CN113141253A - Continuous variable quantum key distribution method and system based on thermal state source - Google Patents

Continuous variable quantum key distribution method and system based on thermal state source Download PDF

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CN113141253A
CN113141253A CN202110461910.XA CN202110461910A CN113141253A CN 113141253 A CN113141253 A CN 113141253A CN 202110461910 A CN202110461910 A CN 202110461910A CN 113141253 A CN113141253 A CN 113141253A
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黄鹏
王涛
周颖明
曾贵华
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Shanghai Xuntai Information Technology Co ltd
Shanghai Jiaotong University
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Shanghai Jiaotong University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/548—Phase or frequency modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/70—Photonic quantum communication
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    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0819—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s)
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/12—Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

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  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

The invention provides a continuous variable quantum key distribution method and a system based on a thermal state source, comprising the following steps: the Alice end amplifies the ASE heat state source through an optical amplifier and then passes through a narrow-band optical filter, an optical beam splitter divides the processed ASE heat state source into two paths, one path is processed and then sent to the Bob end of a receiver, and the other path is input into an Alice end optical mixer; the Alice end obtains a processed coherent light source by passing the coherent light source through an attenuator, the optical beam splitter divides the processed coherent light source into two paths, one path is processed and then sent to Bob, and the other path is input into an Alice end optical mixer; performing quantum balance homodyne detection on the Alice-side optical mixer to obtain initial key data K1; the Bob end inputs the received local oscillation signal and the thermal state signal sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control respectively, and initial key data K2 are obtained; and the Bob end processes the obtained initial continuous key data to finally obtain the secure binary bit key.

Description

Continuous variable quantum key distribution method and system based on thermal state source
Technical Field
The invention relates to the technical field of quantum key distribution, in particular to a continuous variable quantum key distribution method and system based on a thermal state source.
Background
Continuous Variable Quantum Key Distribution (CVQKD) allows both parties to a communication separated from both locations, Alice and Bob, to obtain keys over quantum channels and authenticated classical channels. Unlike DVQKD (discrete variable quantum key distribution), in the CVQKD protocol, Alice modulates information onto the regular component of the optical field using gaussian modulation, Bob can extract the key information using a high-efficiency quantum-balanced homodyne or heterodyne detector. The existing security theory has thoroughly proved that the Gaussian modulation coherent CVQKD protocol can resist any collective attack and coherent attack no matter under the condition of distributing key asymptotic limit or considering limited key length. The CVQKD technique does not require a single-photon source and a single-photon detector, and continuous modulation has a larger channel capacity, and it also has better fusion with conventional optical signals, and so on, and is currently receiving wide attention from academia and industry. Commercial products based on the gaussian modulated coherent CVQKD protocol are currently on the market.
However, all the current realization methods of the continuous variable quantum key distribution system modulate and encode the random key information generated by the quantum random number onto the weak coherent light by using the amplitude and phase modulator, for example, gaussian modulation, i.e., the amplitude and phase modulator modulates the quantum random number distributed in gaussian distribution onto the regular component of the weak coherent light, and sends the modulated quantum random number to the receiving party through the optical fiber or the free space channel. Similarly, the discrete modulation CVQKD system implements modulation of a limited number of quantum states by an amplitude and phase modulator, and sends the modulation to a receiver for demodulation and detection. On one hand, the method needs a quantum random number generator and utilizes an active amplitude and phase modulator to realize linear modulation on an optical signal. Then, the actual device and operation state often have non-linear effect, so that the generated initial key information cannot be linearly modulated on the light field component, and the system implementation is complicated.
In order to solve the above problems, we propose a method for integrally implementing continuous variable quantum key distribution based on a thermal state light source, which can match a light field after gaussian modulation of coherent light by using natural fluctuation of thermal light, and can implement continuous variable quantum key distribution based on gaussian modulation, while only increasing part of preparation noises, which can be controlled by controlling average photon number and attenuation coefficient of the thermal state light source. By introducing a bit frame synchronization algorithm without special frame modulation, a high-efficiency negotiation algorithm, a high-bandwidth quantum balance heterodyne detector, high-speed data acquisition and a phase compensation algorithm based on data processing, the CVQKD without quantum random number, intensity and phase modulation can be realized. It is worth noting that: the bit frame synchronization algorithm without special frame modulation, the high-efficiency negotiation algorithm, the high-bandwidth quantum balance heterodyne detector, the high-speed data acquisition and the phase compensation algorithm based on data processing introduced here are not simple superposition, but are comprehensive consideration and technical bottleneck breakthrough of the CVQKD system capable of realizing safe code formation based on a thermal state light source. International CVQKD experimental systems based on thermal state light sources, which can be safely coded under actual transmission channels, have not been reported so far, and one of the fundamental bottlenecks is that after the initial key distribution is completed, no effective bit-frame synchronization method is available to achieve efficient data alignment. The reason is that the existing CVQKD bit frame synchronization method is based on special frame modulation and identification, while the thermal CVQKD method can only realize passive measurement and cannot realize the modulation of special frame data; the other is that the CVQKD over-noise cannot be effectively controlled during the initial key distribution process, including the preparation noise of the CVQKD as a thermal source, and the over-noise introduced by polarization and phase drift during the transmission process of the system, so that the system cannot acquire a secure key at a transmission distance.
In summary, to realize CVQKD based on thermal state light source is not simple module superposition, not only needs to consider high-success rate bit frame synchronization to random initial key data under actual transmission channel, but also needs to suppress over-noise in initial key distribution stage. The bit frame synchronization method without special frame modulation is introduced to realize the synchronization of any continuously distributed random data, the preparation of high-intensity thermal optical state signals can be realized through optical amplification ASE and a DWDM narrow-band filtering method so as to inhibit preparation noise, the phase compensation based on data processing can be realized through the publication of adjacent data bits, and the over-noise introduced by the channel jitter of a CVQKD system is inhibited by combining polarization compensation, so that the continuous variable quantum key distribution in a metropolitan area range under a standard single-mode optical fiber can be finally realized.
Patent document CN109510701A (application No.: 201710843689.8) discloses a continuous variable quantum key distribution (CV-QKD) apparatus and method, the apparatus including: the system comprises a light source, a modulation unit, a first random number generator and a processor; the processor is used for obtaining a first data sequence according to a preset modulation format symbol number, the distribution probability of each symbol and a first random number sequence generated by the first random number generator; obtaining a second data sequence according to the first data sequence; the modulation unit is used for modulating the signal sent by the light source according to the first data sequence and outputting a second optical signal, and the second optical signal does not need to include the number of 28 multiplied by 28 magnitude quantum states required by the existing Gaussian protocol, so that the realization difficulty is low. In addition, the application also provides an EB (Electron Beam) model equivalent to the equipment, and strict safety certification is realized.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a continuous variable quantum key distribution method and system based on a thermal state source.
The invention provides a continuous variable quantum key distribution method based on a thermal state source, which comprises the following steps:
step S1: the Alice end amplifies the ASE hot state source through an optical amplifier and then passes through a narrow-band optical filter to obtain a processed ASE hot state source, the optical beam splitter divides the processed ASE hot state source into two paths, one path of the processed ASE hot state source passes through an optical attenuator and then is sent to the Bob end of a receiving party through a single-mode optical fiber channel, and the other path of the processed ASE hot state source is input into an Alice end optical mixer;
step S2: an Alice end obtains a processed coherent light source by passing the coherent light source through an attenuator, an optical beam splitter divides the processed coherent light source into two paths, one path of coherent light signal is used as a receiving end local oscillation light and sent to Bob through a single-mode optical fiber channel, and the other path of coherent light signal is input into an Alice end optical mixer;
step S3: performing quantum balance homodyne detection on the Alice-side optical mixer to obtain regular components X and P of a thermal state as initial key data K1;
step S4: the Bob end inputs the received local oscillation signals and thermal state signals sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control, and regular components X and P of the received thermal state are obtained and serve as initial key data K2;
step S5: based on the initial continuous secret key data obtained by the Alice terminal, the Bob terminal performs bit frame synchronization, phase compensation, parameter evaluation, error correction and security enhancement on the obtained initial continuous secret key data to finally obtain a secure binary bit secret key.
Preferably, the step S1 includes: the Alice end controls the average photon number by adjusting the ASE light source, the optical amplifier and the optical attenuator, so that the average photon of the thermal state optical signal passing through the optical beam splitter and the optical attenuator meets the condition that n is 0.5mn0Where m denotes the attenuation factor of the optical attenuator and n0The average photon number of the thermal state optical signal after passing through the band-pass filter is represented.
Preferably, the thermal state regularization component in the step S4 includes: the regular component of the thermal state obeys a mean value of zero and a variance of VA＝mn0Of a Gaussian distribution of (a), wherein VAThe value range of (1) satisfies the preset value.
Preferably, the step S5 includes:
step S5.1: the Bob end and the Alice end carry out bit frame synchronization of the initial continuous secret key data without special modulation frames and carry out phase compensation based on data processing;
step S5.2: the method comprises the steps that an Alice end and a Bob end publish part of initial key data to carry out parameter evaluation, and signal noise, modulation variance and channel transmittance parameters are obtained;
step S5.3: the Bob end corrects the error of the initial continuous secret key data after phase compensation through a high-efficiency multidimensional negotiation algorithm based on LDPC coding and outputs a consistent binary system shared secret key string;
step S5.4: and the Bob end calculates the Holevo limit and the mutual information quantity of the legal communication party through the channel parameters to obtain the information compression rate, and finally outputs the final key through privacy enhancement.
Preferably, the method further comprises the following steps: an isolator and a light detector PD are arranged in the optical paths of the Alice end and the Bob end to monitor the light intensity of the thermal state light source and the local oscillation light.
The invention provides a continuous variable quantum key distribution system based on a thermal state source, which comprises:
module M1: the Alice end amplifies the ASE hot state source through an optical amplifier and then passes through a narrow-band optical filter to obtain a processed ASE hot state source, the optical beam splitter divides the processed ASE hot state source into two paths, one path of the processed ASE hot state source passes through an optical attenuator and then is sent to the Bob end of a receiving party through a single-mode optical fiber channel, and the other path of the processed ASE hot state source is input into an Alice end optical mixer;
module M2: an Alice end obtains a processed coherent light source by passing the coherent light source through an attenuator, an optical beam splitter divides the processed coherent light source into two paths, one path of coherent light signal is used as a receiving end local oscillation light and sent to Bob through a single-mode optical fiber channel, and the other path of coherent light signal is input into an Alice end optical mixer;
module M3: performing quantum balance homodyne detection on the Alice-side optical mixer to obtain regular components X and P of a thermal state as initial key data K1;
module M4: the Bob end inputs the received local oscillation signals and thermal state signals sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control, and regular components X and P of the received thermal state are obtained and serve as initial key data K2;
module M5: based on the initial continuous secret key data obtained by the Alice terminal, the Bob terminal performs bit frame synchronization, phase compensation, parameter evaluation, error correction and security enhancement on the obtained initial continuous secret key data to finally obtain a secure binary bit secret key.
Preferably, said module M1 comprises: the Alice end controls the average photon number by adjusting the ASE light source, the optical amplifier and the optical attenuator, so that the average photon of the thermal state optical signal passing through the optical beam splitter and the optical attenuator meets the condition that n is 0.5mn0Where m denotes the attenuation factor of the optical attenuator and n0The average photon number of the thermal state optical signal after passing through the band-pass filter is represented.
Preferably, the hot state regularization component in the module M4 includes: the regular component of the thermal state obeys a mean value of zero and a variance of VA＝mn0Of a Gaussian distribution of (a), wherein VAThe value range of (1) satisfies the preset value.
Preferably, said module M5 comprises:
module M5.1: the Bob end and the Alice end carry out bit frame synchronization of the initial continuous secret key data without special modulation frames and carry out phase compensation based on data processing;
module M5.2: the method comprises the steps that an Alice end and a Bob end publish part of initial key data to carry out parameter evaluation, and signal noise, modulation variance and channel transmittance parameters are obtained;
module M5.3: the Bob end corrects the error of the initial continuous secret key data after phase compensation through a high-efficiency multidimensional negotiation algorithm based on LDPC coding and outputs a consistent binary system shared secret key string;
module M5.4: and the Bob end calculates the Holevo limit and the mutual information quantity of the legal communication party through the channel parameters to obtain the information compression rate, and finally outputs the final key through privacy enhancement.
Preferably further comprising: an isolator and a light detector PD are arranged in the optical paths of the Alice end and the Bob end to monitor the light intensity of the thermal state light source and the local oscillation light.
Compared with the prior art, the invention has the following beneficial effects:
1. the method provided by the invention can realize the CVQKD safe code forming based on the thermal state light source, which is the first international method for realizing the safe code forming under the actual optical fiber channel;
2. the invention utilizes the optical amplifier to amplify the existing ASE heat source and combines with a common single-input single-output Dense Wavelength Division Multiplexer (DWDM) to realize the filtering of the hot-state light source, on one hand, the average photon number of the hot light source is improved to reduce the preparation over-noise introduced by the system, on the other hand, the DWDM narrow-band high extinction ratio characteristic improves the coherence performance and simultaneously reduces the realization complexity and the realization cost;
3. the bit frame synchronization method without special modulation frames does not need special data frame modulation at a sending end, and meets the requirements of CVQKD realization based on a thermal state light source;
4. the phase compensation algorithm based on data processing can utilize the published continuous variable initial key of the adjacent bit to evaluate the phase jitter of the data bit, can greatly reduce the over-noise introduced by the phase jitter, and can ensure the safe code formation in the range of a metropolitan area network;
5. the invention can directly utilize the thermal state light source to realize the distribution of the Gaussian modulation coherent state continuous variable quantum key without an intensity and phase modulator and a random number source, thereby reducing the realization complexity of a continuous variable quantum key distribution system.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram of a continuous variable quantum key distribution method based on a thermal state light source;
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
Example 1
The invention relates to quantum key distribution, in particular to a Continuous Variable Quantum Key Distribution (CVQKD) method based on a thermal state source, and particularly relates to a technology for optimizing a transmitting end information source, coding modulation, bit frame synchronization and over-noise control of the CVQKD, which is used for simplifying and reducing the cost of the existing Gaussian modulation coherent state CVQKD system and the realization thereof, and simultaneously improving the safety code rate performance of the CVQKD at a short distance. The method utilizes the natural true randomness of the thermal state regular component to realize the Gaussian randomness coding of the non-reciprocal light field component in the continuous variable quantum cryptography communication, but only equivalently increases the preparation noise of part of coding signals, and can realize the distribution of the high-code-rate continuous variable quantum key without a true random number generator and a Gaussian modulation method.
The invention provides a continuous variable quantum key distribution method based on a thermal state source, which comprises the following steps:
step S1: the Alice end amplifies the ASE hot state source through an optical amplifier and then passes through a narrow-band optical filter to obtain a processed ASE hot state source, the optical beam splitter divides the processed ASE hot state source into two paths, one path of the processed ASE hot state source passes through an optical attenuator and then is sent to the Bob end of a receiving party through a single-mode optical fiber channel, and the other path of the processed ASE hot state source is input into an Alice end optical mixer;
step S2: an Alice end obtains a processed coherent light source by passing the coherent light source through an attenuator, an optical beam splitter divides the processed coherent light source into two paths, one path of coherent light signal is used as a receiving end local oscillation light and sent to Bob through a single-mode optical fiber channel, and the other path of coherent light signal is input into an Alice end optical mixer;
step S3: performing quantum balance homodyne detection on the Alice-side optical mixer to obtain regular components X and P of a thermal state as initial key data K1;
step S4: the Bob end inputs the received local oscillation signals and thermal state signals sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control, and regular components X and P of the received thermal state are obtained and serve as initial key data K2;
step S5: based on the initial continuous secret key data obtained by the Alice terminal, the Bob terminal performs bit frame synchronization, phase compensation, parameter evaluation, error correction and security enhancement on the obtained initial continuous secret key data to finally obtain a secure binary bit secret key.
Specifically, the step S1 includes: the Alice end controls the average photon number by adjusting the ASE light source, the optical amplifier and the optical attenuator, so that the average photon of the thermal state optical signal passing through the optical beam splitter and the optical attenuator meets the condition that n is 0.5mn0Where m denotes the attenuation factor of the optical attenuator and n0The average photon number of the thermal state optical signal after passing through the band-pass filter is represented.
Specifically, the hot state regularization component in step S4 includes: the regular component of the thermal state obeys a mean value of zero and a variance of VA＝mn0Of a Gaussian distribution of (a), wherein VAThe value range of (1) satisfies the preset value.
Specifically, the step S5 includes:
step S5.1: the Bob end and the Alice end carry out bit frame synchronization of the initial continuous secret key data without special modulation frames and carry out phase compensation based on data processing;
step S5.2: the method comprises the steps that an Alice end and a Bob end publish part of initial key data to carry out parameter evaluation, and signal noise, modulation variance and channel transmittance parameters are obtained;
step S5.3: the Bob end corrects the error of the initial continuous secret key data after phase compensation through a high-efficiency multidimensional negotiation algorithm based on LDPC coding and outputs a consistent binary system shared secret key string;
step S5.4: and the Bob end calculates the Holevo limit and the mutual information quantity of the legal communication party through the channel parameters to obtain the information compression rate, and finally outputs the final key through privacy enhancement.
Specifically, the method further comprises the following steps: an isolator and a light detector PD are arranged in the optical paths of the Alice end and the Bob end to monitor the light intensity of the thermal state light source and the local oscillation light.
According to the present invention, a continuous variable quantum key distribution system based on a thermal state source is provided, as shown in fig. 1, including:
module M1: the Alice end amplifies the ASE hot state source through an optical amplifier and then passes through a narrow-band optical filter to obtain a processed ASE hot state source, the optical beam splitter divides the processed ASE hot state source into two paths, one path of the processed ASE hot state source passes through an optical attenuator and then is sent to the Bob end of a receiving party through a single-mode optical fiber channel, and the other path of the processed ASE hot state source is input into an Alice end optical mixer;
module M2: an Alice end obtains a processed coherent light source by passing the coherent light source through an attenuator, an optical beam splitter divides the processed coherent light source into two paths, one path of coherent light signal is used as a receiving end local oscillation light and sent to Bob through a single-mode optical fiber channel, and the other path of coherent light signal is input into an Alice end optical mixer;
module M3: performing quantum balance homodyne detection on the Alice-side optical mixer to obtain regular components X and P of a thermal state as initial key data K1;
module M4: the Bob end inputs the received local oscillation signals and thermal state signals sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control, and regular components X and P of the received thermal state are obtained and serve as initial key data K2;
module M5: based on the initial continuous secret key data obtained by the Alice terminal, the Bob terminal performs bit frame synchronization, phase compensation, parameter evaluation, error correction and security enhancement on the obtained initial continuous secret key data to finally obtain a secure binary bit secret key.
Specifically, the module M1 includes: the Alice end controls the average photon number by adjusting the ASE light source, the optical amplifier and the optical attenuator, so that the average photon of the thermal state optical signal passing through the optical beam splitter and the optical attenuator meets the condition that n is 0.5mn0Where m denotes the attenuation factor of the optical attenuator and n0The average photon number of the thermal state optical signal after passing through the band-pass filter is represented.
Specifically, the hot state regularization component in the module M4 includes: the regular component of the thermal state obeys a mean value of zero and a variance of VA＝mn0Of a Gaussian distribution of (a), wherein VAThe value range of (1) satisfies the preset value.
Specifically, the module M5 includes:
module M5.1: the Bob end and the Alice end carry out bit frame synchronization of the initial continuous secret key data without special modulation frames and carry out phase compensation based on data processing;
module M5.2: the method comprises the steps that an Alice end and a Bob end publish part of initial key data to carry out parameter evaluation, and signal noise, modulation variance and channel transmittance parameters are obtained;
module M5.3: the Bob end corrects the error of the initial continuous secret key data after phase compensation through a high-efficiency multidimensional negotiation algorithm based on LDPC coding and outputs a consistent binary system shared secret key string;
module M5.4: and the Bob end calculates the Holevo limit and the mutual information quantity of the legal communication party through the channel parameters to obtain the information compression rate, and finally outputs the final key through privacy enhancement.
Specifically, the method further comprises the following steps: an isolator and a light detector PD are arranged in the optical paths of the Alice end and the Bob end to monitor the light intensity of the thermal state light source and the local oscillation light.
Example 2
Example 2 is a preferred example of example 1
Aiming at the defects in the prior art, the invention aims to provide a continuous variable quantum key distribution method based on a thermal state light source, which is used for simplifying and reducing the cost of the existing Gaussian modulation coherent state CVQKD system and the realization thereof through the technologies of optimizing a transmitting end information source, coding modulation, bit frame synchronization and over-noise control of the CVQKD. The method can be used for high-speed quantum key distribution under the metro scale and can be effectively used for realizing the CVQKD of the integrated chip.
The invention provides a continuous variable quantum key distribution method based on a thermal state light source, which comprises the following steps:
step A: the method comprises the following steps of distributing continuous variable initial keys: the method comprises the steps that a sender Alice uses detection results of regular components X and P after splitting of a thermal state source as a local initial secret key, and detects a receiver Bob after the other half of a thermal state optical signal is attenuated and transmitted through an optical fiber channel to obtain corresponding initial continuous secret key data;
and B: the continuous data post-processing steps specifically include: bob carries out bit frame synchronization, phase compensation, parameter evaluation, error correction and security enhancement on the obtained initial continuous key data, and finally obtains a secure binary bit key.
Specifically, the step a includes the steps of:
step A1: a sender Alice and a receiver Bob perform communication initialization on a Continuous Variable Quantum Key Distribution (CVQKD) system based on a thermal state light source, as shown in fig. 1, ase (amplified spontaneous emission) is an amplified spontaneous emission heat source, a 90 ° Hybrid is an optical Hybrid, and two 50:50 beam splitters are included inside the system, and respectively divide two input optical signals into two paths, wherein the phase of one optical signal output by one signal beam splitter rotates by 90 °, the phase of the other beam splitter output does not change, and Hom is a quantum balance homodyne detector. Further comprising: initializing a coherent light source, an optical amplifier, an optical band-pass filter and a control circuit;
step A2: the Alice end amplifies the ASE heat state source through an optical amplifier, then the amplified ASE heat state source passes through a narrow-band optical filter and passes through a 50: the 50 optical beam splitter divides the data into two paths, one path is transmitted to a receiving party Bob through a single-mode optical fiber channel after passing through the optical attenuator, the other path is left locally, and is simultaneously input into an optical mixer with a coherent light source after passing through the attenuator and a part of local oscillation signals of the 50:50 optical beam splitter for quantum balance homodyne detection, and meanwhile, regular components X and P in a thermal state are obtained to serve as initial key data K1. The other half of the coherent light signal is used as a receiving end local oscillator light and sent to Bob through another single-mode optical fiber channel;
step A3: bob inputs the received local oscillation signal and the thermal state signal sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control, and obtains regular components X and P of the received thermal state as initial key data K2.
Specifically, the hot-state source can realize filtering of the hot-state light source by utilizing the existing ASE heat source and combining with a common single-input single-output Dense Wavelength Division Multiplexer (DWDM), so that on one hand, the average photon number of the hot-state light source is improved, and on the other hand, the implementation complexity of the hot-state light source is reduced while the coherence performance is improved by the narrow-band high extinction ratio characteristic of the DWDM. In addition, because two optical fibers are used for respectively transmitting the thermal state signal and the local oscillation signal, the mode of time division, wavelength division and polarization multiplexing is not needed, pulse modulation is not needed, Alice and Bob can realize the interference of continuous thermal state signals and continuous coherent optical signals, and initial key data is acquired at high speed by utilizing high-bandwidth quantum balance heterodyne detection and a high-bandwidth data acquisition card, so that the distribution of the high-code-rate continuous variable quantum key is realized.
The high bandwidth quantum balance homodyne detector is prior art, such as PDB435C, a product of Thorlabs, inc;
the ASE is the prior art, such as the product ASE Light Source of Goight corporation;
the optical amplifier is the prior art, such as KY-EDFA-0-30-D-FA which is a product of Keyangphotoelectricity company;
the optical amplifier is a prior art, such as product C34 DWDM of keyan optical company.
Specifically, the step a2 includes the following steps:
step A2.1: alice performs average photon number control by adjusting the ASE light source, optical amplifier, and optical attenuator, such that the ratio of 50:50 the average photon number of the hot state optical signal light of the optical beam splitter and the attenuator satisfies that n is 0.5mn0Wherein m is attenuation factor of the optical attenuator, n0 is average photon number of the thermal state optical signal after passing through the band-pass filter, the mean value of the thermal state regular component is zero, and the variance is VA＝mn0Is a Gaussian distribution of where VAThe value range of (a) is more than 0 and less than 80, and the value range of (b) is sent to Bob through a single-mode fiber channel;
step A2.2: alice keeps the other half of the thermal optical signals split by the 50:50 optical beam splitter local, and after controlling the light intensity with the continuous coherent optical signals generated by Alice through the optical attenuator, part of the optical signals split by the 50:50 optical beam splitter are simultaneously input into the Hybrid mixer to realize the interference of two paths of continuous optical signals, and the initial key data X (which are the values of the regular components X and P of the thermal state optical signals) is obtained through the quantum balance homodyne detector, and the other path of optical fiber is sent to Bob.
Specifically, the step B includes the steps of:
step B1: bob and Alice perform bit frame synchronization of the initial continuous key data without special modulation frames, and perform phase compensation based on data processing;
the bit frame synchronization without special modulation frame can be realized by a person skilled in the art by learning the prior art, for example, the bit frame synchronization without special modulation frame can be realized by referring to a "bit frame synchronization method and system without special frame of a quantum key distribution system" (application number: 2019106418841, publication number: CN110213034A) disclosed in the patent document of the invention of china, and in the patent document, "bit frame synchronization without special modulation frame" is referred to as a "bit frame synchronization method without special frame of a quantum key distribution system";
the phase compensation based on data processing can be realized by learning the prior art by those skilled in the art, for example, the phase compensation based on data processing can be realized by referring to the "phase compensation method of quantum key distribution system" (application No. 201410567665.0, publication No. CN104301101A) disclosed in the patent document of china invention, in which the "phase compensation based on data processing" is referred to as "phase compensation of quantum key distribution system".
Step B2: alice and Bob publish part of initial key data to perform parameter evaluation to obtain signal noise, modulation variance and channel transmittance parameters;
step B3: bob corrects the error of the initial continuous secret key data after phase compensation through a high-efficiency multidimensional negotiation algorithm based on LDPC coding, and outputs a consistent binary system shared secret key string;
wherein, the efficient Multidimensional negotiation algorithm based on LDPC coding is prior art, and those skilled in the art can implement the efficient Multidimensional negotiation algorithm based on LDPC coding by learning prior art, for example, learning the paper "a.levirrier, et al, Multidimensional negotiation for a connected-variable quality distribution.phys.rev.a 77(4),042325 (2008)", in this paper document, "efficient Multidimensional negotiation algorithm based on LDPC coding" is called "Multidimensional negotiation".
Step B4: bob calculates the Holevo limit and the mutual information quantity of the legal communication party through channel parameters to obtain the information compression rate, and finally outputs the final key through privacy enhancement.
The method of said calculation is a well-known technique, for example the person skilled in the art can carry out said calculation by referring to the paper "Weedbrook, c.et al.
Specifically, an isolator and a photodetector PD are disposed in the optical paths of Alice and Bob to monitor the intensity of the thermal state light source and the local oscillation light.
Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered to be both software programs for performing the methods and structures within hardware components.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (10)

1. A continuous variable quantum key distribution method based on a thermal state source is characterized by comprising the following steps:
step S1: the Alice end amplifies the ASE hot state source through an optical amplifier and then passes through a narrow-band optical filter to obtain a processed ASE hot state source, the optical beam splitter divides the processed ASE hot state source into two paths, one path of the processed ASE hot state source passes through an optical attenuator and then is sent to the Bob end of a receiving party through a single-mode optical fiber channel, and the other path of the processed ASE hot state source is input into an Alice end optical mixer;
step S2: an Alice end obtains a processed coherent light source by passing the coherent light source through an attenuator, an optical beam splitter divides the processed coherent light source into two paths, one path of coherent light signal is used as a receiving end local oscillation light and sent to Bob through a single-mode optical fiber channel, and the other path of coherent light signal is input into an Alice end optical mixer;
step S3: performing quantum balance homodyne detection on the Alice-side optical mixer to obtain regular components X and P of a thermal state as initial key data K1;
step S4: the Bob end inputs the received local oscillation signals and thermal state signals sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control, and regular components X and P of the received thermal state are obtained and serve as initial key data K2;
step S5: based on the initial continuous secret key data obtained by the Alice terminal, the Bob terminal performs bit frame synchronization, phase compensation, parameter evaluation, error correction and security enhancement on the obtained initial continuous secret key data to finally obtain a secure binary bit secret key.
2. The method for continuous variable quantum key distribution based on thermal state source according to claim 1, wherein the step S1 comprises: the Alice end controls the average photon number by adjusting the ASE light source, the optical amplifier and the optical attenuator, so that the average photon of the thermal state optical signal passing through the optical beam splitter and the optical attenuator meets the condition that n is 0.5mn0Where m denotes the attenuation factor of the optical attenuator and n0The average photon number of the thermal state optical signal after passing through the band-pass filter is represented.
3. The method for continuous variable quantum key distribution based on thermal state source according to claim 1, wherein the thermal state regular component in step S4 comprises: the regular component of the thermal state obeys a mean value of zero and a variance of VA＝mn0Of a Gaussian distribution of (a), wherein VAThe value range of (1) satisfies the preset value.
4. The method for continuous variable quantum key distribution based on thermal state source according to claim 1, wherein the step S5 comprises:
step S5.1: the Bob end and the Alice end carry out bit frame synchronization of the initial continuous secret key data without special modulation frames and carry out phase compensation based on data processing;
step S5.2: the method comprises the steps that an Alice end and a Bob end publish part of initial key data to carry out parameter evaluation, and signal noise, modulation variance and channel transmittance parameters are obtained;
step S5.3: the Bob end corrects the error of the initial continuous secret key data after phase compensation through a high-efficiency multidimensional negotiation algorithm based on LDPC coding and outputs a consistent binary system shared secret key string;
step S5.4: and the Bob end calculates the Holevo limit and the mutual information quantity of the legal communication party through the channel parameters to obtain the information compression rate, and finally outputs the final key through privacy enhancement.
5. The method for continuous variable quantum key distribution based on thermal state source according to claim 1, further comprising: an isolator and a light detector PD are arranged in the optical paths of the Alice end and the Bob end to monitor the light intensity of the thermal state light source and the local oscillation light.
6. A system for continuous variable quantum key distribution based on a thermal state source, comprising:
module M1: the Alice end amplifies the ASE hot state source through an optical amplifier and then passes through a narrow-band optical filter to obtain a processed ASE hot state source, the optical beam splitter divides the processed ASE hot state source into two paths, one path of the processed ASE hot state source passes through an optical attenuator and then is sent to the Bob end of a receiving party through a single-mode optical fiber channel, and the other path of the processed ASE hot state source is input into an Alice end optical mixer;
module M2: an Alice end obtains a processed coherent light source by passing the coherent light source through an attenuator, an optical beam splitter divides the processed coherent light source into two paths, one path of coherent light signal is used as a receiving end local oscillation light and sent to Bob through a single-mode optical fiber channel, and the other path of coherent light signal is input into an Alice end optical mixer;
module M3: performing quantum balance homodyne detection on the Alice-side optical mixer to obtain regular components X and P of a thermal state as initial key data K1;
module M4: the Bob end inputs the received local oscillation signals and thermal state signals sent by Alice into an optical mixer for quantum balance homodyne detection after polarization control, and regular components X and P of the received thermal state are obtained and serve as initial key data K2;
module M5: based on the initial continuous secret key data obtained by the Alice terminal, the Bob terminal performs bit frame synchronization, phase compensation, parameter evaluation, error correction and security enhancement on the obtained initial continuous secret key data to finally obtain a secure binary bit secret key.
7. The system according to claim 6, wherein the module M1 comprises: the Alice end controls the average photon number by adjusting the ASE light source, the optical amplifier and the optical attenuator, so that the average photon of the thermal state optical signal passing through the optical beam splitter and the optical attenuator meets the condition that n is 0.5mn0Where m denotes the attenuation factor of the optical attenuator and n0The average photon number of the thermal state optical signal after passing through the band-pass filter is represented.
8. The system according to claim 6, wherein the thermal state regular components in the module M4 comprise: the regular component of the thermal state obeys a mean value of zero and a variance of VA＝mn0Of a Gaussian distribution of (a), wherein VAThe value range of (1) satisfies the preset value.
9. The system according to claim 6, wherein the module M5 comprises:
module M5.1: the Bob end and the Alice end carry out bit frame synchronization of the initial continuous secret key data without special modulation frames and carry out phase compensation based on data processing;
module M5.2: the method comprises the steps that an Alice end and a Bob end publish part of initial key data to carry out parameter evaluation, and signal noise, modulation variance and channel transmittance parameters are obtained;
module M5.3: the Bob end corrects the error of the initial continuous secret key data after phase compensation through a high-efficiency multidimensional negotiation algorithm based on LDPC coding and outputs a consistent binary system shared secret key string;
module M5.4: and the Bob end calculates the Holevo limit and the mutual information quantity of the legal communication party through the channel parameters to obtain the information compression rate, and finally outputs the final key through privacy enhancement.
10. The system according to claim 6, further comprising: an isolator and a light detector PD are arranged in the optical paths of the Alice end and the Bob end to monitor the light intensity of the thermal state light source and the local oscillation light.
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