CN112994877A - Quantum key distribution system and method based on quantum random number - Google Patents
Quantum key distribution system and method based on quantum random number Download PDFInfo
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Abstract
The invention discloses a quantum key distribution system and method based on quantum random numbers, belongs to the technical field of quantum communication, and is characterized in that on the basis of a quantum key distribution system of a conventional Faraday-Michelson interferometer, an optical switch is used for carrying out light path control, a random number generation module is used for generating random bit strings, and the quantum key distribution system based on the quantum random numbers is constructed. Compared with the traditional F-M system, the invention can be used for long-distance optical quantum communication, has strong anti-interference capability, can effectively avoid the safety problem caused by random number leakage, and provides further guarantee for the safe operation of the smart grid.
Description
Technical Field
The invention discloses a quantum key distribution system and method based on quantum random numbers, and belongs to the technical field of quantum secret communication.
Background
The quantum secret communication technology is rapidly developed by a unique secret key security distribution mechanism and gradually goes to commercial use. The absolute security of quantum secret communication is strictly proved in principle, and the security problem of data encryption transmission can be solved. Compared with a classical communication mode, quantum secret communication is not easy to crack, any operation of trying to steal information can be found immediately, and the quantum secret communication is applied to various social fields in a large scale to guarantee the safety of information transmission. The quantum secret communication combines a quantum technology with the existing information secret system, greatly improves the security level of data protection, and effectively ensures the secure transmission of information.
According to the classical information theory, the absolute communication security can be realized by adopting a symmetric encryption scheme of 'one-time pad', and even a quantum computer cannot threaten the absolute communication security. The scheme requires that two communication parties carry out Key Distribution before communication, the security of the Key is difficult to guarantee through classical Key Distribution, and the Quantum Key Distribution (QKD) has unconditional security, and the security depends on the basic principle of Quantum mechanics. The well-known QKD protocols include BB84 protocol, B92 protocol, and the like. These protocols all contain the step of randomly selecting the measurement base, so that the generation of random numbers is necessarily involved in the protocol process.
The generation of random numbers must satisfy unpredictability, which is not guaranteed by classical mechanics. In classical calculations, the random number is generated by a particular generation algorithm and a random seed, and once the algorithm flow and the random seed are determined, the value it generates can also be determined. Thus, classical random numbers are theoretically predictable, which can create a safety hazard in some applications. For example, in the BB84 protocol, an eavesdropper, if it obtains the random number generated by the sender, will be able to obtain the complete key information without being discovered. Quantum mechanics has inherent randomness, and devices that utilize Quantum randomness to generate Random numbers are known as Quantum Random Number Generators (QRNGs), which are physically unpredictable compared to classical Random Number generators. Current QRNG implementations rely primarily on optical systems, such as based on photon counting, based on photon arrival time, based on photon arrival location, and the like.
Disclosure of Invention
The invention provides a quantum key distribution system and a method based on quantum random numbers, which are an improvement on an F-M system and have higher safety in the aspect of random number generation.
The technical scheme adopted by the invention is as follows:
the invention provides a quantum key distribution system based on quantum random number, comprising: an F-M system and a random number generation module;
the random number generation module is used for generating a random bit string;
the F-M system is used for carrying out quantum state modulation on a laser light source by adopting the random bit string to generate and distribute a quantum key;
the F-M system comprises a laser diode, an optical attenuator, a coupler C1 and a coupler C2;
the output end of the laser diode is provided with an optical switch S1, the input end of the optical attenuator is provided with a port P1, the input end of a coupler C1 is provided with a port P2, the output end of the optical attenuator is provided with an optical switch S2, and the input end of a coupler C2 is provided with a port P3;
the input end of the random number generation module is provided with a port P4;
in the random number generation stage of the quantum key distribution system, the optical switch S1 is communicated with the port P1, and the optical switch S2 is communicated with the port P4;
in the quantum key distribution system, in the key distribution stage, the optical switch S1 is communicated with the port P2, and the optical switch S2 is communicated with the port P3.
Further, the F-M system also comprises a sender main control module, a receiver main control module, a rotating mirror FM1, a rotating mirror FM2, a rotating mirror FM3, a rotating mirror FM4, a phase modulator PMa, a phase modulator PMb and a single photon avalanche diode;
the laser diode is used for outputting continuous laser;
the optical attenuator is used for reducing the intensity of the received light beam to a level that the average number of photons arriving in each time interval T is less than 1;
the rotating mirror FM1 is used for reflecting the pulse transmitted along the short arm and separated by the coupler C1 back to the coupler C1;
the phase modulator PMa is used for modulating the pulse transmitted along the long arm and branched by the coupler C1;
the rotating mirror FM2 is used for reflecting the pulse modulated by the phase modulator PMa back to the coupler C1;
the coupler C1 is used for dividing the laser emitted by the laser diode into two beams and coupling the two reflected beams;
the coupler C2 is used for dividing the pulse sent by the optical attenuator into two beams; coupling the two reflected laser beams;
the rotating mirror FM3 is used for reflecting the pulse transmitted along the short arm and separated by the coupler C2 back to the coupler C2;
the phase modulator PMb is used for modulating the pulse transmitted along the long arm and branched by the coupler C2;
the rotating mirror FM4 is used for reflecting the pulse modulated by the phase modulator PMb back to the coupler C2;
the single photon avalanche diode is used for detecting the pulse emitted by the coupler C2;
the sender main control module is used for controlling the on-off of the optical switch and the port and controlling the modulation of the quantum state of the laser light source;
and the receiver main control module is used for controlling the measurement of the received laser quantum state.
Further, the sender main control module is specifically configured to,
in the random number generation phase, the optical switch S1 is controlled to be communicated with the port P1, and the optical switch S2 is controlled to be communicated with the port P4;
during the key distribution phase, optical switch S1 is controlled to communicate with port P2, and optical switch S2 communicates with port P3.
Further, the sender main control module is specifically configured to,
and calling the random bit string generated by the random number generation module to modulate the quantum state of the laser light source.
Further, the optical attenuator is particularly useful for,
when the optical switch S1 is communicated with the port P1, the intensity of the laser light emitted by the laser diode is reduced to a level that the average photon number arriving in each time interval is less than 1;
when the optical switch S1 is in communication with port P2, the pulses coupled by coupler C1 are dropped to a level where the average number of photons arriving in each time interval is less than 1.
Further, the receiving side main control module is specifically configured to,
measuring the quantum state detected by the single photon avalanche diode;
and comparing the basis vectors of the measurement results through a classical channel to obtain the screened key.
Further, the optical switch S1 and the optical switch S2 are mechanical optical switches.
Further, the random number generation module includes: a built-in signal source Ref, a single photon avalanche diode, a digital time converter and an FPGA;
the single photon avalanche diode is used for detecting photons emitted by the optical attenuator and generating a pulse signal;
the built-in signal source Ref is used for generating a reference signal with a period T;
the digital time converter is used for receiving a pulse signal generated by the single photon avalanche diode as a stop signal and receiving a reference signal generated by a built-in signal source Ref as a start signal;
the FPGA is used for generating original random bits according to the output of the digital-to-time converter and extracting a final random bit string by adopting a Toplitz matrix.
The invention also provides a quantum key distribution method based on the quantum random number, which comprises the following steps:
controlling an optical switch S1 to be communicated with a port P1 and S2 to be communicated with a port P4 in the quantum key distribution system;
controlling the laser diode to emit continuous laser and entering the optical attenuator;
reducing the intensity of the received laser beam to the level that the average photon number arriving in each time interval T is less than 1, and transmitting the laser beam to a random number generation module to generate a random bit string;
calling a random bit string generated by a random number generation module to carry out quantum state modulation on a laser light source emitted by a laser diode;
controlling an optical switch S1 to be communicated with a port P2 and S2 to be communicated with a port P3 in the quantum key distribution system;
the modulated quantum state enters a coupler C1 and is divided into two pulses which are transmitted along the short arm and two pulses which are transmitted along the long arm;
the pulse transmitted along the short arm is reflected to the coupler C1 through the rotating mirror FM1, and the pulse transmitted along the long arm is modulated by the phase modulator PMa and then reflected to the coupler C1 through the rotating mirror FM 2;
the two pulses entering the coupler C1 are coupled in a quantum channel and sent to the coupler C2, and are divided into two pulses which are transmitted along the short arm and two pulses which are transmitted along the long arm;
the pulse modulated by the phase modulator PMa is transmitted along the short arm and reflected to the coupler C2 through the rotating mirror FM3, and the pulse not modulated is transmitted along the long arm and reflected to the coupler C2 through the rotating mirror FM4 after being modulated by the phase modulator PMb;
the two pulses entering coupler C2 are coupled in a quantum channel and detected by a single photon avalanche diode;
and measuring the detected quantum state and screening out the key.
Further, the random number generation module generates a random bit string, including:
the single photon avalanche diode detects photons emitted by the optical attenuator and generates a pulse signal, and a built-in signal source Ref generates a reference signal with a period T;
the digital time converter receives a pulse signal generated by the single photon avalanche diode as a stop signal, receives a reference signal generated by a built-in signal source Ref as a start signal, and generates and outputs the start signal;
the FPGA takes the output of the digital-to-time converter as input and generates an original random bit string.
Furthermore, the method also comprises the following steps of,
the Toplitz matrix is used to extract the final random bit string from the original random bit string.
The invention achieves the following beneficial effects:
the invention provides a quantum key distribution system and method based on quantum random numbers, which are characterized in that on the basis of the quantum key distribution system of the conventional Faraday-Michelson interferometer, an optical switch is used for light path control, and a random number generation module is used for generating random bit strings. Compared with the traditional F-M system, the invention can be used for long-distance optical quantum communication, has strong anti-interference capability, can effectively avoid the safety problem caused by random number leakage, and provides further guarantee for the safe operation of the smart grid.
Drawings
FIG. 1 is a F-M system architecture;
FIG. 2 is a schematic diagram of the randomness of photon arrival times in a Poisson distribution;
fig. 3 is a QRNG structure based on photon arrival times;
FIG. 4 is an optical switch architecture for use with the system of the present invention;
FIG. 5 is a block diagram of a random number generation module according to the present invention;
fig. 6 is the overall structure of the QRNG-based quantum key distribution system of the present invention.
Detailed Description
The following describes the embodiments in further detail with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
(1) F-M system
The quantum key distribution is realized without the support of a hardware system, and Mo and the like propose and realize a quantum key distribution system based on a Faraday-Michelson interferometer in 2005, which is referred to as an F-M system for short. The system can automatically compensate polarization change caused by environmental disturbance, and effectively eliminate the influence of the polarization state on the stability of the quantum key distribution system in long-distance transmission.
The structure of the F-M system is shown in FIG. 1. A laser pulse emitted by a Laser Diode (LD) is split into two pulses by a coupler C1. The pulses transmitted along the short arm are reflected by the Faraday rotator FM1 and returned to C1, while the pulses along the long arm are modulated by the phase modulator PMa and reflected by the Faraday rotator FM2 and returned to the coupler C1 after a certain time delay DL 1. Two pulses are coupled in a quantum channel and sent to Bob, the pulses are divided into two groups again after reaching a coupler C2, the pulses which are modulated by Alice end PMa are transmitted along the short arm and reflected by a Faraday rotating mirror FM3 and returned to C2, the pulses which are not modulated are transmitted along the long arm and modulated by a phase modulator PMb and reflected by a Faraday rotating mirror FM4, and DL2 returns to a coupler C2 after a certain time delay. Since DL1 is delayed by the same time as DL2, two pulses modulated only once by PMb will arrive at coupler C2 at the same time and interfere, and then be detected by a single-photon avalanche diode (SPAD). By controlling PMa and PMb, Alice and Bob can complete a single photon based quantum key distribution protocol, such as the BB84 protocol.
(2) QRNG based on photon arrival time
During a time interval T, the number of photons n of the continuous laser follows a poisson distribution with a parameter λ, as shown by the formula:
according to the nature of the poisson distribution, for a photon arriving within the time interval (T, T + T), the probability of its arrival at each time instant is equal. As shown in fig. 2, a pulse signal with a period T is used as a reference signal, and the relative arrival time of photons in each time interval is denoted as TrThen t isrObeying a uniform distribution over (0, T). The time interval T is divided into N intervals { tau }1,τ2,...,τNIs then according to trThe interval in which the random number is located can be a random number in {1, 2.. multidot.N }.
Nie et al proposed a QRNG implementation based on photon arrival time in 2014, whose structure is shown in FIG. 3. The continuous laser light emitted by the laser diode LD passes through an optical Attenuator (ATT) whose intensity drops to a level where the average number of photons arriving in each time interval T is less than 1. A single-photon avalanche diode (SPAD) is capable of detecting the arrival of a photon and generating a pulse signal as a stop signal for a digital-to-digital converter (TDC), and an external periodic pulse signal with a period T as a start signal for the TDC. The output of the TDC is used as the input of a Field Programmable Gate Array (FPGA), and finally, an original random bit string is output. The original random bit string has a slight deviation from the uniform distribution, and an ideal uniformly distributed bit string can be obtained by performing certain post-processing on a computer.
The photon arrival time-based QRNG described above can significantly eliminate bias in experimental data, generating an almost uniformly distributed original random bit string. Compared with other optical-based QRNG implementation schemes, the method has the advantages of high random number generation rate and simple equipment, and therefore has higher practicability. Unless otherwise specified, all references to QRNGs in the present invention are to QRNGs based on the time of arrival of a photon.
(3) Optical switch design
The optical path control of the quantum key distribution system is realized by adopting a mechanical optical switch, and the propagation path of light can be selected and switched. The mechanical optical switch has the characteristics of low insertion loss, high isolation, long service life, small size and the like, and can realize dynamic switching between any two quantum links, as shown in fig. 4, when the optical switch is connected with an upper line, the port P1 is communicated with the port P2, and when the optical switch is connected with a lower line, the port P1 is communicated with the port P3.
(4) Random number generation module design
The QRNG based on photon arrival time has a key task of converting a physical quantity with randomness, namely "photon arrival time", into a random number, and a module for completing the task is called a Random Number Generation Module (RNGM), and has a structure shown in fig. 5, and includes a built-in signal source Ref, a single photon avalanche diode SPAD, a digital time converter TDC, and an FPGA.
Specifically, the single photon avalanche diode SPAD is used for detecting photons and generating a pulse signal;
the built-in signal source Ref is used for generating a reference signal with a period T;
the digital time converter TDC is used for receiving a pulse signal generated by the single photon avalanche diode SPAD as a stop signal and receiving a reference signal generated by a built-in signal source Ref as a start signal;
the FPGA is used for generating original random bits according to the output signal of the TDC.
The working principle of the random number generation module is as follows:
the input of the module is attenuated laser, when the SPAD detects photons, a pulse signal is generated, and the pulse signal is used as a stop signal of the TDC. A signal source Ref built in the RNGM generates a reference signal with a period T, and inputs the TDC as a start signal of the TDC. The FPGA takes the output of the TDC as input, and generates an original random bit string which is approximately uniformly distributed. For the original random bits, the Toplitz matrix is used to extract the final random bit string, which is also done in FPGA. Therefore, the output of the entire RNGM is the final ideal random bit string.
The invention provides a quantum key distribution system based on quantum random numbers, which uses an optical switch to control an optical path based on an F-M system, and uses a random number generation module to generate a random bit string, wherein the final overall structure is shown in FIG. 6.
The quantum key distribution system based on quantum random number of the invention includes: the device comprises a sender main control module, a receiver main control module, a laser diode LD, an optical attenuator ATT, a random number generation module RNGM, a rotating mirror FM1, a rotating mirror FM2, a rotating mirror FM3, a rotating mirror FM4, a coupler C1, a coupler C2, a phase modulator PMa, a phase modulator PMb and a single photon avalanche diode SPAD.
Specifically, an optical switch S1 is provided at the output end of the laser diode LD, a port P1 is provided at the input end of the optical attenuator ATT, a port P2 is provided at the input end of the coupler C1, an optical switch S2 is provided at the output end of the optical attenuator ATT, a port P3 is provided at the input end of the coupler C2, and a port P4 is provided at the input end of the RNGM.
In particular, the method comprises the following steps of,
the sender main control module is used for controlling the on-off of the optical switch and the port and controlling the modulation of the quantum state of the laser light source;
the receiving party main control module is used for controlling the measurement of the received quantum state;
the laser diode LD is used for outputting continuous laser;
the optical attenuator ATT is used for reducing the laser intensity to a level that the average number of photons arriving in each time interval is less than 1;
the random number generation module RNGM is used for generating a random bit string;
the rotating mirror FM1 is used for reflecting the pulse transmitted along the short arm and separated by the coupler C1 back to the coupler C1;
the phase modulator PMa is used for modulating the pulse transmitted along the long arm and branched by the coupler C1;
the rotating mirror FM2 is used for reflecting the pulse modulated by the phase modulator PMa back to the coupler C1;
the coupler C2 is used for dividing the pulse sent by the optical attenuator ATT into two beams;
the rotating mirror FM3 is used for reflecting the pulse transmitted along the short arm and separated by the coupler C2 back to the coupler C2;
the phase modulator PMb is used for modulating the pulse transmitted along the short arm and branched by the coupler C2;
the rotating mirror FM4 is used for reflecting the pulse modulated by the phase modulator PMb back to the coupler C2;
the single photon avalanche diode SPAD is used for detecting pulses emitted by the coupler C2, the pulses reflected by the rotating mirror FM3 and the pulses reflected by the modulator PMb reach the coupler C2 at the same time and interfere with each other, and the single photon avalanche diode SPAD detects the pulses emitted by the coupler C2.
Compared with an F-M system, the system redesigns an Alice area. Firstly, an optical switch S1 is added at the output of the laser diode LD, and when it is communicated with the port P1, the laser pulse will be transmitted to the optical attenuator ATT; when it is in communication with port P2, the laser pulse will pass to coupler C1. Secondly, an optical switch S2 is added at the output of the ATT, when the optical switch S2 is communicated with a port P3, laser pulses are sent to Bob through a quantum channel; when it is in communication with port P4, the laser pulse will enter the random number generating module RNGM.
Based on the system, the invention provides a quantum key distribution method based on quantum random numbers, taking BB84 protocol as an example, the quantum key distribution process can be divided into two stages.
The first stage is a random number generation stage. In this stage, the master control module at the sender controls the optical switch S1 to communicate with the port P1, and S2 to communicate with the port P4. Laser pulses emitted by the LD enter the RNGM after passing through the ATT, and finally the RNGM outputs a random bit string with the length of n.
The second phase is the key distribution phase. In this stage, the master control module at the sender controls the optical switch S1 to communicate with the port P2, and S2 to communicate with the port P3. The system works in the same way as a traditional F-M system, and Alice and Bob can complete the subsequent steps of the BB84 protocol by controlling the phase modulators PMa and PMb. The method comprises the following specific steps:
the sender main control module calls the random number generated by the random number generation module RNGM to modulate the quantum state of the laser light source;
the modulated quantum state enters a coupler C1 and is divided into two pulses which are transmitted along the short arm and two pulses which are transmitted along the long arm;
the pulse transmitted along the short arm is reflected to the coupler C1 through the rotating mirror FM1, and the pulse transmitted along the long arm is modulated by the phase modulator PMa and then reflected to the coupler C1 through the rotating mirror FM 2;
the two pulses entering the coupler C1 are coupled in a quantum channel and sent to the coupler C2, and are divided into two pulses which are transmitted along the short arm and two pulses which are transmitted along the long arm;
the pulse modulated by the phase modulator PMa is transmitted along the short arm and reflected to the coupler C2 through the rotating mirror FM3, and the pulse not modulated is transmitted along the long arm and reflected to the coupler C2 through the rotating mirror FM4 after being modulated by the phase modulator PMb;
the two pulses entering coupler C2 are coupled in a quantum channel and detected by a single photon avalanche diode;
and measuring the detected quantum state, and comparing the basis vectors of the measurement result through a classical channel to obtain the screened key.
The quantum key distribution system can realize all functions of the F-M system and has all advantages of the F-M system, so that the quantum key distribution system can be used for long-distance optical quantum communication and has strong anti-interference capability. Unlike the F-M system, the system proposed by the present invention also integrates the QRNG function. In the current mainstream solution, the two phases of tasks are generally performed by two independent hardware systems. The random number generation phase is performed by an independent RNG, and the key distribution phase is typically performed by the F-M system. The system of the present invention is compared to two combination schemes, depending on the type of RNG.
(1) Combination scheme of independent classical RNG (random number generator) and F-M system
The classical RNG adopts a deterministic algorithm to generate random numbers, and the possibility of being predicted exists; while QRNG takes advantage of physical randomness and is therefore unpredictable. The system of the invention can avoid the leakage of random numbers and improve the safety.
(2) Independent QRNG and F-M system combination scheme
There are duplicate physical devices of QRNG and F-M systems based on photon arrival times. The system of the invention multiplexes a laser diode and an optical attenuator, and adopts a modularized method to package the rest devices in the QRNG as RNGM to be accessed into the F-M system. Its advantage is low hardware cost while not reducing the security of random number.
The invention improves the F-M system by combining with a QRNG implementation scheme based on the arrival time of photons. And the circuit is modified to a certain extent by using an optical switch, and the RNGM is accessed, so that the upgrading of the F-M system is realized. The improved quantum key distribution system not only has the advantages of an F-M system, but also can effectively avoid the safety problem caused by random number leakage, and further guarantee is provided for the safe operation of the smart grid.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (11)
1. A quantum key distribution system based on quantum random numbers, comprising: an F-M system and a random number generation module;
the random number generation module is used for generating a random bit string;
the F-M system is used for carrying out quantum state modulation on a laser light source by adopting the random bit string to generate and distribute a quantum key;
the F-M system comprises a laser diode, an optical attenuator, a coupler C1 and a coupler C2;
the output end of the laser diode is provided with an optical switch S1, the input end of the optical attenuator is provided with a port P1, the input end of a coupler C1 is provided with a port P2, the output end of the optical attenuator is provided with an optical switch S2, and the input end of a coupler C2 is provided with a port P3;
the input end of the random number generation module is provided with a port P4;
in the random number generation stage of the quantum key distribution system, the optical switch S1 is communicated with the port P1, and the optical switch S2 is communicated with the port P4;
in the quantum key distribution system, in the key distribution stage, the optical switch S1 is communicated with the port P2, and the optical switch S2 is communicated with the port P3.
2. The quantum key distribution system based on quantum random number of claim 1, wherein the F-M system further comprises a sender master module, a receiver master module, a rotating mirror FM1, a rotating mirror FM2, a rotating mirror FM3, a rotating mirror FM4, a phase modulator PMa, a phase modulator PMb and a single photon avalanche diode;
the laser diode is used for outputting continuous laser;
the optical attenuator is used for reducing the intensity of the received light beam to a level that the average number of photons arriving in each time interval T is less than 1;
the rotating mirror FM1 is used for reflecting the pulse transmitted along the short arm and separated by the coupler C1 back to the coupler C1;
the phase modulator PMa is used for modulating the pulse transmitted along the long arm and branched by the coupler C1;
the rotating mirror FM2 is used for reflecting the pulse modulated by the phase modulator PMa back to the coupler C1;
the coupler C1 is used for dividing the laser emitted by the laser diode into two beams and coupling the two reflected beams;
the coupler C2 is used for dividing the pulse sent by the optical attenuator into two beams; coupling the two reflected laser beams;
the rotating mirror FM3 is used for reflecting the pulse transmitted along the short arm and separated by the coupler C2 back to the coupler C2;
the phase modulator PMb is used for modulating the pulse transmitted along the long arm and branched by the coupler C2;
the rotating mirror FM4 is used for reflecting the pulse modulated by the phase modulator PMb back to the coupler C2;
the single photon avalanche diode is used for detecting the pulse emitted by the coupler C2;
the sender main control module is used for controlling the on-off of the optical switch and the port and controlling the modulation of the quantum state of the laser light source;
and the receiver main control module is used for controlling the measurement of the received laser quantum state.
3. The quantum key distribution system based on quantum random numbers of claim 2, wherein the sender master module is specifically configured to,
in the random number generation phase, the optical switch S1 is controlled to be communicated with the port P1, and the optical switch S2 is controlled to be communicated with the port P4;
during the key distribution phase, optical switch S1 is controlled to communicate with port P2, and optical switch S2 communicates with port P3.
4. The quantum key distribution system based on quantum random numbers of claim 2, wherein the sender master module is specifically configured to,
and calling the random bit string generated by the random number generation module to modulate the quantum state of the laser light source.
5. A quantum key distribution system based on quantum random numbers according to claim 2, wherein the optical attenuator is specifically configured to,
when the optical switch S1 is communicated with the port P1, the intensity of the laser light emitted by the laser diode is reduced to a level that the average photon number arriving in each time interval is less than 1;
when the optical switch S1 is in communication with port P2, the pulses coupled by coupler C1 are dropped to a level where the average number of photons arriving in each time interval is less than 1.
6. The quantum key distribution system based on quantum random numbers of claim 2, wherein the receiver master control module is specifically configured to,
measuring the quantum state detected by the single photon avalanche diode;
and comparing the basis vectors of the measurement results through a classical channel to obtain the screened key.
7. A quantum key distribution system based on quantum random numbers according to claim 1, wherein the optical switches S1 and S2 are mechanical optical switches.
8. The quantum key distribution system based on quantum random numbers of claim 1, wherein the random number generation module comprises: a built-in signal source Ref, a single photon avalanche diode, a digital time converter and an FPGA;
the single photon avalanche diode is used for detecting photons emitted by the optical attenuator and generating a pulse signal;
the built-in signal source Ref is used for generating a reference signal with a period T;
the digital time converter is used for receiving a pulse signal generated by the single photon avalanche diode as a stop signal and receiving a reference signal generated by a built-in signal source Ref as a start signal;
the FPGA is used for generating original random bits according to the output of the digital-to-time converter and extracting a final random bit string by adopting a Toplitz matrix.
9. A quantum key distribution method based on quantum random numbers is characterized by comprising the following steps:
controlling the optical switch S1 to communicate with the port P1, S2 to communicate with the port P4 in the quantum key distribution system of any one of claims 1 to 8;
controlling the laser diode to emit continuous laser and entering the optical attenuator;
reducing the intensity of the received laser beam to the level that the average photon number arriving in each time interval T is less than 1, and transmitting the laser beam to a random number generation module to generate a random bit string;
calling a random bit string generated by a random number generation module to carry out quantum state modulation on a laser light source emitted by a laser diode;
controlling an optical switch S1 to be communicated with a port P2 and S2 to be communicated with a port P3 in the quantum key distribution system;
the modulated quantum state enters a coupler C1 and is divided into two pulses which are transmitted along the short arm and two pulses which are transmitted along the long arm;
the pulse transmitted along the short arm is reflected to the coupler C1 through the rotating mirror FM1, and the pulse transmitted along the long arm is modulated by the phase modulator PMa and then reflected to the coupler C1 through the rotating mirror FM 2;
the two pulses entering the coupler C1 are coupled in a quantum channel and sent to the coupler C2, and are divided into two pulses which are transmitted along the short arm and two pulses which are transmitted along the long arm;
the pulse modulated by the phase modulator PMa is transmitted along the short arm and reflected to the coupler C2 through the rotating mirror FM3, and the pulse not modulated is transmitted along the long arm and reflected to the coupler C2 through the rotating mirror FM4 after being modulated by the phase modulator PMb;
the two pulses entering coupler C2 are coupled in a quantum channel and detected by a single photon avalanche diode;
and measuring the detected quantum state and screening out the key.
10. The quantum key distribution method based on quantum random number of claim 9, wherein the random number generation module generates a random bit string, comprising:
the single photon avalanche diode detects photons emitted by the optical attenuator and generates a pulse signal, and a built-in signal source Ref generates a reference signal with a period T;
the digital time converter receives a pulse signal generated by the single photon avalanche diode as a stop signal, receives a reference signal generated by a built-in signal source Ref as a start signal, and generates and outputs the start signal;
the FPGA takes the output of the digital-to-time converter as input and generates an original random bit string.
11. The quantum key distribution method based on quantum random number as claimed in claim 10, further comprising,
the Toplitz matrix is used to extract the final random bit string from the original random bit string.
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