitting end to obtain a composite electrical signal composed of multiple Gaussian modulated coherent state quantum signals; (3) The composite electrical signal output by the electrical signal generation module in the signal generation and modulation module at the transmitting end is used as the driving signal, and the optical signal output by the laser transmitter is used as the carrier. The composite optical signal carrying information after modulation is returned to the second optical beam splitter at the same time to interfere. The interference result enters the signal detection module at the receiving end, and coherent detection is realized through two balanced homodyne detectors. (4) The detected signal is coherently demodulated by the signal detection module at the receiving end to achieve multi-path quantum signal separation, filtering, phase drift recovery and parameter evaluation.

[0020] Among them, for the k-th Gaussian modulated coherent state quantum signal, the sine wave carrier formula is: ; ; in, and is a random sequence that follows a Gaussian distribution, is the carrier frequency, t is the time; let ,make , and That is, it is a composite electrical signal of the n-channel Gaussian modulated coherent state quantum signal generated by the access transmitting end signal and the modulation module.

[0021] The carrier frequencies of multiple Gaussian modulated coherent state quantum signals are different from each other so as to separate the multiple signals in the spectrum.

[0022] The receiving end signal detection module performs coherent demodulation on the detected signal including: X and P are two regular components of the light field. In the initial state, X and P are equal to and , X and P have a phase drift during transmission , it is deduced that: , ; Will and Substituting X and P, we get: , ; The coherent demodulation of the j-th Gaussian modulated coherent state quantum signal includes: Multiply X and P by , sorted out: , ; in, is the carrier frequency of the kth signal, is the carrier frequency of the jth signal, and are far greater than 0, and low-pass filtering is performed to further separate , , So as to further restore the original Gaussian distribution sequence and .

[0023] The signal detection module at the receiving end performs phase drift recovery on the detected signal including: Gaussian modulated coherent state quantum signal Multiply by , change the variable , and calculate ( ) The real and imaginary parts of and The cross-correlation function value is the maximum when the cross-correlation function value is The value is the drift phase ; Known After the value, through the simultaneous equations , the solution is and .

[0024] The receiving end signal detection module performs parameter evaluation on the detected signal including: The electric noise, shot noise, over-noise and signal-to-noise ratio parameters of each Gaussian modulated coherent state quantum signal are calculated to evaluate whether quantum communication has unconditional security and whether the communication quality meets the standard. The calculation method of the electric noise, shot noise, over-noise and signal-to-noise ratio here can be implemented using existing technologies and will not be introduced in detail here.

[0025] In summary, the present invention generates a composite optical signal formed by mixing multiple Gaussian modulated coherent state quantum signals through a signal generation and modulation module at the transmitting end, which is detected by a signal detection module at the receiving end after transmission, and then the received composite optical signal is coherently demodulated, filtered, phase drift recovered and parameter evaluated, and finally the multiple quantum signals are separated in the frequency domain, thereby realizing frequency division multiplexing of multiple quantum signals on the same channel.

[0026] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A multi-channel continuous variable quantum key distribution system based on frequency division multiplexing, characterized in that: include: A signal generation and modulation module at the transmitting end and a signal detection module at the receiving end; The transmitting end signal generation and modulation module is composed of an arbitrary waveform generator, a laser transmitter, an IQ modulator, a first variable optical attenuator, a first optical beam splitter and a first optical isolator; the receiving end signal detection module is composed of two homodyne detectors, a second variable optical attenuator, a second optical isolator and a second optical beam splitter; The first channel and the second channel of the arbitrary waveform generator are connected to the corresponding interface of the IQ modulator; the laser transmitter is connected to the first optical beam splitter, one output of the first optical beam splitter is connected to the first optical isolator and connected to the corresponding interface of the IQ modulator; the output end of the IQ modulator is connected to the first variable optical attenuator and then connected to the receiving end signal detection module; the other output of the first optical beam splitter is directly connected to the receiving end signal detection module; In the receiving end signal detection module, the input end of one channel of the second optical beam splitter is connected to the first variable optical attenuator, and the output end of the second optical beam splitter is connected to two homodyne detectors; the input end of another channel of the second optical beam splitter is connected to the second variable optical attenuator, the second optical isolator and the first optical beam splitter in sequence, and the output end of the second optical beam splitter is connected to two homodyne detectors.

2. The frequency division multiplexing-based multi-channel continuous variable quantum key distribution system according to claim 1, characterized in that: The first optical beam splitter is a 1:99 optical beam splitter, and the second optical beam splitter is a 50:50 optical beam splitter.

3. A multi-channel continuous variable quantum key distribution method based on frequency division multiplexing, using the multi-channel continuous variable quantum key distribution system based on frequency division multiplexing according to claim 1, characterized in that: The following steps are involved: Build a system to realize frequency division multiplexing of multi-channel Gaussian modulated coherent state protocol quantum signals, including a transmitter signal generation and modulation module and a receiver signal detection module; Generate multiple Gaussian distribution sequences and add sinusoidal carriers to form continuous waveforms; then add the multiple waveforms and connect them to the arbitrary waveform generator in the signal generation and modulation module at the transmitting end to obtain a composite electrical signal formed by mixing multiple Gaussian modulated coherent state quantum signals; The composite electrical signal output by the electrical signal generation module in the signal generation and modulation module at the transmitting end is used as the driving signal, and the optical signal output by the laser transmitter is used as the carrier. The composite optical signal carrying information after modulation is returned to the second optical beam splitter at the same time to interfere. The interference result enters the signal detection module at the receiving end, and coherent detection is realized through two balanced homodyne detectors. The detected signal is coherently demodulated by the signal detection module at the receiving end to achieve multi-path quantum signal separation, filtering, phase drift recovery and parameter evaluation.

4. The multi-channel continuous variable quantum key distribution method based on frequency division multiplexing according to claim 3 is characterized in that: For the k-th Gaussian modulated coherent state quantum signal, the sine wave carrier formula is: ； ； in, and is a random sequence that follows a Gaussian distribution, is the carrier frequency, t is the time; let ,make , and That is, it is a composite electrical signal of the n-channel Gaussian modulated coherent state quantum signal generated by the access transmitting end signal and the modulation module.

5. The multi-channel continuous variable quantum key distribution method based on frequency division multiplexing according to claim 4 is characterized in that: The carrier frequencies of multiple Gaussian modulated coherent state quantum signals are different from each other so as to separate the multiple signals in the spectrum.

6. The multi-channel continuous variable quantum key distribution method based on frequency division multiplexing according to claim 5, characterized in that: The receiving end signal detection module performs coherent demodulation on the detected signal including: X and P are two regular components of the light field. In the initial state, X and P are equal to and , X and P have a phase drift during transmission , it is deduced that: ， ； Will and Substituting X and P, we get: ， ； The coherent demodulation of the j-th Gaussian modulated coherent state quantum signal includes: Multiply X and P by , sorted out: ， ； in, is the carrier frequency of the kth signal, is the carrier frequency of the j-th signal, and are far greater than 0, and low-pass filtering is performed to further separate ， ， So as to further restore the original Gaussian distribution sequence and .

7. The multi-channel continuous variable quantum key distribution method based on frequency division multiplexing according to claim 6, characterized in that: The signal detection module at the receiving end performs phase drift recovery on the detected signal including: Gaussian modulated coherent state quantum signal Multiply by , change the variable , and calculate ( ) The real and imaginary parts of and The cross-correlation function value is the maximum when the cross-correlation function value is The value is the drift phase ; Known After the value, through the simultaneous equations , the solution is and .

8. The multi-channel continuous variable quantum key distribution method based on frequency division multiplexing according to claim 3, characterized in that: The receiving end signal detection module performs parameter evaluation on the detected signal including: The electrical noise, shot noise, over-noise and signal-to-noise ratio parameters of each Gaussian modulated coherent state quantum signal are calculated to evaluate whether quantum communication is unconditionally secure and whether the communication quality meets the standards.

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