A multi-carrier continuous-variable quantum key distribution system and method

Abstract

The application relates to the technical field of quantum secure communication, and discloses a multi-carrier continuous variable quantum key distribution system and method, which comprises a multi-carrier quantum key generation module, a multi-carrier quantum state preparation module, an optical fiber channel, a multi-carrier quantum state detection module and a multi-carrier quantum key processing module. The application effectively avoids the influence of the dispersion effect of the optical fiber channel on the wideband CV-QKD system, improves the data processing performance of the wideband and long-distance CV-QKD system under an ultra-low signal-to-noise ratio, realizes an N-way CV-QKD system with different modulation protocols, and guarantees high-flexibility, high-practicability and high-code-rate quantum secure communication.

Description

Technical Field

[0001] This invention relates to the field of quantum secure communication technology, specifically a multi-carrier continuous variable quantum key distribution system and method. Background Technology

[0002] In recent years, continuous variable quantum key distribution (CV-QKD) has made significant progress in quantum state preparation, transmission, detection, and data processing. As a result, researchers both domestically and internationally have begun developing mature and stable CV-QKD systems and deploying them in existing fiber optic communication systems. However, for CV-QKD systems to become practical, further research is needed on high-speed, long-distance, and multi-protocol compatible high-performance CV-QKD systems.

[0003] Currently, the main technical approaches to improving the secure bit rate and transmission distance of CV-QKD systems are to increase the system repetition frequency and reduce system noise. However, with the surge in demands for transmission distance and secure bit rate in CV-QKD systems, increasing the system repetition frequency and optimizing noise are gradually facing technical bottlenecks. On the one hand, as the repetition frequency of CV-QKD systems increases, broadband CV-QKD systems are highly susceptible to effects such as fiber dispersion during long-distance transmission, resulting in significant additional noise and limiting the transmission distance of broadband CV-QKD systems. This makes it difficult to achieve high-performance CV-QKD systems; for example, the dispersion-limited distance of a 10GHz broadband fiber optic transmission system is 50km. On the other hand, high-speed, long-distance CV-QKD systems are affected by low broadband detection efficiency and long-term fiber disturbances, leading to a low signal-to-noise ratio and insufficient data processing performance, such as insufficient digital signal processing accuracy and post-processing error correction efficiency. To address the aforementioned issues, the high-speed CV-QKD system needs to be converted into a multi-channel low-speed CV-QKD system to reduce the impact of chromatic dispersion in the fiber optic channel, thereby improving the transmission distance and secure code rate of the CV-QKD system. Simultaneously, high-performance digital signal demodulation and post-processing algorithms are required to ensure accurate demodulation and efficient error correction of the quantum key signal under low signal-to-noise ratio conditions, reducing system noise and guaranteeing a high secure code rate output. Furthermore, to enhance the practicality of the CV-QKD system, improve its compatibility with classical optical communication, and establish a flexible quantum communication network, the CV-QKD system needs to implement a flexible and adjustable modulation protocol to adapt to the quantum secure communication needs of different channels and users. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a multi-carrier continuous variable quantum key distribution system and method, which solves the problems of high-speed CV-QKD systems being affected by fiber dispersion effects and having limited data processing performance under ultra-low signal-to-noise ratio during long-distance transmission.

[0005] The technical solution adopted by the present invention to solve the above problems is:

[0006] A multi-carrier continuous-variable quantum key distribution system includes a multi-carrier quantum key generation module, a multi-carrier quantum state preparation module, an optical fiber channel, a multi-carrier quantum state detection module, and a multi-carrier quantum key processing module; wherein, the multi-carrier quantum key generation module is electrically connected to the multi-carrier quantum state preparation module, the multi-carrier quantum state preparation module, the optical fiber channel, and the multi-carrier quantum state detection module are sequentially optically connected, and the multi-carrier quantum state detection module is electrically connected to the multi-carrier quantum key processing module.

[0007] As a preferred technical solution, the multi-carrier quantum key generation module is used to: convert high-speed quantum keys into N orthogonal low-speed quantum key electrical signals and input them into the multi-carrier quantum state preparation module; where N≥2 and N is an integer;

[0008] The multi-carrier quantum state preparation module is used to: generate multi-carrier quantum optical signals and pilot optical signals, and then send the generated multi-carrier quantum optical signals and pilot optical signals into the optical fiber channel for transmission;

[0009] The multi-carrier quantum state detection module is used to: receive multi-carrier quantum optical signals and pilot optical signals transmitted through optical fiber channels, and then perform coherent detection on the multi-carrier quantum optical signals and pilot optical signals to form multi-carrier quantum electrical signals and pilot electrical signals;

[0010] The multi-carrier quantum key processing module is used to generate N quantum keys based on multi-carrier quantum electrical signals and pilot electrical signals.

[0011] As a preferred technical solution, the multi-carrier quantum key generation module includes a random number generator, a serial-to-parallel conversion submodule, a modulation submodule, a first insertion submodule, an inverse Fourier transform submodule, a parallel-to-serial conversion submodule, a second insertion submodule, a first matched filter submodule, a frequency shifting submodule, a real / imaginary part extraction submodule, and a digital-to-analog converter, which are connected in sequence.

[0012] As a preferred technical solution, the multi-carrier quantum state preparation module includes an Alice laser, a third polarization beam splitter, an IQ modulator, a first optical attenuator, and a polarization beam combiner connected by optical fibers. The multi-carrier quantum state preparation module also includes a second optical attenuator that is optically connected to the third polarization beam splitter and the polarization beam combiner respectively. The input end of the IQ modulator is electrically connected to the output end of the digital-to-analog converter, and the polarization beam combiner is optically connected to the optical fiber channel.

[0013] As a preferred technical solution, the multi-carrier quantum state detection module includes a Bob laser, a first polarization beam splitter, a first optical coupler, a second optical coupler, and a second polarization beam splitter connected in sequence by optical fibers. The first polarization beam splitter is optically connected to the first optical coupler, the first optical coupler is optically connected to the second polarization beam splitter, and the second polarization beam splitter is optically connected to the optical fiber channel. It also includes a first balanced detector and a second balanced detector. The first optical coupler is optically connected to the first balanced detector, and the second optical coupler and the second balanced detector are optically connected.

[0014] As a preferred technical solution, the multi-carrier quantum key processing module includes an analog-to-digital converter, a frequency offset estimation submodule, a bandpass filter submodule, a pilot compensation submodule, a matched filter submodule, a clock synchronization submodule, a cyclic prefix removal submodule, a second serial-to-parallel conversion submodule, a Fourier transform submodule, an extraction / removal submodule, a digital equalization compensation submodule, and a data post-processing submodule connected in sequence. The analog-to-digital converter is electrically connected to the first balanced detector and the second balanced detector, respectively.

[0015] As a preferred technical solution, the first insertion submodule is used to insert the training sequence and the zero sequence, and the second insertion submodule is used to insert the cyclic prefix.

[0016] As a preferred technical solution, the extraction / removal submodule is used to extract the training sequence and remove zero sequences, and the digital equalization compensation submodule is used to implement digital equalization compensation based on the training sequence.

[0017] As a preferred technical solution, N=5.

[0018] A multi-carrier continuous-variable quantum key distribution method, employing the aforementioned multi-carrier continuous-variable quantum key distribution system, operates as follows:

[0019] The multi-carrier quantum key generation module converts high-speed quantum keys into N orthogonal low-speed quantum key electrical signals and inputs them into the multi-carrier quantum state preparation module;

[0020] The multi-carrier quantum state preparation module generates multi-carrier quantum optical signals and pilot optical signals, which are then sent into the optical fiber channel for transmission.

[0021] The multi-carrier quantum state detection module receives multi-carrier quantum optical signals and pilot optical signals transmitted through an optical fiber channel, and then performs coherent detection on the multi-carrier quantum optical signals and pilot optical signals to form multi-carrier quantum electrical signals and pilot electrical signals;

[0022] The multi-carrier quantum key processing module generates N quantum keys based on multi-carrier quantum electrical signals and pilot electrical signals.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) By introducing multi-carrier technology, this invention converts the high-speed CV-QKD system into an N-channel low-speed CV-QKD system, effectively weakening the inter-symbol interference caused by the long-distance fiber dispersion effect of the high-speed CV-QKD system, and effectively improving the transmission distance and security code rate of the CV-QKD system.

[0025] (2) This invention proposes a digital processing algorithm for N-way quantum orthogonal subcarriers, which effectively improves the accuracy of digital signal processing in high-speed, long-distance CV-QKD systems with low signal-to-noise ratio, and ensures the effective realization of high-performance CV-QKD systems;

[0026] (3) By adopting N-way quantum orthogonal subcarrier parallel transmission technology, this invention can realize the parallel distribution of continuous variable quantum keys with different modulation protocols, effectively meet the encryption requirements of different transmission channels and different users, and improve the compatibility of CV-QKD system with classical optical communication system. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a multi-carrier continuous variable quantum key distribution system according to the present invention.

[0028] The labels and their corresponding names in the attached diagram are as follows: 1. Multi-carrier quantum key generation module; 2. Multi-carrier quantum state preparation module; 3. Optical fiber channel; 4. Multi-carrier quantum state detection module; 5. Multi-carrier quantum key processing module; 11. Random number generator; 12. Serial-to-parallel conversion submodule; 13. Modulation submodule; 14. First insertion submodule; 15. Inverse Fourier transform submodule; 16. Parallel-to-serial conversion submodule; 17. Second insertion submodule; 18. First matched filter submodule; 19. Frequency shifting submodule; 110. Real / imaginary part extraction submodule; 111. Digital-to-analog converter; 21. Alice laser; 22. Third polarization beam splitter; 23. IQ modulator; 24. First optical attenuator. 25. Second optical attenuator, 26. Polarization beam combiner, 41. Bob laser, 42. First polarization beam splitter, 43. First optical coupler, 44. Second optical coupler, 45. Second polarization beam splitter, 46. First balanced detector, 47. Second balanced detector, 51. Analog-to-digital converter, 52. Frequency offset estimation submodule, 53. Bandpass filter submodule, 54. Pilot compensation submodule, 55. Matched filter submodule, 56. Clock synchronization submodule, 57. Cyclic prefix removal submodule, 58. Second serial-to-parallel conversion submodule, 59. Fourier transform submodule, 510. Extraction / removal submodule, 511. Digital equalization compensation submodule, 512. Data post-processing submodule. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0030] Example 1

[0031] like Figure 1 As shown, this invention addresses the limitations of high-speed CV-QKD systems in long-distance transmission due to fiber dispersion and data processing performance under ultra-low signal-to-noise ratio. It also enables parallel distribution of continuous-variable quantum keys with different modulation protocols, meeting the encryption requirements of different channels and users, and improving compatibility with classical optical communication.

[0032] This invention proposes a multi-carrier continuous-variable quantum key distribution system and method, which solves the problems of fiber dispersion effect and data processing performance limitations under ultra-low signal-to-noise ratio in long-distance transmission of high-speed CV-QKD systems. It also enables parallel distribution of continuous-variable quantum keys with different modulation protocols, meeting the encryption requirements of different channels and users, and improving compatibility with classical optical communication. In this invention, "multi-carrier" refers to optical signals with multiple predetermined frequencies.

[0033] A multi-carrier continuous-variable quantum key distribution system includes a multi-carrier quantum key generation module 1, a multi-carrier quantum state preparation module 2, an optical fiber channel 3, a multi-carrier quantum state detection module 4, and a multi-carrier quantum key processing module 5; wherein, the multi-carrier quantum key generation module 1 and the multi-carrier quantum state preparation module 2 are electrically connected, the multi-carrier quantum state preparation module 2, the optical fiber channel 3, and the multi-carrier quantum state detection module 4 are optically connected, and the multi-carrier quantum state detection module 4 and the multi-carrier quantum key processing module 5 are electrically connected.

[0034] The multi-carrier quantum key generation module 1 includes, in sequence, a random number generator 11, a serial-to-parallel conversion submodule 12, a modulation submodule 13 (independent modulation of N subcarriers), a first insertion submodule 14 (inserting training and zero sequences), an inverse Fourier transform submodule 15, a parallel-to-serial conversion submodule 16, a second insertion submodule 17 (inserting cyclic prefix), a first matched filter submodule 18, and a frequency shift submodule 19 (frequency shift f). s ), Real / Imaginary Part Extraction Submodule 110, Digital-to-Analog Converter 111.

[0035] The multi-carrier quantum state preparation module 2 includes an Alice laser 21, a third polarization beam splitter 22, an IQ modulator 23, a first optical attenuator 24, and a polarization combiner 26, all connected by optical fibers. It also includes a second optical attenuator 25, which is optically connected to the third polarization beam splitter 22 and the polarization combiner 26, respectively. The input of the IQ modulator 23 is electrically connected to the output of the digital-to-analog converter 111, and the polarization combiner 26 is optically connected to the optical fiber channel 3.

[0036] The multi-carrier quantum state detection module 4 includes a Bob laser 41, a first polarization beam splitter 42, a first optical coupler 43, a second optical coupler 44, and a second polarization beam splitter 45 connected in sequence by optical fibers. The first polarization beam splitter 42 is optically connected to the first optical coupler 43, the first optical coupler 43 is optically connected to the second polarization beam splitter 45, and the second polarization beam splitter 45 is optically connected to the optical fiber channel 3. It also includes a first balanced detector 46 and a second balanced detector 47. The first optical coupler 43 is optically connected to the first balanced detector 46, and the second optical coupler 44 and the second balanced detector 47 are optically connected.

[0037] The multi-carrier quantum key processing module 5 includes, in sequence, an analog-to-digital converter 51, a frequency offset estimation submodule 52, a bandpass filter submodule 53, a pilot compensation submodule 54, a matched filter submodule 55, a clock synchronization submodule 56, a cyclic prefix removal submodule 57, a second serial-to-parallel transformation submodule 58, a Fourier transform submodule 59, an extraction / removal submodule 510 (extracting training sequences and removing zero sequences), a digital equalization compensation submodule 511 (digital equalization compensation based on training sequences), and a data post-processing submodule 512. The analog-to-digital converter 51 is electrically connected to the first balance detector 46 and the second balance detector 47, respectively.

[0038] A multi-carrier continuous-variable quantum key distribution method is disclosed. A multi-carrier quantum key generation module 1 converts a high-speed quantum key into N orthogonal low-speed quantum key electrical signals, which are then loaded onto a multi-carrier quantum state preparation module 2. In the multi-carrier quantum state preparation module 2, the optical signal output from the Alice laser 21 is split into two signal beams by a third polarization beam splitter 22. One beam undergoes multi-carrier modulation by an IQ modulator 23 and attenuation by a first optical attenuator 24 to form a multi-carrier quantum optical signal. The other beam undergoes a second optical attenuator 25 to form a pilot optical signal. The two optical signals are then transmitted through a polarization beam combiner 26 into an optical fiber channel 3. In a multi-carrier quantum state detection module 4, the optical signal output from the Bob laser 41 is split into two local oscillator beams by a first polarization beam splitter 42, which are coherently detected with the quantum optical signal and the pilot optical signal output from a second polarization beam splitter 45, respectively. A first optical coupler 43 and a first balanced detector 46 are used for coherent detection of the quantum optical signal, while a second optical coupler 44 and a second balanced detector 47 are used for coherent detection of the pilot optical signal. The quantum electrical signal and pilot electrical signal generated by the multi-carrier quantum key detection module enter the multi-carrier quantum key processing module 5 to form N quantum keys.

[0039] Furthermore, the multi-carrier quantum key generation module 1 converts the high-speed quantum key into N orthogonal low-speed quantum key electrical signals, as follows:

[0040] (1) The high-speed true random bit stream generated by high-speed quantum random number generators and other true random number generators is serialized to parallel to form N low-speed true random bit streams.

[0041] (2) The N low-speed true random bit streams are modulated by different Gaussian or discrete modulations to form N quantum key sequences with different modulation distributions. Then, training sequences and zero sequences are inserted into each quantum key sequence for equalization compensation and avoiding inter-symbol interference between quantum key sequences in the multi-carrier quantum key processing module 5, respectively.

[0042] (3) The N-way quantum key sequence with inserted training and zero sequences is transformed into N-way quantum orthogonal subcarriers by inverse Fourier transform, and then transformed into a parallel-to-serial sequence by parallel-prefix insertion and matched filtering to form a quantum key sequence with a sampling rate of f. n A serial signal with N quantum orthogonal subcarriers and bandwidth f;

[0043] (4) The serial signal of N quantum orthogonal subcarriers is frequency-shifted by frequency fs, and then the real and imaginary parts of the signal are extracted and converted into N orthogonal low-speed quantum key electrical signals by digital-to-analog converter.

[0044] Furthermore, the multi-carrier quantum key processing module 5 generates N quantum keys, and the specific process is as follows:

[0045] (1) The quantum electrical signal and pilot electrical signal output by the multi-carrier quantum state detection module 4 are converted into quantum digital signal and pilot digital signal by analog-to-digital converter, and then frequency offset estimation, bandpass filtering and pilot compensation processing are performed. Pilot compensation is to use the pilot digital signal for phase compensation and polarization compensation of quantum digital signal.

[0046] (2) The pilot-compensated quantum digital signal is subjected to matched filtering, clock synchronization, cyclic prefix removal and serial-to-parallel conversion to obtain N quantum orthogonal subcarriers;

[0047] (3) The orthogonality between N quantum orthogonal subcarriers is eliminated by Fourier transform. Then, the training sequence and zero-removed sequence are extracted from each subcarrier. Digital equalization compensation is performed based on the training sequence to eliminate phase, polarization and IQ imbalance noise in the N quantum signals.

[0048] (4) Finally, the N quantum signals are output as the final N quantum keys after data coordination and private key amplification in data post-processing.

[0049] Example 2

[0050] like Figure 1 As shown, as a further optimization of Embodiment 1, this embodiment also includes the following technical features based on Embodiment 1:

[0051] like Figure 1 To achieve a high-performance CV-QKD system with high code rate, long distance, and multi-protocol compatibility, this invention provides a multi-carrier continuous variable quantum key distribution system and method.

[0052] A multi-carrier continuous variable quantum key distribution system includes a multi-carrier quantum key generation module 1, a multi-carrier quantum state preparation module 2, an optical fiber channel 3, a multi-carrier quantum state detection module 4, and a multi-carrier quantum key processing module 5.

[0053] Among them, the multi-carrier quantum key generation module 1 is electrically connected to the multi-carrier quantum state preparation module 2, the multi-carrier quantum state preparation module 2, the optical fiber channel 3 and the multi-carrier quantum state detection module 4 are optically connected, and the multi-carrier quantum state detection module 4 is electrically connected to the multi-carrier quantum key processing module 5.

[0054] The multi-carrier quantum state preparation module 2 includes an Alice laser 21, a third polarization beam splitter 22, an IQ modulator 23, a first optical attenuator 24, a second optical attenuator 25, and a polarization beam combiner 26. The multi-carrier quantum state detection module 4 includes a Bob laser 41, a first polarization beam splitter 42, a second polarization beam splitter 45, a first optical coupler 43, a second optical coupler 44, a first balanced detector 46, and a second balanced detector 47. The splitting ratio of the first polarization beam splitter 42, the second polarization beam splitter 45, and the third polarization beam splitter 22 is 50:50. The coupling ratio of the first optical coupler 43 and the second optical coupler 44 is 50:50. The bandwidth of the first balanced detector 46 and the second balanced detector 47 is generally selected to be twice the repetition frequency of the CV-QKD system. For example, in a CVQKD system with a repetition frequency of 10 GHz, the bandwidth of the first balanced detector 46 and the second balanced detector 47 is selected to be 20 GHz.

[0055] A multi-carrier continuous-variable quantum key distribution method includes the following steps:

[0056] Step 1: In the multi-carrier quantum key generation module 1, the high-speed quantum key is converted into N=5 orthogonal low-speed quantum key electrical signals. The specific process is as follows:

[0057] (1) A high-speed quantum random number generator generates a 320Gbps quantum random bit stream, which is converted into a 64Gbps quantum random bit stream with N=5 channels after serial-to-parallel conversion;

[0058] (2) The N=5 channels of 64Gbps quantum random bit streams are independently Gaussian modulated to form N=5 channels of Gaussian modulated distributed quantum key sequences with a repetition frequency of 2GHz. Then, a training sequence (the ratio of the training sequence to the quantum sequence is 1:4) and a 16-bit zero sequence are inserted into each quantum key sequence, which are used for equalization compensation and avoiding inter-symbol interference between quantum key sequences in the multi-carrier quantum key processing module 5, respectively.

[0059] (3) The N=5 quantum key sequences with inserted training and zero sequences are transformed by inverse Fourier transform to form N=5 quantum orthogonal subcarriers, and then transformed by parallel-to-serial transformation, insertion of cyclic prefix, and matched filtering to form a quantum key sequence with a sampling rate of f. n =30GSa / s and N=5 2GHz quantum orthogonal subcarrier serial signals with a bandwidth of f=13GHz;

[0060] (4) The N=5 quantum orthogonal subcarrier serial signals are frequency-shifted to a frequency of 7GHz, and then the real and imaginary parts are extracted and converted into N=5 orthogonal 2GHz quantum key electrical signals by a digital-to-analog converter (DAC).

[0061] Step 2: The N=5 orthogonal 2GBaud quantum key electrical signals generated by the multi-carrier quantum key generation module 1 are loaded onto the multi-carrier quantum state preparation module 2. In the multi-carrier quantum state preparation module 2, the optical signal output from the Alice laser 21 is split into two signal beams by the third polarization beam splitter 22. One beam is multi-carrier modulated by the IQ modulator 23 and attenuated by the first optical attenuator 24 to form a multi-carrier quantum optical signal. The other beam is piloted by the second optical attenuator 25. The two optical signals are then transmitted into the optical fiber channel 3 via the polarization beam combiner 26.

[0062] Step 3: The multi-carrier quantum optical signal and the classical pilot optical signal reach the multi-carrier quantum state detection module 4 via a 50km optical fiber channel 3. In the multi-carrier quantum state detection module 4, the optical signal output from the Bob laser 41 is split into two local oscillator beams by the first polarization beam splitter 42, which are coherently detected with the quantum optical signal and the pilot optical signal output from the second polarization beam splitter 45 to form a quantum electrical signal. Specifically, the first optical coupler 43 and the first balanced detector 46 are used for the coherent detection of the quantum optical signal to form the pilot electrical signal, while the second optical coupler 44 and the second balanced detector 47 are used for the coherent detection of the pilot optical signal.

[0063] Step 4: The quantum electrical signal and pilot electrical signal generated by the multi-carrier quantum key detection module enter the multi-carrier quantum key processing module 5 to form N=5 quantum keys. The specific process is as follows:

[0064] (1) The quantum electrical signal and pilot electrical signal output by the multi-carrier quantum state detection module 4 are converted into quantum digital signal and pilot digital signal by analog-to-digital converter (ADC), and then frequency offset estimation, bandpass filtering and pilot compensation processing are performed. Pilot compensation is to use the pilot digital signal for phase compensation and polarization compensation of quantum digital signal.

[0065] (2) The pilot-compensated quantum digital signal is subjected to matched filtering, clock synchronization, cyclic prefix removal and serial-to-parallel conversion to obtain N=5 quantum orthogonal subcarriers;

[0066] (3) The orthogonality between the N=5 quantum orthogonal subcarriers is eliminated by Fourier transform. Then, the training sequence and zero-removed sequence are extracted from each subcarrier. Based on the training sequence, digital equalization compensation is performed to eliminate the phase, polarization and IQ imbalance noise in the N=5 quantum signals respectively.

[0067] (4) Finally, the N=5 quantum signals are output as the final N=5 quantum keys after data coordination and private key amplification in the data post-processing.

[0068] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

[0070] The present invention has the following beneficial effects:

[0071] (1) By introducing multi-carrier technology, this invention converts the high-speed CV-QKD system into an N-channel low-speed CV-QKD system, effectively weakening the inter-symbol interference caused by the long-distance fiber dispersion effect of the high-speed CV-QKD system, and effectively improving the transmission distance and security code rate of the CV-QKD system.

[0072] (2) This invention proposes a digital processing algorithm for N-way quantum orthogonal subcarriers, which effectively improves the accuracy of digital signal processing in high-speed, long-distance CV-QKD systems with low signal-to-noise ratio, and ensures the effective realization of high-performance CV-QKD systems;

[0073] (3) By adopting N-way quantum orthogonal subcarrier parallel transmission technology, this invention can realize the parallel distribution of continuous variable quantum keys with different modulation protocols, effectively meet the encryption requirements of different transmission channels and different users, and improve the compatibility of CV-QKD system with classical optical communication system.

[0074] As described above, the present invention can be implemented well.

[0075] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A multi-carrier continuous-variable quantum key distribution system, characterized in that, It includes a multi-carrier quantum key generation module (1), a multi-carrier quantum state preparation module (2), an optical fiber channel (3), a multi-carrier quantum state detection module (4), and a multi-carrier quantum key processing module (5); wherein, the multi-carrier quantum key generation module (1) is electrically connected to the multi-carrier quantum state preparation module (2), the multi-carrier quantum state preparation module (2), the optical fiber channel (3), and the multi-carrier quantum state detection module (4) are sequentially optically connected, and the multi-carrier quantum state detection module (4) is electrically connected to the multi-carrier quantum key processing module (5); The multi-carrier quantum key generation module (1) is used to: convert high-speed quantum keys into N orthogonal low-speed quantum key electrical signals and input them into the multi-carrier quantum state preparation module (2); where N≥2 and N is an integer; The multi-carrier quantum state preparation module (2) is used to: generate multi-carrier quantum optical signals and pilot optical signals, and then send the generated multi-carrier quantum optical signals and pilot optical signals into the optical fiber channel (3) for transmission; The multi-carrier quantum state detection module (4) is used to: receive the multi-carrier quantum optical signal and pilot optical signal transmitted by the optical fiber channel (3), and then perform coherent detection on the multi-carrier quantum optical signal and pilot optical signal to form a multi-carrier quantum electrical signal and a pilot electrical signal; The multi-carrier quantum key processing module (5) is used to: form N quantum keys based on multi-carrier quantum electrical signals and pilot electrical signals; The multi-carrier quantum key generation module (1) includes a random number generator (11), a serial-to-parallel conversion submodule (12), a modulation submodule (13), a first insertion submodule (14), an inverse Fourier transform submodule (15), a parallel-to-serial conversion submodule (16), a second insertion submodule (17), a first matched filter submodule (18), a frequency shift submodule (19), a real / imaginary part extraction submodule (110), and a digital-to-analog converter (111) connected in sequence. The multi-carrier quantum state preparation module (2) includes an Alice laser (21), a third polarization beam splitter (22), an IQ modulator (23), a first optical attenuator (24), and a polarization combiner (26) connected by optical fibers. The multi-carrier quantum state preparation module (2) also includes a second optical attenuator (25) that is optically connected to the third polarization beam splitter (22) and the polarization combiner (26), respectively. The input end of the IQ modulator (23) is electrically connected to the output end of the digital-to-analog converter (111), and the polarization combiner (26) is optically connected to the optical fiber channel (3).

2. The multi-carrier continuous-variable quantum key distribution system according to claim 1, characterized in that, The multi-carrier quantum state detection module (4) includes a Bob laser (41), a first polarization beam splitter (42), a first optical coupler (43), a second optical coupler (44), and a second polarization beam splitter (45) connected in sequence by optical fibers. The first polarization beam splitter (42) is optically connected to the first optical coupler (43), the first optical coupler (43) is optically connected to the second polarization beam splitter (45), and the second polarization beam splitter (45) is optically connected to the optical fiber channel (3). It also includes a first balanced detector (46) and a second balanced detector (47). The first optical coupler (43) is optically connected to the first balanced detector (46), and the second optical coupler (44) and the second balanced detector (47) are optically connected.

3. The multi-carrier continuous-variable quantum key distribution system according to claim 2, characterized in that, The multi-carrier quantum key processing module (5) includes an analog-to-digital converter (51), a frequency offset estimation submodule (52), a bandpass filter submodule (53), a pilot compensation submodule (54), a matched filter submodule (55), a clock synchronization submodule (56), a cyclic prefix removal submodule (57), a second serial-to-parallel conversion submodule (58), a Fourier transform submodule (59), an extraction / removal submodule (510), a digital equalization compensation submodule (511), and a data post-processing submodule (512), which are connected in sequence. The analog-to-digital converter (51) is electrically connected to the first balanced detector (46) and the second balanced detector (47).

4. The multi-carrier continuous-variable quantum key distribution system according to claim 3, characterized in that, The first insertion submodule (14) is used to insert the training sequence and the zero sequence, and the second insertion submodule (17) is used to insert the cyclic prefix.

5. A multi-carrier continuous-variable quantum key distribution system according to claim 4, characterized in that, The extraction / removal submodule (510) is used to extract the training sequence and remove the zero sequence, and the digital equalization compensation submodule (511) is used to implement digital equalization compensation based on the training sequence.

6. A multi-carrier continuous-variable quantum key distribution system according to any one of claims 1 to 5, characterized in that, N=5。 7. A multi-carrier continuous-variable quantum key distribution method, characterized in that, When using the multi-carrier continuous-variable quantum key distribution system according to any one of claims 1 to 6, the following is observed during operation: The multi-carrier quantum key generation module (1) converts the high-speed quantum key into N orthogonal low-speed quantum key electrical signals and inputs them into the multi-carrier quantum state preparation module (2). The multi-carrier quantum state preparation module (2) generates multi-carrier quantum optical signals and pilot optical signals, and then sends the generated multi-carrier quantum optical signals and pilot optical signals into the optical fiber channel (3) for transmission; The multi-carrier quantum state detection module (4) receives the multi-carrier quantum optical signal and pilot optical signal transmitted by the optical fiber channel (3), and then performs coherent detection on the multi-carrier quantum optical signal and pilot optical signal to form a multi-carrier quantum electrical signal and a pilot electrical signal; The multi-carrier quantum key processing module (5) forms N quantum keys based on multi-carrier quantum electrical signals and pilot electrical signals.

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