CN107135065B - Quantum key distribution method, transmitting device and receiving device - Google Patents

Abstract

Embodiments of the present invention relate to the field of quantum communication, and in particular, to a quantum key distribution method, a sending device, and a receiving device, which are used to more accurately recover the original key during the quantum key distribution process. In the embodiment of the present invention, the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal, so the time interval between the pulse of the quantum optical signal and the pulse of the adjacent reference optical signal When the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and estimates the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, the error will be reduced, and then According to the phase frequency information between the pulse of the quantum optical signal with reduced error and the local oscillator optical signal, the modulation of the local oscillator optical signal used for coherent coupling of the quantum optical signal will be more accurate, and then recovered from the quantum optical signal. The original key will be more accurate.

Description

A quantum key distribution method, sending device, and receiving device

technical field

Embodiments of the present invention relate to the field of quantum communication, and in particular, to a quantum key distribution method, a sending device, and a receiving device.

Background technique

With the rapid development of network technology, a large amount of sensitive information needs to be transmitted through the network, and people need to protect sensitive information from being lost or attacked. Encryption is one of the important means to ensure information security. The existing classical encryption system is based on computational complexity, which may be deciphered. In the classical cryptosystem, only one-time pad has unconditional security, and how to generate a large number of random number keys has always been a difficult problem. The emergence of Quantum Key Distribution (QKD) technology has solved this problem.

QKD specifically uses the quantum state as the information unit, and uses some principles of quantum mechanics to transmit and protect information. Usually, the two parties of the communication take the quantum state as the information carrier, and use the principles of quantum mechanics to transmit through the quantum channel to establish a confidential communication between the two parties. Shared key. Its security is guaranteed by the "Heisenberg uncertainty relation" and "single quantum non-replicability theorem" in quantum mechanics or the coherence and non-locality of entangled particles.

Fig. 1a exemplarily shows a schematic diagram of a system structure suitable for quantum key distribution. As shown in Figure 1a, it includes a sending device 101 and a receiving device 102. The sending device includes a main control unit 103, a quantum transmitter 104, a synchronous clock transmitter 105, a negotiation information transceiver 106, and a service information transmitter 107. In the receiving device It includes a main control unit 108 , a quantum receiver 109 , a synchronous clock receiver 110 , a negotiation information transceiver 111 , and a service information receiver 112 . The transmitting device sends the quantum optical signal carrying the original key to the quantum receiver of the receiving device through the quantum transmitter, so that the receiving device can recover the original quantum key from the quantum optical signal. The sending device sends a synchronous clock signal to a synchronous clock receiver of the receiving device through the synchronous clock transmitter, so that the receiving device realizes clock synchronization with the sending device. The sending device sends and receives negotiation information between the negotiation information transceiver and the negotiation information transceiver of the receiving device, so that the sending device and the receiving device determine the final quantum key from the original quantum key according to the negotiation information. The sending device sends the service information to the receiving device and the service information receiver through the service information transmitter.

The quantum key distribution process specifically refers to that the transmitting device carries the original key in the quantum optical signal, and sends the quantum optical signal to the receiving device. After the receiving device receives the quantum optical signal, it recovers from the quantum optical signal The original key is obtained, and the final key used is determined from the original key through negotiation between the sending device and the receiving device.

In the prior art, the transmitting device generates a local oscillator optical signal, and transmits the local oscillator optical signal and the quantum optical signal in the same optical fiber. The time when the optical signal and the quantum optical signal arrive at the input end of the 2:2 coupler, that is to say, the receiving device needs to strictly control the equal length of the path traversed by the local oscillator optical signal and the quantum optical signal. It is very difficult to use in engineering.

In conclusion, there is an urgent need for a quantum key distribution method, a transmitting device, and a receiving device, which can be used to recover the original key more simply in the quantum key distribution process.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a quantum key distribution method, a sending device, and a receiving device, which are used to more simply restore the original key during the quantum key distribution process.

An embodiment of the present invention provides a sending device for quantum key distribution, including:

The optical signal generating unit is used to perform spectral processing on the generated optical signal to obtain the first optical signal and the second optical signal; send the first optical signal to the first modulation unit, and send the second optical signal to the second modulation unit unit;

a first modulation unit, configured to perform chopping processing on the first optical signal to obtain a first optical pulse signal; attenuate and modulate the first optical pulse signal to obtain a reference optical signal, and send the reference optical signal to the coupling unit;

a second modulation unit, configured to perform chopping processing on the second optical signal to obtain a second optical pulse signal; attenuate and modulate the second optical pulse signal to obtain a quantum optical signal, and send the quantum optical signal to the coupling unit; the frequency of the pulses included in the first optical pulse signal is greater than the frequency of the pulses included in the second optical pulse signal;

The coupling unit is used to combine the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, and transmit the transmission optical signal to the receiving device.

Since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal; that is, since the frequency of the pulse included in the reference optical signal is larger, the pulse of the quantum optical signal is the same as the adjacent reference optical signal. The time interval between the pulses of the optical signal is small, and when the receiving device measures the phase frequency information between the pulses of the reference optical signal and the local oscillator optical signal, and then according to the difference between the pulses of the reference optical signal and the local oscillator optical signal. The phase frequency information will reduce the error when estimating the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then use the phase-frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error to be used for matching. The adjustment of the local oscillator optical signal coherently coupled by the quantum optical signal will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

Optionally, the coupling unit includes a polarization rotation unit connected to the first modulation unit, and a polarization coupling unit connected to the polarization rotation unit and the second modulation unit at the same time;

a polarization rotation unit, configured to rotate the polarization state of the received reference optical signal by a first angle, and send the reference optical signal whose polarization state is rotated by the first angle to the polarization coupling unit;

The polarization coupling unit is used to perform polarization coupling processing on the received quantum optical signal pulse and the reference optical signal whose polarization state is rotated by the first angle, so as to obtain one channel of polarization multiplexing and time division multiplexing of the reference optical signal and the quantum optical signal to be transmitted the transmission optical signal, and transmit the transmission optical signal to the receiving device;

or,

The coupling unit includes a polarization rotation unit connected with the second modulation unit, and a polarization coupling unit connected with the polarization rotation unit and the first modulation unit at the same time;

a polarization rotation unit, configured to rotate the polarization state of the received quantum optical signal by a second angle, and send the quantum optical signal whose polarization state is rotated by the second angle to the polarization coupling unit;

The polarization coupling unit is used to perform polarization coupling processing on the received reference optical signal pulse and the quantum optical signal whose polarization state is rotated by a second angle, so as to obtain one channel of polarization multiplexing and time division multiplexing of the reference optical signal and the quantum optical signal to be sent the transmission optical signal, and send the transmission optical signal to the receiving device.

In this way, polarization multiplexing and time-division multiplexing of the reference optical signal and the quantum optical signal are realized, which further improves the isolation between the quantum optical signal and the reference optical signal, and reduces the interference between the quantum optical signal and the reference optical signal. .

Optionally, the first modulation unit is further configured to modulate classical information on the first optical pulse signal, so that the reference optical signal includes classical information. In this way, the utilization rate of the reference optical signal can be improved, thereby improving the transmission efficiency of information in the quantum key distribution process.

An embodiment of the present invention provides a receiving apparatus for quantum key distribution, including:

The coherent coupling unit is used to perform spectral processing on the received transmission optical signal including the reference optical signal and the quantum optical signal, and perform coherent coupling on the transmission optical signal after the spectral processing according to the local oscillator optical signal, so as to obtain the reference optical signal including the reference optical signal. The first coherently coupled optical signal and the second coherently coupled optical signal including the quantum optical signal; the first coherently coupled optical signal is sent to the reference optical balance detection unit, and the second coherently coupled optical signal is sent to the quantum Optical balance detection unit; wherein, the pulse appearance frequency of the reference optical signal included in the optical signal after the first coherent coupling is the first frequency, and the pulse appearance frequency of the quantum optical signal included in the optical signal after the second coherent coupling is the second frequency , the first frequency is greater than the second frequency;

The local oscillator unit is used to generate the local oscillator optical signal and send the local oscillator optical signal to the coherent coupling unit;

The reference optical balance detection unit is used to perform photoelectric conversion on the first coherently coupled optical signal, perform differential processing and amplification, obtain the first electrical signal, and transmit the first electrical signal to the carrier recovery unit;

The quantum optical balance detection unit is used to perform photoelectric conversion on the second coherently coupled optical signal, perform differential processing and amplification, obtain the second electrical signal, and transmit the second electrical signal to the key recovery unit;

a carrier recovery unit, configured to determine the phase frequency information between the local oscillator optical signal and the reference optical signal from the first electrical signal;

The key recovery unit is used for recovering the original key from the second electrical signal according to the received phase frequency information.

Since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal; that is, since the frequency of the pulse included in the reference optical signal is larger, the pulse of the quantum optical signal is the same as the adjacent reference optical signal. The time interval between the pulses of the optical signal is small, and when the receiving device measures the phase frequency information between the pulses of the reference optical signal and the local oscillator optical signal, and then according to the difference between the pulses of the reference optical signal and the local oscillator optical signal. The phase frequency information will reduce the error when estimating the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then use the phase-frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error to be used for matching. The adjustment of the local oscillator optical signal coherently coupled by the quantum optical signal will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

Optionally, the bandwidth of the reference light balance detection unit is higher than the bandwidth of the quantum light balance detection unit; the gain of the reference light balance detection unit is lower than the gain of the quantum light balance detection unit. In this way, the gain of the reference light balance detection unit to the pulse of the reference light signal can be optimized, and the detection of the quantum light signal by the quantum light balance detection unit is not affected.

Optionally, polarization multiplexing of the reference optical signal and the quantum optical signal included in the transmission optical signal;

The coherent coupling unit includes a polarization beam splitting unit, a first sub-coherent coupling unit and a second sub-coherent coupling unit connected to the polarization beam splitting unit, the first sub-coherent coupling unit is connected to the reference light balance detection unit, and the second sub-coherent coupling unit is connected to the quantum Light balance detection unit;

The local oscillator unit is used to generate a local oscillator optical signal, and divide the local oscillator optical signal into a first sub-local oscillator optical signal and a second sub-local oscillator optical signal; send the first sub-local oscillator optical signal to the first sub-coherent optical signal a coupling unit; sending the second sub-local oscillator optical signal to the second sub-coherent coupling unit;

a polarization splitting unit, configured to divide the transmitted optical signal into a first split-processed optical signal including a reference optical signal and a second split-processed optical signal including a quantum optical signal through polarization split processing;

a first sub-coherent coupling unit, configured to use the first sub-local oscillator optical signal to perform coherent coupling on the first optical signal after splitting processing, and output the first optical signal after coherent coupling;

The second sub-coherent coupling unit is configured to use the second sub-local oscillator optical signal to perform coherent coupling on the second optical signal after splitting processing, and output the second optical signal after coherent coupling.

Optionally, the local oscillator unit includes a local oscillator optical splitting unit, a first local oscillator modulation unit and a second local oscillator modulation unit connected to the local oscillator optical splitting unit, and the first local oscillator modulation unit is connected to the first sub-coherent coupling unit; Two local oscillator modulation units are connected to the second sub-coherent coupling unit;

The local oscillator optical splitting unit is configured to divide the generated local oscillator optical signal into a third sub-local oscillator optical signal and a fourth sub-local oscillator optical signal, and send the third sub-local oscillator optical signal to the first local oscillator modulation unit, The fourth sub-local oscillator optical signal is sent to the second local oscillator modulation unit; the polarization state of the third sub-local oscillator optical signal is the same as that of the optical signal after the first optical splitting processing, and the fourth sub-local oscillator optical signal and the second optical splitting processing are in the same polarization state. The polarization state of the optical signal is consistent;

The first local oscillator modulation unit is used for chopping the third sub-local oscillator optical signal to obtain the first optical pulse local oscillator signal; and performing phase modulation on the first optical pulse local oscillator signal to obtain the first sub-local oscillator an optical signal; the frequency of the pulse included in the first optical pulse local oscillator signal is the first frequency;

The second local oscillator modulation unit is configured to perform chopping processing on the fourth sub-local oscillator optical signal to obtain the second optical pulse local oscillator signal; and perform phase modulation on the second optical pulse local oscillator signal according to the phase frequency information to obtain the first optical pulse local oscillator signal. Two sub-local oscillator optical signals; the frequency of the pulses included in the second optical pulse local oscillator signal is the second frequency.

Optionally, the first local oscillation modulation unit is further configured to:

delaying the first optical pulse local oscillator signal in the time domain, so that the pulse in the obtained first sub-local oscillator optical signal corresponds in the time domain with the pulse of the reference optical signal included in the optical signal after the first spectral processing; so that the first local oscillation modulation unit performs phase modulation on the first optical pulse local oscillation signal delayed in the time domain;

The second local oscillator modulation unit is also used for:

delaying the second optical pulse local oscillator signal in the time domain, so that the pulse in the second sub-local oscillator optical signal obtained corresponds in the time domain with the pulse of the quantum optical signal included in the optical signal after the second spectral processing; So that the second local oscillation modulation unit performs phase modulation on the second optical pulse local oscillation signal delayed in the time domain.

Optionally, the reference optical balance detection unit is also used to perform in-phase quadrature IQ detection on the first electrical signal, and transmit the first electrical signal that has undergone IQ detection to the carrier recovery unit;

The carrier recovery unit is further configured to demodulate the classical information modulated on the reference optical signal from the first electrical signal subjected to IQ detection. In this way, the utilization rate of the reference optical signal can be improved, thereby improving the transmission efficiency of information in the quantum key distribution process.

An embodiment of the present invention provides a quantum key distribution method, including:

The transmitting device performs spectral processing on the generated optical signal to obtain the first optical signal and the second optical signal;

The sending device performs chopping processing on the first optical signal to obtain a first optical pulse signal; and attenuates and modulates the first optical pulse signal to obtain a reference optical signal;

The sending device performs chopping processing on the second optical signal to obtain a second optical pulse signal; attenuates and modulates the second optical pulse signal to obtain a quantum optical signal; the frequency of the pulses included in the first optical pulse signal is greater than that of the second optical pulse signal the frequency of the pulses included in the optical pulse signal;

The sending device performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, and transmits the transmission optical signal to the receiving device.

Since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal; that is, since the frequency of the pulse included in the reference optical signal is larger, the pulse of the quantum optical signal is the same as the adjacent reference optical signal. The time interval between the pulses of the optical signal is small, and when the receiving device measures the phase frequency information between the pulses of the reference optical signal and the local oscillator optical signal, and then according to the difference between the pulses of the reference optical signal and the local oscillator optical signal. The phase frequency information will reduce the error when estimating the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then use the phase-frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error to be used for matching. The adjustment of the local oscillator optical signal coherently coupled by the quantum optical signal will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

Optionally, the sending device performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, including:

Rotate the polarization state of the received reference optical signal by a first angle; perform polarization coupling processing on the received quantum optical signal pulse and the reference optical signal whose polarization state is rotated by the first angle, to obtain the polarization complex of the reference optical signal and the quantum optical signal. A transmission optical signal to be transmitted is used and time-division multiplexed;

or,

Rotate the polarization state of the received quantum optical signal by a second angle; perform polarization coupling processing on the received reference optical signal pulse and the quantum optical signal whose polarization state is rotated by the second angle to obtain the polarization complex of the reference optical signal and the quantum optical signal. A transmission optical signal to be sent is used and time-division multiplexed.

Optionally, before the sending device performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, the sending device is further used for:

The classical information is modulated on the first optical pulse signal, so that the classical information is included in the reference optical signal.

An embodiment of the present invention provides a quantum key distribution method, including:

The receiving device generates a local oscillator optical signal, performs spectroscopic processing on the received transmission optical signal including the reference optical signal and the quantum optical signal, and performs coherent coupling on the transmitted optical signal after the spectroscopic processing according to the local oscillator optical signal, to obtain the reference optical signal including the reference optical signal and the quantum optical signal. The first coherently coupled optical signal of the optical signal and the second coherently coupled optical signal including the quantum optical signal; wherein, the pulse appearance frequency of the reference optical signal included in the first coherently coupled optical signal is the first frequency, and the second The pulse appearance frequency of the quantum optical signal included in the optical signal after the coherent coupling is the second frequency, and the first frequency is greater than the second frequency;

The receiving device performs photoelectric conversion on the first coherently coupled optical signal, performs differential processing and amplification to obtain a first electrical signal; performs photoelectric conversion on the second coherently coupled optical signal, performs differential processing and amplification to obtain a second electrical signal;

The receiving device determines the phase frequency information between the local oscillator optical signal and the reference optical signal from the first electrical signal; and recovers the original key from the second electrical signal according to the phase frequency information.

Since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal; that is, since the frequency of the pulse included in the reference optical signal is larger, the pulse of the quantum optical signal is the same as the adjacent reference optical signal. The time interval between the pulses of the optical signal is small, and when the receiving device measures the phase frequency information between the pulses of the reference optical signal and the local oscillator optical signal, and then according to the difference between the pulses of the reference optical signal and the local oscillator optical signal. The phase frequency information will reduce the error when estimating the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then use the phase-frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error to be used for matching. The adjustment of the local oscillator optical signal coherently coupled by the quantum optical signal will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

Optionally, polarization multiplexing of the reference optical signal and the quantum optical signal included in the transmission optical signal;

The receiving device generates a local oscillator optical signal, performs spectroscopic processing on the received transmission optical signal including the reference optical signal and the quantum optical signal, and performs coherent coupling on the transmitted optical signal after the spectroscopic processing according to the local oscillator optical signal, to obtain the reference optical signal including the reference optical signal and the quantum optical signal. The first coherently coupled optical signal of the optical signal and the second coherently coupled optical signal including the quantum optical signal include:

The receiving device generates a local oscillator optical signal, and divides the local oscillator optical signal into a first sub-local oscillator optical signal and a second sub-local oscillator optical signal;

The receiving device divides the transmission optical signal into a first spectrally processed optical signal including a reference optical signal and a second spectrally processed optical signal including a quantum optical signal by polarization splitting processing;

The receiving device uses the first sub-local oscillator optical signal to coherently couple the optical signal after the first splitting process, and outputs the first coherently coupled optical signal; and uses the second sub-local oscillator optical signal to coherently couple the second splitting-processed optical signal , and output the second coherently coupled optical signal.

Optionally, the receiving device generates a local oscillator optical signal, and divides the local oscillator optical signal into a first sub-local oscillator optical signal and a second sub-local oscillator optical signal, including;

The receiving device divides the generated local oscillator optical signal into a third sub-local oscillator optical signal and a fourth sub-local oscillator optical signal; the third sub-local oscillator optical signal and the polarization state of the optical signal after the first splitting process are consistent, and the fourth sub-local oscillator optical signal has the same polarization state. The polarization states of the local oscillator optical signal and the optical signal after the second splitting process are consistent;

The receiving device performs chopping processing on the third sub-local oscillator optical signal to obtain a first optical pulse local oscillator signal; and performs phase modulation on the first optical pulse local oscillator signal to obtain a first sub-local oscillator optical signal; the first optical pulse The frequency of the pulse included in the local oscillator signal is the first frequency;

The receiving device performs chopping processing on the fourth sub-local oscillator optical signal to obtain a second optical pulse local oscillator signal; and performs phase modulation on the second optical pulse local oscillator signal according to the phase frequency information to obtain a second sub-local oscillator optical signal; The frequency of the pulse included in the second optical pulse local oscillator signal is the second frequency.

Optionally, the receiving device performs chopping processing on the third sub-local oscillator optical signal to obtain the first optical pulse local oscillator signal, and before performing phase modulation on the first optical pulse local oscillator signal, further comprising:

delaying the first optical pulse local oscillator signal in the time domain, so that the pulse in the obtained first sub-local oscillator optical signal corresponds in the time domain with the pulse of the reference optical signal included in the optical signal after the first spectral processing;

The receiving device performs chopping processing on the fourth sub-local oscillator optical signal to obtain the second optical pulse local oscillator signal and before performing phase modulation on the second optical pulse local oscillator signal, further comprising:

The second optical pulse local oscillator signal is delayed in the time domain, so that the pulse in the second sub-local oscillator optical signal obtained corresponds in the time domain with the pulse of the quantum optical signal included in the optical signal after the second spectral processing.

Optionally, after the receiving device performs photoelectric conversion on the first coherently coupled optical signal and performs differential processing and amplification to obtain the first electrical signal, the method further includes:

In-phase quadrature IQ detection is performed on the first electrical signal, and classical information modulated on the reference optical signal is demodulated from the IQ-detected first electrical signal.

In the embodiment of the present invention, the generated optical signal is subjected to spectroscopic processing, and the obtained first optical signal and the second optical signal are respectively subjected to chopping processing to obtain the first optical pulse signal and the second optical pulse signal, and then the first optical pulse signal and the second optical pulse signal are obtained. The pulse signal and the second optical pulse signal are respectively attenuated and modulated to obtain a reference optical signal and a quantum optical signal; the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal; The signal and the quantum optical signal are combined and processed to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, and the transmission optical signal is transmitted to the receiving device. It can be seen that, on the one hand, there is no need to strictly control the length difference between the two optical fibers of the transmitting device and the receiving device, which reduces the technical difficulty and achieves a simpler purpose of recovering the original key in the quantum key distribution process.

Further, in the embodiment of the present invention, since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal; that is, since the frequency of the pulse included in the reference optical signal is relatively large, the quantum light The time interval between the pulse of the signal and the pulse of the adjacent reference optical signal is small, and when the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and then according to the pulse of the reference optical signal The error will be reduced when estimating the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then according to the reduced error between the pulse of the quantum optical signal and the local oscillator optical signal The adjustment of the local oscillator optical signal used to coherently couple the quantum optical signal will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following will briefly introduce the accompanying drawings used in the description of the embodiments.

1a is a schematic diagram of a system structure suitable for quantum key distribution provided in the prior art;

FIG. 1b is a schematic structural diagram of a system to which an embodiment of the present invention is applicable;

FIG. 1c is a schematic structural diagram of a system to which an embodiment of the present invention is applicable;

2a is a schematic structural diagram of a transmission device for quantum key distribution provided by an embodiment of the present invention;

FIG. 2b is a schematic structural diagram of a transmission optical signal according to an embodiment of the present invention;

2c is a schematic structural diagram of a transmission device for quantum key distribution provided by an embodiment of the present invention;

2d is a schematic structural diagram of a transmission device for quantum key distribution provided by an embodiment of the present invention;

2e is a schematic structural diagram of a transmission device for quantum key distribution provided by an embodiment of the present invention;

2f is a schematic structural diagram of a transmission device for quantum key distribution provided by an embodiment of the present invention;

3a is a schematic structural diagram of a receiving apparatus for quantum key distribution provided by an embodiment of the present invention;

3b is a schematic structural diagram of a receiving apparatus for quantum key distribution provided by an embodiment of the present invention;

3c is a schematic structural diagram of a receiving apparatus for quantum key distribution provided by an embodiment of the present invention;

4 is a schematic flowchart of a quantum key distribution method according to an embodiment of the present invention;

FIG. 5 is a schematic flowchart of another quantum key distribution method provided by an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In the embodiment of the present invention, the receiving device is included in the receiving device, and is used to recover the original key from the received quantum optical signal by a simpler and more accurate method on the receiving device side. The receiving device includes but is not limited to a base station, a station controller, an access point (Access Point, AP for short), or any other type of interface device that can work in a wireless environment.

Fig. 1b exemplarily shows a schematic diagram of a system structure to which an embodiment of the present invention is applicable, and Fig. 1c exemplarily shows a schematic diagram of another system structure to which an embodiment of the present invention is applicable.

As shown in FIG. 1b , in the system architecture to which the embodiment of the present invention is applicable, the node A only includes the sending device 1101 , and the node B only includes the receiving device 1102 . This system architecture is called a one-way system architecture. The sending device 1101 at node A carries the original key in the quantum optical signal, and sends it to the receiving device 1102. The receiving device 1102 recovers the original key from the quantum optical signal, and then the sending device 1101 and the receiving device 1102 recover the original key from the original key. The final quantum key is determined through negotiation in the key. Further, the sending device 1101 at the node A receives the input service information, uses the final quantum key to encrypt the service information, obtains an encrypted signal, and sends the encrypted signal to the receiving device 1102 . After receiving the encrypted signal, the receiving device 1102 uses the same final quantum key to perform a decryption process, decrypts and outputs the business information, and sends the information to the sending device 1101 through a classical channel.

In specific implementation, services are usually bidirectional, such as voice, video calls and other services. In the two-way business, each node needs encryption and decryption processing, and accordingly each node needs a set of QKD system. As shown in FIG. 1 c , the node A in the system architecture to which the embodiment of the present invention is applicable includes a sending device 1201 and a receiving device 1203 . The Node B includes a receiving device 1202 and a sending device 1204 . The transmitter 1201 and the receiver 1202 are a pair, and the transmitter 1204 and the receiver 1203 are a pair. This system architecture is called a bidirectional system architecture. A variety of information transmission methods can be implemented under the system architecture, and the pair of the sending device 1201 and the receiving device 1202 is taken as an example to introduce, for example:

The sending device 1201 at node A carries the original key in the quantum optical signal, and sends it to the receiving device 1202. The receiving device 1202 recovers the original key from the quantum optical signal, and then the sending device 1201 and the receiving device 1202 recover the original key from the original key. The final quantum key is determined through negotiation in the key.

The sending device 1201 at the node A encrypts the received service information using the final quantum key, and then sends the encrypted service information to the receiving device 1202 at the node B. The receiving device 1202 decrypts using the same final quantum key and outputs the service information. The receiving device 1202 sends information to the transmitting device 1201 through the classic channel. Alternatively, the receiving device 1202 feeds back information to the sending device 1201 through the sending device 1204 and the receiving device 1203 .

The embodiments of the present invention are applicable to the QKD technology. QKD technology includes Discrete Variable-Quantum Key Distribution (DV-QKD for short) and Continuous Variable-Quantum Key Distribution (CV-QKD for short). CV-QKD is more widely used in engineering because it does not need a single-photon detector working at low temperature, so the embodiments of the present invention are preferably applicable to CV-QKD technology. In the embodiments of the present invention, a self-referential continuous variable quantum key distribution system is used as an example for introduction.

The coherent coupling, photoelectric conversion and amplification mentioned in the embodiments of the present invention are all technical terms of coherent detection. In the embodiment of the present invention, the working principle of coherent detection is as follows: the sending device modulates the signal on the optical carrier by using an external modulation method for transmission. When the transmission optical signal of the transmitting device is transmitted to the receiving device, the receiving device coherently couples the received transmission optical signal with a local oscillator optical signal, and then performs detection by a balanced detector, which can also be described as detection using a balanced receiver. . Coherent optical communication can be divided into heterodyne detection and homodyne detection according to the frequency of the local oscillator optical signal and the frequency of the transmitted optical signal being unequal or equal.

Based on the above-mentioned system architecture and the problems in the quantum key distribution technology in the prior art, a self-referential continuous variable quantum key distribution technology has been developed. In this technology, the receiving device generates a local oscillator optical signal and transmits the The local oscillator optical signal and the quantum optical signal sent by the transmitting device are used for balanced detection. In order to accurately recover the original key, the transmitting device needs to send an additional reference optical signal to estimate the phase and frequency information of the quantum optical signal. There is an error in the estimation, which will affect the recovery of the final key.

Specifically, the solution is:

The transmitting device sends a transmission optical signal to the receiving device, and the transmission optical signal includes a time-division multiplexed reference optical signal and a quantum optical signal. After the receiving device receives the transmission optical signal, the receiving device locally generates a local oscillator optical signal, and uses the local oscillator optical signal to perform coherent detection on the received transmission optical signal. This process only uses a balanced receiver. In order to ensure stable interference between the local oscillator optical signal generated by the receiving device and the quantum optical signal that transmits the optical signal, it is necessary to introduce a strong optical signal between the two adjacent quantum optical signals included in the transmitted optical signal. reference optical signal. The receiving device determines the phase information between the reference optical signal and the local oscillator optical signal from the reference optical signal between the quantum optical signals, so that the receiving device realizes the random selection of the measurement base according to the phase information, and further determines the phase information between the reference optical signal and the local oscillator optical signal according to the phase information. to recover the original key information.

In the above scheme, the basic principle for the receiving device to determine the phase frequency information between the local oscillator optical signal and the reference optical signal is as follows: the pulse of the reference optical signal and the pulse of the adjacent quantum optical signal are very close in the time domain, and the reference optical signal Both the pulse of the reference optical signal and the pulse of the quantum optical signal pass through the same channel transmission, so it can be approximately considered that the pulse of the reference optical signal is changed during the transmission process due to the phase frequency information and the pulse of the adjacent quantum optical signal due to the occurrence of The phase frequency information generated by the change is consistent, or it is considered that the average value of the phase frequency information generated by the change of the pulses of the two reference optical signals before and after the pulse of a certain quantum optical signal is the same as the pulse of the quantum optical signal due to the change in the transmission process. The phase frequency information produced by the change is consistent. Therefore, the receiving device can estimate the phase frequency information between the quantum optical signal and the local oscillator optical signal according to the phase frequency information between the detected local oscillator optical signal and the reference optical signal, and then according to the quantum optical signal and the local oscillator optical signal The phase frequency information between the two adjusts the phase of the local oscillator optical signal used for coherent coupling of the quantum optical signal, and then uses the adjusted local oscillator optical signal to coherently couple the quantum optical signal, and from the coherently coupled quantum optical signal. The original key information is recovered from the optical signal.

The applicant found that, in this solution, on the one hand, in order to recover a high-gain signal from the quantum optical signal transmitting the optical signal, and then recover a more accurate original key, the balance used for the detection of the quantum optical signal is The receiver works at a lower bandwidth. Since the balanced receiver also needs to detect the reference optical signal, at this time, in order to recover the high-gain signal from the quantum optical signal, it is necessary to detect the optical signal in the transmitted optical signal. The frequency of occurrence of the included pulses for transmitting optical signals is limited, that is, the frequency of occurrences of pulses for transmitting optical signals will not be increased, for example, it can usually be in the order of 10 MHz.

On the other hand, since the local oscillator optical signal generated by the receiving device and the transmission optical signal are not generated by the same laser after all, there will still be a frequency difference between the two, which will affect the reference of the receiving device according to the transmission optical signal. The phase and frequency information of the quantum optical signal of the transmitted optical signal and the local oscillator optical signal estimated by the balance detection result of the optical signal and the local oscillator optical signal are affected, thereby obtaining inaccurate phase frequency information. In order to reduce the influence of the frequency difference on the phase frequency information to a negligible level, it is necessary to ensure that the occurrence frequency of the pulses of the transmission optical signal included in the transmission optical signal is greater than a certain threshold, for example, greater than 100 MHz.

It can be seen that in the above solution, in order to recover a high-gain signal from the quantum optical signal transmitting the optical signal, and then recover a more accurate original key, it is necessary to limit the frequency of occurrence of the pulse of the transmitted optical signal; The influence of the frequency difference on the phase frequency information is reduced to a negligible level, and it is necessary to ensure that the frequency of occurrence of the transmitted optical signal is greater than a certain threshold. Such a contradiction makes the working performance of the balanced receiver for detecting the reference optical signal and the quantum optical signal not optimal, and the accuracy of the detected result also decreases.

In view of the above problems, the embodiments of the present invention provide a quantum key distribution method, a sending device, and a receiving device. On the one hand, the solution does not require strict equal-length control on the length difference between the two optical fibers of the sending device and the receiving device, which reduces the technical Difficulty, to achieve a simpler purpose of recovering the original key during the quantum key distribution process. Further, in the embodiment of the present invention, since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal; that is, since the frequency of the pulse included in the reference optical signal is relatively large, the quantum light The time interval between the pulse of the signal and the pulse of the adjacent reference optical signal is small, and when the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and then according to the pulse of the reference optical signal The error will be reduced when estimating the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then according to the reduced error between the pulse of the quantum optical signal and the local oscillator optical signal The adjustment of the local oscillator optical signal used to coherently couple the quantum optical signal will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

Optionally, the phase frequency information in this embodiment of the present invention may include information such as a phase difference and a frequency difference between the local oscillator optical signal and the reference optical signal.

Fig. 2a exemplarily shows a schematic structural diagram of a sending apparatus for quantum key distribution provided by an embodiment of the present invention.

Based on the above system architecture and related discussions, as shown in FIG. 2a , a transmission device for quantum key distribution provided by an embodiment of the present invention includes an optical signal generation unit 2101 , a first modulation unit connected to the optical signal generation unit 2101 2102 and the second modulation unit 2103, and the coupling unit 2104 connected to the first modulation unit 2102 and the second modulation unit 2103 at the same time, the coupling unit 2104 finally outputs the transmission optical signal to the receiving device:

The optical signal generating unit 2101 is used to perform spectral processing on the generated continuous optical signal to obtain a first optical signal and a second optical signal; send the first optical signal to the first modulation unit 2102, and send the second optical signal to the second modulation unit 2103;

The first modulation unit 2102 is configured to perform chopping processing on the first optical signal to obtain a first optical pulse signal; attenuate and modulate the first optical pulse signal to obtain a reference optical signal, and send the reference optical signal to the coupling unit 2104;

The second modulation unit 2103 is configured to perform chopping processing on the second optical signal to obtain a second optical pulse signal; attenuate and modulate the second optical pulse signal to obtain a quantum optical signal, and send the quantum optical signal to the coupling unit 2104: The frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal;

The coupling unit 2104 is used to combine the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, and transmit the transmission optical signal to the receiving device.

Since the frequency of pulses included in the first optical pulse signal is greater than the frequency of pulses included in the second optical pulse signal, the frequency of occurrence of pulses of the reference optical signal in the transmission optical signal is greater than that of the quantum optical signal.

FIG. 2b exemplarily shows a schematic structural diagram of an optical signal transmission provided by an embodiment of the present invention. As shown in FIG. 2b, the abscissa is the time axis 2501, and the ordinate is the light intensity 2502 in the X polarization state and the light intensity 2505 in the Y polarization state, respectively. The reference optical signal 2504 is sent on the Y polarization state, and the quantum optical signal 2503 is sent on the Y polarization state. The frequency of the pulses of the reference optical signal 2504 is greater than the frequency of the pulses of the quantum optical signal 2503. Since the frequency is the inverse of the period, the period 2507 of the reference optical signal is smaller than the period 2506 of the quantum optical signal. In Fig. 2a, the quantum optical signal and the reference optical signal included in the transmission optical signal are polarization-multiplexed and time-division multiplexed.

The coupling unit 2104 performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted that includes the polarization multiplexing and time division multiplexing of the reference optical signal and the quantum optical signal, and transmits the transmission optical signal to the receiving device . The frequency of occurrence of pulses of the reference optical signal in the transmitted optical signal is greater than the frequency of occurrence of pulses of the quantum optical signal.

Optionally, when the reference optical signal and the quantum optical signal included in the transmission optical signal are polarization multiplexed and time-division multiplexed, the coupling unit 2104 may include various structural forms, and the following two optional implementations are provided in this embodiment of the present invention. Way. In different embodiments, the specific structural form of the coupling unit 2104 is described as follows.

FIG. 2c exemplarily shows a schematic structural diagram of a transmitting apparatus for quantum key distribution provided by an embodiment of the present invention. As shown in FIG. 2c, the coupling unit 2104 includes a polarization rotation unit connected to the first modulation unit 2102 2202, and a polarization coupling unit 2201 connected to the polarization rotation unit 2202 and the second modulation unit 2103 at the same time. Optionally, an optional structural form of the polarization rotation unit 2202 is: the polarization rotation unit 2202 includes a polarization beam splitter 2203 connected to the first modulation unit 2102, and the polarization beam splitter 2203 is connected to the Faraday mirror 2204 and the polarization beam splitter 2203. Coupling unit 2201. Optionally, the polarization coupling unit may be a polarization beam combiner.

As shown in FIG. 2c, the coupling unit 2104 includes a polarization rotation unit 2202 connected to the first modulation unit 2102, and a polarization coupling unit 2201 connected to the polarization rotation unit 2202 and the second modulation unit 2103 at the same time; the polarization rotation unit 2202 is used for Rotate the polarization state of the received reference optical signal by a first angle, and send the reference optical signal whose polarization state is rotated by the first angle to the polarization coupling unit 2201; the polarization coupling unit 2201 is used for the received quantum optical signal pulse, and performing polarization coupling processing on the reference optical signal whose polarization state is rotated by the first angle to obtain a transmission optical signal to be transmitted which is polarization multiplexed and time-division multiplexed of the reference optical signal and the quantum optical signal, and transmits the transmission optical signal to the receiving device.

FIG. 2d exemplarily shows a schematic structural diagram of a transmitting apparatus for quantum key distribution provided by an embodiment of the present invention. As shown in FIG. 2d , the coupling unit 2104 includes a polarization rotation unit 2202 connected to the second modulation unit 2103 , and the polarization coupling unit 2201 connected to the polarization rotation unit 2202 and the first modulation unit 2102 at the same time. Optionally, an optional structural form of the polarization rotation unit 2202 is: the polarization rotation unit 2202 includes a polarization beam splitter 2203 connected to the second modulation unit 2103, and the polarization beam splitter 2203 is connected to the Faraday mirror 2204 and the polarization beam splitter 2203. Coupling unit 2201.

As shown in FIG. 2d, the polarization rotation unit 2202 is used to rotate the polarization state of the received quantum optical signal by a second angle, and send the quantum optical signal whose polarization state is rotated by the second angle to the polarization coupling unit 2201; the polarization coupling unit 2201 is used to perform polarization coupling processing on the received reference optical signal pulse and the quantum optical signal whose polarization state is rotated by a second angle, so as to obtain a transmission to be sent that is polarization multiplexing and time-division multiplexing of the reference optical signal and the quantum optical signal optical signal, and send the transmitted optical signal to the receiving device.

In order to introduce the embodiment of the present invention more clearly, FIG. 2e exemplarily shows a schematic structural diagram of a transmitting apparatus for quantum key distribution in an embodiment of the present invention. As shown in FIG. 2e, the optical signal generating unit 2101 includes a laser 2301, and a beam splitter 2302 connected to the laser 2301; the beam splitter 2302 is connected to the first pulse modulator 2303 of the first modulation unit 2102, and the beam splitter 2302 is also connected to the second pulse modulator 2307 of the second modulation unit 2103, The first pulse modulator 2303 is connected to the first amplitude modulator 2304, the first amplitude modulator 2304 is connected to the first phase modulator 2305, the first phase modulator 2305 is connected to the first adjustable attenuator 2306; the second pulse modulator 2307 is connected to The second amplitude modulator 2308, the second amplitude modulator 2308 is connected to the second phase modulator 2309, and the second phase modulator 2309 is connected to the second adjustable attenuator 2310; based on the structure of the coupling unit 2104 shown in FIG. 2c above form, in FIG. 2e, the first adjustable attenuator 2306 is connected to the polarization beam splitter 2203 in the polarization rotation unit 2202, and the polarization beam splitter 2203 is connected to the Faraday mirror 2204 and the polarization coupling unit 2201 at the same time; the second adjustable attenuator 2310 is connected to the polarization coupling unit 2201.

The working principle of the sending device will be introduced in more detail with reference to FIG. 2e.

As shown in Fig. 2e, the light source of the laser 2301 emits continuous light, such as continuous light of 1550 nm; the continuous light emitted by the laser 2301 enters the beam splitter 2302 and is subjected to spectral processing to obtain the first optical signal and the second optical signal, and the first optical signal and the second optical signal are obtained. The optical signal is sent to the first pulse modulator 2303 of the first modulation unit 2102 , and the second optical signal is sent to the second pulse modulator 2307 of the second modulation unit 2103 .

The first pulse modulator 2303 performs chopping processing on the received first optical signal to form a first optical pulse signal with pulses having a certain repetition frequency; and performs amplitude modulation on the first optical pulse signal through the first amplitude modulator 2304 , the first optical pulse signal after amplitude modulation is phase-modulated by the first phase modulator 2305, and the first optical pulse signal subjected to amplitude and phase modulation is attenuated by the first adjustable attenuator 2306 to obtain the reference The optical signal, the reference optical signal is sent to the coupling unit 2104. Optionally, after the first pulse modulator 2303 generates the first optical pulse signal, the first optical pulse signal can also be attenuated by the first adjustable attenuator 2306, and then the amplitude and phase are modulated. Get the quantum light signal.

The second pulse modulator 2307 performs chopping processing on the received second optical signal to form a second optical pulse signal with pulses having a certain repetition frequency; and performs amplitude modulation on the second optical pulse signal through the second amplitude modulator 2308 , the second optical pulse signal after amplitude modulation is phase-modulated by the second phase modulator 2309, and the second optical pulse signal subjected to amplitude and phase modulation is attenuated by the second adjustable attenuator 2310 to obtain quantum Optical signal, the quantum optical signal is sent to the coupling unit 2104. Optionally, after the second pulse modulator 2307 generates the second optical pulse signal, the second optical pulse signal can also be attenuated by the second adjustable attenuator 2310, and then the amplitude and phase are modulated, and finally Obtain the reference optical signal.

In this embodiment of the present invention, the parameters in the first pulse modulator 2303 and the second pulse modulator 2307 may be predetermined, so that the frequency of the pulses included in the first optical pulse signal is greater than the frequency of the pulses included in the second optical pulse signal frequency.

The first adjustable attenuator 2306 sends the reference optical signal to the polarization beam splitter 2203, and the polarization beam splitter 2203 and the Faraday mirror 2204 are used in combination to rotate the polarization state of the received reference optical signal by a first angle, a first angle It can be 90 degrees. On the other hand, since the reference optical signal output by the first adjustable attenuator 2306 travels a distance longer than the quantum optical signal output by the second adjustable attenuator 2310, the reference optical signal The reference optical signal entering the polarization coupling unit 2201 from the polarization beam splitter 2203 has a longer time delay than the quantum optical signal entering the polarization coupling unit 2201 directly from the second adjustable attenuator 2310 . The polarization beam splitter 2203 sends the reference optical signal whose polarization state is rotated by the first angle to the polarization coupling unit 2201;

The polarization coupling unit 2201 is used to perform polarization coupling processing on the received quantum optical signal pulse and the reference optical signal whose polarization state is rotated by the first angle, so as to obtain a channel of polarization multiplexing and time division multiplexing of the reference optical signal and the quantum optical signal. The transmitted optical signal is transmitted, and the transmitted optical signal is transmitted to the receiving device.

The polarization coupling unit 2201 receives the reference optical signal rotated by the first angle and the unrotated quantum optical signal, and the polarization coupling unit 2201 mixes the polarization of the reference optical signal rotated by the first angle with the unrotated quantum optical signal orthogonally. A fiber channel is used for transmission, thereby realizing polarization multiplexing and time division multiplexing of the reference optical signal and the quantum optical signal. Optionally, the time delay of the reference optical signal compared to the quantum optical signal can also be controlled, for example, through the optical fiber or the polarization rotation unit 2202 between the first adjustable attenuator 2306 and the polarization coupling unit 2201, so that the reference light The pulse of the signal and the pulse of the quantum optical signal are evenly staggered in time, which can minimize the crosstalk between the reference optical signal and the quantum optical signal when they are transmitted in the same optical fiber channel.

Optionally, in this embodiment of the present invention, the reference optical signal is only used to enable the receiving device to determine the phase frequency information between the local oscillator optical signal and the reference optical signal. In order to improve the information transmission efficiency of the quantum key distribution process, optional In the embodiment of the present invention, the second modulation unit 2103 modulates classical information on the first optical pulse signal, so that the reference optical signal includes classical information. Classical information is some information that does not need to be kept secret in the process of quantum key distribution, so the efficiency of information transmission is improved.

Fig. 2f exemplarily shows a schematic structural diagram of a transmitting apparatus for quantum key distribution in an embodiment of the present invention. As shown in Fig. 2f, the first modulation unit 2102 includes a first pulse modulation connected to a beam splitter The in-phase quadrature modulator 2303 is connected to the first pulse modulator 2303, the first adjustable attenuator 2306 is connected to the in-phase quadrature modulator, and the first adjustable attenuator 2306 is connected to the coupling unit 2104.

As shown in FIG. 2f , the first optical pulse signal output by the first pulse modulator 2303 enters an In-phase Quadrature (IQ for short) modulator, and the in-phase quadrature modulator adopts the traditional Quadrature Phase Shift Keying (Quadrature Phase The modulation mode of Shift Keyin (QPSK for short) performs four-phase modulation on the first adjustable attenuator 2306, and modulates the classical information to be encoded onto the reference optical signal.

It can be seen from the above content that, in the embodiment of the present invention, since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal, the pulse of the quantum optical signal and the adjacent reference light The time interval between the pulses of the signal is small, and when the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and then according to the phase between the pulse of the reference optical signal and the local oscillator optical signal The frequency information will reduce the error when estimating the phase-frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then use the phase-frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error to be used to quantify the quantum optical signal. The modulation of the local oscillator optical signal in which the optical signal is coherently coupled will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

Fig. 3a exemplarily shows a schematic structural diagram of a receiving apparatus for quantum key distribution provided by an embodiment of the present invention.

Based on the above-mentioned system architecture and the same concept, as shown in FIG. 3a, a receiving apparatus provided by an embodiment of the present invention includes a coherent coupling unit 3101, a reference light balance detection unit 3102 connected to the coherent coupling unit 3101, and a quantum light balance detection unit 3102 Unit 3103, the carrier recovery unit 3104 connected to the reference optical balance detection unit 3102, the key recovery unit 3105 connected to the quantum optical balance detection unit 3103, the coherent coupling unit is also connected to the local oscillator unit 3201, the local oscillator unit 3201 and the carrier recovery unit 3104 connect;

The coherent coupling unit 3101 is used to perform spectral processing on the received transmission optical signal including the reference optical signal and the quantum optical signal, and perform coherent coupling on the transmission optical signal after the spectral processing according to the local oscillator optical signal, so as to obtain the reference optical signal including the reference optical signal. The first coherently coupled optical signal of the signal and the second coherently coupled optical signal including the quantum optical signal; the first coherently coupled optical signal is sent to the reference optical balance detection unit 3102, and the second coherently coupled optical signal is sent To the quantum optical balance detection unit 3103; wherein, the pulse appearance frequency of the reference optical signal included in the optical signal after the first coherent coupling is the first frequency, and the pulse appearance frequency of the quantum optical signal included in the optical signal after the second coherent coupling is the second frequency, the first frequency is greater than the second frequency;

The local oscillator unit 3201 is used to generate a local oscillator optical signal and send the local oscillator optical signal to the coherent coupling unit 3101;

The reference optical balance detection unit 3102 is used to perform photoelectric conversion on the first coherently coupled optical signal, perform differential processing and amplification, obtain the first electrical signal, and transmit the first electrical signal to the carrier recovery unit 3104;

The quantum optical balance detection unit 3103 is used to perform photoelectric conversion on the second coherently coupled optical signal, perform differential processing and amplification, obtain the second electrical signal, and transmit the second electrical signal to the key recovery unit 3105;

a carrier recovery unit 3104, configured to determine the phase frequency information between the local oscillator optical signal and the reference optical signal from the first electrical signal;

The key recovery unit 3105 is configured to recover the original key from the second electrical signal according to the received phase frequency information.

Specifically, in the embodiment of the present invention, the key recovery unit 3105 recovers the original key from the second electrical signal according to the received phase frequency information. The phase frequency information between the quantum optical signal and the local oscillator optical signal, such as the phase difference, is then used to estimate the phase frequency information between the quantum optical signal and the local oscillator optical signal according to the phase frequency information between the reference optical signal and the local oscillator optical signal, and then use the quantum optical signal and the local oscillator. The phase frequency information between the oscillatory optical signals modulates the phase compensation of the local oscillator optical signal used for coherent coupling of the quantum optical signal, and then uses the modulated local oscillator optical signal to coherently couple with the quantum optical signal, and from the coherent coupling The original key is recovered from the post-quantum optical signal.

Since the frequency of the pulses included in the first optical pulse signal is greater than the frequency of the pulses included in the second optical pulse signal, the time interval between the pulse of the quantum optical signal and the pulse of the adjacent reference optical signal is small. For example, for example, a pulse of a reference optical signal every 2 seconds and a pulse of a quantum optical signal every 20 seconds. At this time, since the reference optical signal and the quantum optical signal are time-division multiplexed, the pulse of the quantum optical signal should be located between two pulses. Between pulses of adjacent reference optical signals, the time interval between pulses of two adjacent reference optical signals is 2 seconds, so the time interval between the quantum optical signal and the reference optical signal adjacent to the quantum optical signal can be 1 second . It can be seen that the higher the frequency of occurrence of the pulses of the reference optical signal, the shorter the time interval between the pulses of the adjacent reference optical signals, and the shorter the time interval between the quantum optical signal and its adjacent reference optical signal. . Then, when the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and then estimates the pulse and the local oscillator of the quantum optical signal according to the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal. The phase frequency information between the optical signals will reduce the error, and then according to the phase frequency information between the pulse of the quantum optical signal with the reduced error and the local oscillator optical signal, the local oscillator optical signal used for coherently coupling the quantum optical signal is determined. The modulation will be more accurate, and the original key recovered from the coherently coupled quantum light signal will be more accurate.

Since the reference light balance detection unit 3102 and the quantum light balance detection unit 3103 are respectively used in the embodiment of the present invention, the reference light balance detection unit 3102 can be used to perform coherent detection on the reference light signal in the transmitted light signal, and the quantum light The balance detection unit 3103 performs coherent detection on the quantum optical signal in the transmission optical signal, and then the parameters of the reference optical balance detection unit 3102 and the quantum optical balance detection unit 3103 can be set respectively. Optionally, the bandwidth of the reference light balance detection unit 3102 is higher than the bandwidth of the quantum light balance detection unit 3103 ; the gain of the reference light balance detection unit 3102 is lower than the gain of the quantum light balance detection unit 3103 .

In the embodiment of the present invention, optionally, the reference optical signal and the quantum optical signal included in the transmission optical signal are polarization multiplexed; for example, as shown in the structural diagram of the transmission light shown in FIG. 2b. At this time, FIG. 3b exemplarily shows a schematic structural diagram of a receiving apparatus for quantum key distribution provided by an embodiment of the present invention. As shown in FIG. 3b, the coherent coupling unit 3101 includes a polarization beam splitting unit 5401, a first sub-coherent coupling unit 5502 and a second sub-coherent coupling unit 5503 connected to the polarization beam splitting unit 5401, and the first sub-coherent coupling unit 5502 is connected to the reference light The balance detection unit 3102 and the second sub-coherent coupling unit 5503 are connected to the quantum light balance detection unit 3103 .

The local oscillator unit 3201 is used to generate a local oscillator optical signal, and divide the local oscillator optical signal into a first sub-local oscillator optical signal and a second sub-local oscillator optical signal; send the first sub-local oscillator optical signal to the first sub-local oscillator optical signal Coherent coupling unit 5502; sending the second sub-local oscillator optical signal to the second sub-coherent coupling unit 5503;

The polarization beam splitting unit 5401 is used to divide the transmission optical signal into a first split-processed optical signal including a reference optical signal and a second split-processed optical signal including a quantum optical signal through polarization split processing;

The first sub-coherent coupling unit 5502 is configured to use the first sub-local oscillator optical signal to perform coherent coupling on the optical signal after the first splitting process, and output the first optical signal after coherent coupling;

The second sub-coherent coupling unit 5503 is configured to use the second sub-local oscillator optical signal to perform coherent coupling on the second optical signal after splitting processing, and output the second optical signal after coherent coupling.

FIG. 3b also exemplarily shows a possible schematic structural diagram of the local oscillator unit 3201 in the embodiment of the present invention. As shown in FIG. 3b, the local oscillator unit 3201 includes a local oscillator optical splitting unit 4501, a first local oscillator modulation unit 4502 and a second local oscillator modulation unit 4503 connected to the local oscillator optical splitting unit 4501, and the first local oscillator modulation unit 4502 is connected to the first sub-coherent coupling unit 5502; the second local oscillator modulation unit 4503 is connected to the second sub-coherent coupling unit 5503; optionally, the local oscillator light splitting unit 4501 can be a polarization beam splitter 4401;

The local oscillator optical splitting unit 4501 is configured to divide the generated local oscillator optical signal into a third sub-local oscillator optical signal and a fourth sub-local oscillator optical signal, and send the third sub-local oscillator optical signal to the first local oscillator modulation unit 4502, the fourth sub-local oscillator optical signal is sent to the second local oscillator modulation unit 4503; the polarization state of the third sub-local oscillator optical signal and the optical signal after the first splitting process are consistent, and the fourth sub-local oscillator optical signal and the second The polarization state of the optical signal after the splitting process is consistent;

The first local oscillator modulation unit 4502 is used for chopping the third sub-local oscillator optical signal to obtain the first optical pulse local oscillator signal; and performing phase modulation on the first optical pulse local oscillator signal to obtain the first sub-sub version The vibration optical signal; the frequency of the pulse included in the first optical pulse local oscillator signal is the first frequency;

The second local oscillator modulation unit 4503 is configured to perform chopping processing on the fourth sub-local oscillator optical signal to obtain a second optical pulse local oscillator signal; and phase-phase the second optical pulse local oscillator signal according to the received phase frequency information Modulation is performed to obtain a second sub-local oscillator optical signal; the frequency of the pulse included in the second optical pulse local oscillator signal is the second frequency.

Optionally, the local oscillator optical signal includes a first local oscillator optical signal used for fitting the reference optical signal in the transmission optical signal, and a second local oscillator optical signal used for fitting the quantum optical signal in the transmission optical signal. vibrating optical signal; the phase of the first local vibrating optical signal is a preset fixed phase value; the phase of the second local vibrating optical signal is calculated after the phase frequency information determined by the carrier recovery unit for selecting the measurement base A random one of the two phase values of .

Optionally, the first local oscillation modulation unit 4502 is further configured to:

delaying the first optical pulse local oscillator signal in the time domain, so that the pulse in the obtained first sub-local oscillator optical signal corresponds in the time domain with the pulse of the reference optical signal included in the optical signal after the first spectral processing; and perform phase modulation on the local oscillator signal of the first optical pulse delayed in the time domain;

The second local oscillator modulation unit 4503 is also used for:

delaying the second optical pulse local oscillator signal in the time domain, so that the pulse in the second sub-local oscillator optical signal obtained corresponds in the time domain with the pulse of the quantum optical signal included in the optical signal after the second spectral processing; Phase modulation is performed on the local oscillator signal of the second optical pulse delayed in the time domain.

As shown in FIG. 3b, optionally, the coherent coupling unit 3101 is further connected to the polarization control unit 3301. Specifically, the transmitting device transmits a transmission optical signal to the receiving device through the optical fiber, the transmission optical signal first enters the polarization control unit 3301, and the polarization state of the transmission optical signal before entering the polarization control unit 3301 changes in real time, At this time, through the polarization control unit 3301, the polarization state of the transmitted optical signal can be tracked and adjusted in real time, so that the reference optical signal and the quantum optical signal in the transmitted optical signal output to the coherent coupling unit 3101 are still positively positive. cross-polarized state. Optionally, the polarization control unit 3301 may be a dynamic polarization controller.

As shown in FIG. 3 b , the carrier recovery unit 3104 includes a first ADC unit 3302 connected to the reference light balance detection unit 3102 , and a first processing unit 3303 connected to the first ADC unit 3302 . The key recovery unit 3105 includes a second ADC unit 3304 connected to the quantum light balance detection unit 3103 , and a second processing unit 3305 connected to the second ADC unit 3304 .

The first ADC unit 3302 is used for receiving the first electrical signal, sampling and quantizing the first electrical signal, obtaining a reference signal sampling sequence, and sending the reference signal sampling sequence to the first processing unit 3303; the first coherently coupled light The electrical signal amplitude corresponding to the reference optical signal included in the signal in the corresponding first electrical signal is within the first preset amplitude range of the first ADC unit 3302;

The first processing unit 3303 determines the phase frequency information between the local oscillator optical signal and the reference optical signal according to the received reference signal sampling sequence, and sends the phase frequency information to the second local oscillator modulation unit 4503 .

The second ADC unit 3304 is configured to receive the second electrical signal, sample and quantify the second electrical signal, obtain a quantum signal sampling sequence, and send the quantum signal sampling sequence to the second processing unit 3305; each second coherent coupling The electrical signal amplitude corresponding to the quantum optical signal included in the rear optical signal in the corresponding second electrical signal is within the second preset amplitude range of the second ADC unit 3304;

The second processing unit 3305 recovers the original key according to the received quantum signal sampling sequence.

In a specific implementation, the first ADC unit 3302 may include one or more ADCs, and the second ADC unit 3304 may include one or more ADCs. The first preset amplitude range of the first ADC unit 3302 is an amplitude range in which the ADC included in the first ADC unit 3302 can perform sampling and quantization, and the second preset amplitude range of the second ADC unit 3304 is the second ADC A range of amplitudes over which the ADC included in unit 3304 can perform sample quantization.

Fig. 3c exemplarily shows a schematic structural diagram of a receiving device for quantum key distribution provided by an embodiment of the present invention. As shown in Fig. 3c, the local oscillator light splitting unit 4501 includes a local oscillator laser 4201, and a local oscillator laser 4201 is connected to the polarization beam splitter 4401; the polarization beam splitter 4401 is respectively connected to the third pulse modulator 4402 in the first local oscillation modulation unit 4502 and the fourth pulse modulator 4405 in the second local oscillation modulation unit 4503, the third The pulse modulator 4402 is connected to the first delay device 4403, the first delay device 4403 is connected to the first local oscillator phase modulator 4404, and the first local oscillator phase modulator 4404 is connected to the first sub-coherent coupling unit 5502; the fourth pulse modulator 4405 is connected to the second delayer 4406, the second delayer 4406 is connected to the second local oscillator phase modulator 4407, the second local oscillator phase modulator 4407 is connected to the second sub-coherent coupling unit 5503; the signal generator 4408 is connected to the carrier recovery unit The first processing unit 3303 of 3104, as well as the third pulse modulator 4402, the fourth pulse modulator 4405, the first delayer 4403 and the second delayer 4406.

When the reference optical signal and the quantum optical signal are transmitted through polarization multiplexing, the reference optical signal is in the Y polarization state, and the quantum optical signal is in the X polarization state. The polarization beam splitting unit 5401 receives the optical signal output by the polarization control unit 3301, and divides it into a quantum optical signal transmitted in the X polarization state and a reference optical signal transmitted in the Y polarization state, that is, the first output of the polarization beam splitting unit 5401. The polarization states of the optical signal after the splitting processing and the optical signal after the second splitting processing are inconsistent. At this time, the polarization states of the first sub-LO optical signal and the second sub-LO optical signal output by the local oscillator optical splitting unit 4501 are also inconsistent. Specifically, for example, the local oscillator optical splitting unit 4501 can input the input to the first local oscillator modulation unit The polarization state of the first sub-local oscillator optical signal of 4502 is rotated, so that the polarization state of the first sub-local oscillator optical signal and the polarization state of the reference optical signal are consistent, both are Y polarization states, and X polarization states are the default polarization states , that is, the polarization state of the second sub-local oscillator optical signal output by the local oscillator optical splitting unit 4501 is the X polarization state, so there is no need to rotate the polarization state of the second sub-local oscillator optical signal to ensure the second sub-local oscillator optical signal. The polarization state of the sub-local oscillator optical signal is consistent with the polarization state of the quantum optical signal.

In another optional embodiment, as shown in FIG. 3b , the reference optical signal is in the Y polarization state, and the quantum optical signal is in the X polarization state, and the polarization splitting unit 5401 in the coherent coupling unit 3101 receives the output of the polarization control unit 3301 The optical signal is divided into the quantum optical signal transmitted in the X polarization state, and the polarization state of the reference optical signal transmitted in the Y polarization state is rotated, so that the first spectrally processed light output by the polarization beam splitting unit 5401 The polarization state of the signal and the optical signal after the second splitting process are consistent, for example, both are in the X polarization state. At this time, the local oscillator optical splitting unit 4501 is used to divide the generated local oscillator optical signal into a third sub-local oscillator optical signal and a fourth sub-local oscillator optical signal, and send the third sub-local oscillator optical signal to the first local oscillator modulation The unit 4502 sends the fourth sub-local oscillator optical signal to the second local oscillator modulation unit 4503, and does not perform any adjustment on the polarization states of the third sub-local oscillator optical signal and the fourth sub-local oscillator optical signal. At this time, the polarization states of the third sub-local oscillator optical signal and the fourth sub-local oscillator optical signal generated by the local oscillator optical splitting unit 4501 are consistent, and the polarization states of the third sub-local oscillator optical signal and the optical signal after the first splitting process Consistent, the polarization states of the fourth sub-local oscillator optical signal and the second optical signal after splitting processing are the same. At this time, the local oscillator wind-solar unit in FIG. 3b may only include the local oscillator laser 4201 and a spectroscope, and the third sub-local oscillator optical signal and the fourth sub-local oscillator optical signal separated by the optical splitter enter the third sub-local oscillator optical signal respectively. Pulse striping before and in the fourth pulse modulator 4405.

Optionally, if classical information is also modulated in the reference optical signal in the transmission optical signal, the reference optical balance detection unit 3102 in this embodiment of the present invention is further configured to perform in-phase quadrature IQ detection on the first electrical signal, and The first electrical signal that has undergone IQ detection is transmitted to the carrier recovery unit 3104; the carrier recovery unit 3104 is further configured to demodulate the classical information modulated on the reference optical signal from the first electrical signal that has undergone IQ detection. In this way, the utilization rate of the reference optical signal can be improved.

In order to more clearly describe the working principle of the receiving apparatus in the embodiment of the present invention, a detailed description is given below with reference to FIG. 3c. Taking the reference optical signal and the quantum optical signal in the transmitted optical signal to be transmitted to the receiving device through polarization multiplexing and time division multiplexing as an example, and the polarization states of the reference optical signal and the quantum optical signal are orthogonal, and the reference optical signal is transmitted through the Y polarization state, Quantum light signals are transmitted through the X polarization state.

The transmitting device transmits a transmission optical signal to the receiving device through the optical fiber, the transmission optical signal first enters the polarization control unit 3301, and the polarization state of the transmission optical signal entering the polarization control unit 3301 changes in real time. The polarization control unit 3301 can track and adjust the polarization state of the transmission optical signal in real time, so that the transmission optical signal output to the coherent coupling unit 3101 has a certain polarization state. Optionally, the polarization control unit 3301 may be a dynamic polarization controller. With reference to the specific example, the polarization states of the reference optical signal and the quantum optical signal in the optical signal output by the polarization control unit 3301 are still orthogonal.

The optical signal output by the polarization control unit 3301 enters the polarization beam splitting unit 5401, and the polarization beam splitting unit 5401 divides the transmitted optical signal into the first split-processed optical signal including the reference optical signal and the second optical signal including the quantum optical signal through polarization splitting processing. The polarization state of the optical signal after the two-splitting process is still the Y polarization state, and the polarization state of the optical signal after the second light-splitting process is still the X polarization state. It can be seen that the polarization demultiplexing of the optical signals transmitted in the two polarization states is performed by the polarization splitting unit 5401, and the purpose of transmitting the optical signals of different polarization states in different fibers can be realized at this time. After the first splitting process, the optical signal enters the first sub-coherent coupling unit 5502 , and after the second splitting process, the optical signal enters the second sub-coherent coupling unit 5503 . Optionally, the first sub-coherent coupling unit 5502 and the second sub-coherent coupling unit 5503 may both be 2:2 couplers.

The local oscillator laser 4201 in the local oscillator unit 3201 generates a local oscillator light signal, which is divided into a third sub-local oscillator light signal and a fourth sub-local oscillator light signal by the polarization beam splitter 4401, and the third sub-local oscillator light signal is divided into It is sent to the first local oscillator modulation unit 4502, and the fourth sub-local oscillator optical signal is sent to the second local oscillator modulation unit 4503; The polarization states of the sub-local oscillator optical signal and the optical signal after the second splitting process are consistent. That is to say, the polarization beam splitter 4401 rotates the polarization state of the third sub-local oscillator optical signal, so that the polarization state of the third sub-local oscillator optical signal is the Y polarization state. The polarization state of the vibrating signal is the X polarization state.

Afterwards, the third pulse modulator 4402 in the first local oscillator modulation unit 4502 performs chopping processing on the third sub-local oscillator optical signal to obtain the first optical pulse local oscillator signal; The oscillating signal is delayed in the time domain, so that the pulses in the obtained first sub-local oscillator optical signal correspond in the time domain with the pulses of the reference optical signal included in the optical signal after the first spectral processing; the first local oscillator phase modulation The device 4404 performs phase modulation on the first optical pulse local oscillator signal delayed in the time domain to obtain a first sub-local oscillator optical signal; the frequency of the pulse included in the first optical pulse local oscillator signal is the first frequency.

After that, the fourth pulse modulator 4405 in the second local oscillator modulation unit 4503 performs chopping processing on the fourth sub-local oscillator optical signal to obtain the second optical pulse local oscillator signal; The vibration signal is delayed in the time domain, so that the pulses in the obtained second sub-local oscillator optical signal correspond in the time domain to the pulses of the quantum optical signal included in the optical signal after the second spectral processing; the second local oscillator phase modulation The device 4407 performs phase modulation on the second optical pulse local oscillator signal delayed in the time domain to obtain a second sub-local oscillator optical signal; the frequency of the pulse included in the second optical pulse local oscillator signal is the second frequency. The light intensities of the first sub-local oscillator optical signal and the second sub-local oscillator optical signal can be adjusted to be consistent, or can be adjusted to be inconsistent.

Further, ideally, the local oscillator optical signal output by the local oscillator unit 3201 and the local oscillator optical signal received by the coherent coupling unit 3101 are of the same frequency and phase, but in the actual operating system, the local oscillator unit 3201 and the optical signal generation unit 2101 They are located in two places, and their output frequencies are controlled separately, so there is no guarantee that their frequencies are exactly the same, let alone that their phases are exactly the same. At the same time, the change of the limited external ambient temperature will cause the length of the optical fiber to change, which will inevitably cause disturbance to the system, resulting in a new phase difference. In order to ensure the phase relationship between the local oscillator optical signal received at the input end of the coherent coupling unit 3101 and the transmission optical signal input by the polarization control unit 3301 , the signal generator 4408 needs to receive the synchronization output from the first processing unit 3303 Clock parameters, as well as phase frequency information, such as phase difference compensation parameters and frequency offset compensation parameters, the phase difference compensation parameters are phase difference compensation parameters, and then the signal generator 4408 adjusts the input in real time to the third pulse modulator 4402 and the fourth pulse modulator 4405 and the phase modulation signal input to the phase modulator, so as to achieve real-time adjustment of the measurement base signal input to the second local oscillator phase modulator 4407.

The first sub-coherent coupling unit 5502 and the reference optical balance detection unit 3102 perform balanced zero-beat detection on the first sub-local oscillator optical signal and the first first split-processed optical signal, and the first sub-coherent coupling unit 5502 may be 2:2 The coupler, the reference light balance detection unit 3102 can be a balanced receiver. The carrier recovery unit 3104 determines the phase frequency information between the reference optical signal and the local oscillator optical signal through the balance detection result.

The principle of balanced zero-beat detection is as follows:

In a quantum system, the result of coherent detection for a reference optical signal can be expressed by formula (1):

……Formula 1)

In formula (1), θ is the equivalent phase difference between the reference optical signal and the local oscillator optical signal; X _r and P _r are the modulated parameters of the reference optical signal itself (in the quantum key distribution system, X _r and P r _r is set as a parameter known to both the transmitting device and the receiving device); I _r is the current value output by the reference optical balance detection unit 3102; I _L0 is the first sub-local oscillator optical signal input to the first sub-coherent coupling unit 5502 The light intensity; ∝ is the proportional symbol.

The phase difference between the reference optical signal and the local oscillator optical signal can be determined by the above formula (1).

After the phase difference between the reference optical signal and the local oscillator optical signal is determined, according to the phase difference between the reference optical signal and the local oscillator optical signal, the second sub-local oscillator used for balanced zero-beat detection with the quantum optical signal The optical signal is phase-modulated, so that the phase of the second sub-local oscillator optical signal and the quantum optical signal is 0 or π/2.

The estimation of the phase difference in the embodiment of the present invention requires careful theoretical deduction. This is because the local oscillator light signal and the quantum light signal are light emitted by different light sources, and there is a certain frequency difference between them, which will affect the local oscillator light. The phase difference between the signal and the quantum optical signal has an effect, and the phase difference θ between the local oscillator optical signal and the reference optical signal in formula (1) cannot be directly replaced by the phase difference between the local oscillator optical signal and the quantum optical signal.

The coherent detection result of bringing the frequency difference into the reference optical signal can be approximately expressed as formula (2):

……公式(2)

...formula (2)

是额外加载在本振光信号上的相位调制；X_s为调制在量子光信号上的正则位置参数；P_s为调制在量子光信号上的正则动量参数；I_s为量子光平衡探测单元3103输出的电流值；I_L0为输入第二子相干耦合单元5503的第二子本振光信号的光强；∝为正比例符号；·为乘以。In formula (2), Δω is the frequency difference between the local oscillator optical signal and the quantum optical signal; t is the time interval between the reference optical signal and the adjacent quantum optical signal, and θ is the equivalent phase difference between the reference optical signal and the local oscillator optical signal ;

is the phase modulation additionally loaded on the local oscillator optical signal; X _s is the canonical position parameter modulated on the quantum optical signal; P _s is the canonical momentum parameter modulated on the quantum optical signal; I _s is the quantum optical balance detection unit 3103 The output current value; I _L0 is the light intensity of the second sub-local oscillator optical signal input to the second sub-coherent coupling unit 5503; ∝ is the proportional symbol; · is the multiplication.

In the quantum key distribution system, the purpose of modulating the phase of the local oscillator light so that the phases of the local oscillator light signal and the quantum light signal are 0 or π/2 is to simplify formula (2) into formula (3) or Any of the formulas in formula (4), but this absolute simplification cannot be done because of the uncertain value of the frequency difference.

……公式(3)

...formula (3)

In formula (3), X _s is the canonical position parameter modulated on the quantum light signal; I _s is the current value output by the quantum light balance detection unit ₃₁₀₃ ; The light intensity of the local oscillator optical signal; ∝ is the proportional symbol.

……公式(4)

...Equation (4)

In formula (4), P _s is the canonical momentum parameter modulated on the quantum light signal _; Is is the current value output by the quantum light balance detection unit ₃₁₀₃ ; The light intensity of the local oscillator optical signal; ∝ is the proportional symbol.

To evaluate the influence of the frequency difference on the detection result, it is necessary to know the size of Δω·t in the above formula (2). The difference in frequency between the light emitted by two different lasers can be measured by a spectrometer. At the current technical level, the resolution of the spectrometer can only be up to 5MHz, so for the frequency difference of the light emitted by two different lasers, the instrument detection can only measure the order of 10MHz, so it can be considered that the upper limit of the frequency difference : Δω<10 MHz (the actual value of Δω changes in real time).

如果能够满足的条件下，由频率差引起的相位变化影响就可以相对地忽略，通过数值计算可以得到t≤10 ns的结论。Analyze the phase difference between the local oscillator light and the quantum light signal in formula (2):

if satisfied Under the condition of , the influence of the phase change caused by the frequency difference can be relatively ignored, and the conclusion that t≤10 ns can be obtained by numerical calculation.

For example, the repetition frequency of the selected quantum optical signal pulse is 100MHz, and the repetition frequency of the reference pulse is 500MHz. After polarization multiplexing and time division multiplexing, the interval time between the reference pulse and the signal pulse is 1ns. From this, it can be calculated that Δω·t<0.01, which is a very small quantity and can be ignored in numerical calculation, so that the coherent detection result of the signal pulse can be approximately expressed as formula (5):

……公式(5)

...formula (5)

是额外加载在本振光信号上的相位调制；X_s为调制在量子光信号上的正则位置参数；P_s为调制在量子光信号上的正则动量参数；I_s为量子光平衡探测单元3103输出的电流值；I_L0为输入第二子相干耦合单元5503的第二子本振光信号的光强；∝为正比例符号。In formula (5), θ is the equivalent phase difference between the reference optical signal and the local oscillator optical signal;

is the phase modulation additionally loaded on the local oscillator optical signal; X _s is the canonical position parameter modulated on the quantum optical signal; P _s is the canonical momentum parameter modulated on the quantum optical signal; I _s is the quantum optical balance detection unit 3103 The output current value; I _L0 is the light intensity of the second sub-local oscillator optical signal input to the second sub-coherent coupling unit 5503; ∝ is the proportional symbol.

by choosing the appropriate The above formula (5) can be simplified to formula (3) or formula (4), which is the selective measurement of the two modulation parameters of the signal pulse.

In the theoretical analysis of estimating the phase difference, a random phase change δθ needs to be added, which is caused by the disturbance of the external environment. Because there is a time interval between the reference optical signal and the quantum optical signal, even if both of them are transmitted from the sending device to the receiving device through the same channel, the random interference introduced by the external environment will cause a difference in phase change between the two during the transmission process. . If the time interval is longer, the random phase change δθ may become very large, which will make the phase estimation error very large, even if the phase of the two reference optical signals before and after the quantum optical signal and the local oscillator optical signal are used. The method of estimating the phase difference between the intermediate quantum optical signal and the local oscillator optical signal by using the average value of the difference also cannot eliminate the influence of random phase variation δθ. In the above example of the embodiment of the present invention, the interval between the reference optical signal and the quantum optical signal is only 1 ns, while the interval between the reference optical signal and the quantum optical signal in the prior art is 50 ns. Therefore, in the embodiment of the present invention, the external environment affects the signal The random phase change δθ during the transmission process will be smaller, thus, the embodiments of the present invention improve the accuracy and precision of the determined phase information of the quantum optical signal and the local oscillator optical signal.

Furthermore, the second local oscillator modulation unit 4503 in the embodiment of the present invention can more accurately modulate the phase of the second sub-local oscillator optical signal according to the more accurate and precise quantum optical signal and the phase information of the local oscillator optical signal, so as to adjust the phase of the quantum optical signal more accurately. The optical signal is subjected to selective basis measurement, thereby recovering a more accurate and precise original key from the quantum optical signal.

It can be seen from the above content that, in the embodiment of the present invention, since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal, the pulse of the quantum optical signal and the adjacent reference light The time interval between the pulses of the signal is small, and when the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and then according to the phase between the pulse of the reference optical signal and the local oscillator optical signal The frequency information will reduce the error when estimating the phase-frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then use the phase-frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error to be used to quantify the quantum optical signal. The modulation of the local oscillator optical signal in which the optical signal is coherently coupled will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

FIG. 4 exemplarily shows a schematic flowchart of a quantum key distribution method provided by an embodiment of the present invention.

Based on the same concept, an embodiment of the present invention provides a quantum key distribution method, which can be implemented by the sending device in the above content, as shown in FIG. 4 , including:

Step 401, the transmitting device performs spectral processing on the generated optical signal to obtain a first optical signal and a second optical signal;

Step 402, the sending device performs chopping processing on the first optical signal to obtain a first optical pulse signal; and attenuates and modulates the first optical pulse signal to obtain a reference optical signal;

Step 403: The sending device performs chopping processing on the second optical signal to obtain a second optical pulse signal; attenuates and modulates the second optical pulse signal to obtain a quantum optical signal; the frequency of the pulse included in the first optical pulse signal greater than the frequency of the pulses included in the second optical pulse signal;

Step 404 , the sending device performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, and transmits the transmission optical signal to the receiving device.

Optionally, the sending device performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, including:

Rotate the polarization state of the received reference optical signal by a first angle; perform polarization coupling processing on the received quantum optical signal pulse and the reference optical signal whose polarization state is rotated by the first angle, to obtain the polarization complex of the reference optical signal and the quantum optical signal. A transmission optical signal to be transmitted is used and time-division multiplexed;

or,

Rotate the polarization state of the received quantum optical signal by a second angle; perform polarization coupling processing on the received reference optical signal pulse and the quantum optical signal whose polarization state is rotated by the second angle to obtain the polarization complex of the reference optical signal and the quantum optical signal. A transmission optical signal to be sent is used and time-division multiplexed.

Optionally, before the sending device performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted including the reference optical signal and the quantum optical signal, the sending device is further used for:

The classical information is modulated on the first optical pulse signal, so that the classical information is included in the reference optical signal.

It can be seen from the above content that, in the embodiment of the present invention, since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal, the pulse of the quantum optical signal and the adjacent reference light The time interval between the pulses of the signal is small, and when the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and then according to the phase between the pulse of the reference optical signal and the local oscillator optical signal The frequency information will reduce the error when estimating the phase-frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, and then use the phase-frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error to be used to quantify the quantum optical signal. The modulation of the local oscillator optical signal in which the optical signal is coherently coupled will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

FIG. 5 exemplarily shows a schematic flowchart of a quantum key distribution method provided by an embodiment of the present invention.

Based on the same concept, an embodiment of the present invention provides a quantum key distribution method, which can be implemented by the sending device in the above content, as shown in FIG. 5 , including:

Step 501, the receiving device generates a local oscillator optical signal, performs spectral processing on the received transmission optical signal including the reference optical signal and the quantum optical signal, and performs coherent coupling on the optically split transmission signal according to the local oscillator optical signal, Obtaining a first coherently coupled optical signal including a reference optical signal and a second coherently coupled optical signal including a quantum optical signal; wherein the pulse appearance frequency of the reference optical signal included in the first coherently coupled optical signal is the first frequency , the pulse appearance frequency of the quantum optical signal included in the optical signal after the second coherent coupling is the second frequency, and the first frequency is greater than the second frequency;

Step 502, the receiving device performs photoelectric conversion on the first coherently coupled optical signal, performs differential processing and amplification to obtain a first electrical signal; performs photoelectric conversion on the second coherently coupled optical signal, performs differential processing and amplification, and obtains a second optical signal. electric signal;

Step 503, the receiving device determines the phase frequency information between the local oscillator optical signal and the reference optical signal from the first electrical signal, and recovers the original key from the second electrical signal according to the phase frequency information.

According to the phase frequency information, the original key is recovered from the second electrical signal. The specific principle is as follows:

The local oscillator optical signal used for coherent coupling of the quantum optical signal is modulated using the phase frequency information, and the modulated local oscillator optical signal is then used for coherent coupling with the quantum optical signal and recovered from the coherently coupled quantum optical signal out the original key.

Optionally, polarization multiplexing of the reference optical signal and the quantum optical signal included in the transmission optical signal;

The receiving device generates a local oscillator optical signal, performs spectroscopic processing on the received transmission optical signal including the reference optical signal and the quantum optical signal, and performs coherent coupling on the transmitted optical signal after the spectroscopic processing according to the local oscillator optical signal, to obtain the reference optical signal including the reference optical signal and the quantum optical signal. The first coherently coupled optical signal of the optical signal and the second coherently coupled optical signal including the quantum optical signal include:

The receiving device generates a local oscillator optical signal, and divides the local oscillator optical signal into a first sub-local oscillator optical signal and a second sub-local oscillator optical signal;

The receiving device divides the transmission optical signal into a first spectrally processed optical signal including a reference optical signal and a second spectrally processed optical signal including a quantum optical signal by polarization splitting processing;

The receiving device uses the first sub-local oscillator optical signal to coherently couple the optical signal after the first splitting process, and outputs the first coherently coupled optical signal; and uses the second sub-local oscillator optical signal to coherently couple the second splitting-processed optical signal , and output the second coherently coupled optical signal.

Optionally, the receiving device generates a local oscillator optical signal, and divides the local oscillator optical signal into a first sub-local oscillator optical signal and a second sub-local oscillator optical signal, including;

The receiving device divides the generated local oscillator optical signal into a third sub-local oscillator optical signal and a fourth sub-local oscillator optical signal; the third sub-local oscillator optical signal and the polarization state of the optical signal after the first splitting process are consistent, and the fourth sub-local oscillator optical signal has the same polarization state. The polarization states of the local oscillator optical signal and the optical signal after the second splitting process are consistent;

The receiving device performs chopping processing on the third sub-local oscillator optical signal to obtain a first optical pulse local oscillator signal; and performs phase modulation on the first optical pulse local oscillator signal to obtain a first sub-local oscillator optical signal; the first optical pulse The frequency of the pulse included in the local oscillator signal is the first frequency;

The receiving device performs chopping processing on the fourth sub-local oscillator optical signal to obtain a second optical pulse local oscillator signal; and performs phase modulation on the second optical pulse local oscillator signal according to the phase frequency information to obtain a second sub-local oscillator optical signal; The frequency of the pulse included in the second optical pulse local oscillator signal is the second frequency.

Optionally, the receiving device performs chopping processing on the third sub-local oscillator optical signal to obtain the first optical pulse local oscillator signal, and before performing phase modulation on the first optical pulse local oscillator signal, further comprising:

delaying the first optical pulse local oscillator signal in the time domain, so that the pulse in the obtained first sub-local oscillator optical signal corresponds in the time domain with the pulse of the reference optical signal included in the optical signal after the first spectral processing;

The receiving device performs chopping processing on the fourth sub-local oscillator optical signal to obtain the second optical pulse local oscillator signal and before performing phase modulation on the second optical pulse local oscillator signal, further comprising:

The second optical pulse local oscillator signal is delayed in the time domain, so that the pulse in the second sub-local oscillator optical signal obtained corresponds in the time domain with the pulse of the quantum optical signal included in the optical signal after the second spectral processing.

Optionally, after the receiving device performs photoelectric conversion on the first coherently coupled optical signal and performs differential processing and amplification to obtain the first electrical signal, the method further includes:

In-phase quadrature IQ detection is performed on the first electrical signal, and classical information modulated on the reference optical signal is demodulated from the IQ-detected first electrical signal.

It can be seen from the above content that, in the embodiment of the present invention, since the frequency of the pulse included in the first optical pulse signal is greater than the frequency of the pulse included in the second optical pulse signal, the pulse of the quantum optical signal and the adjacent reference optical signal The time interval between the pulses is small, and when the receiving device measures the phase frequency information between the pulse of the reference optical signal and the local oscillator optical signal, and then according to the phase frequency between the pulse of the reference optical signal and the local oscillator optical signal When estimating the phase frequency information between the pulse of the quantum optical signal and the local oscillator optical signal, the error will be reduced, and then according to the phase frequency information pair between the pulse of the quantum optical signal and the local oscillator optical signal with the reduced error, the phase frequency information pair is used to analyze the quantum optical signal. The modulation of the local oscillator optical signal in which the signal is coherently coupled will be more accurate, and the original key recovered from the coherently coupled quantum optical signal will be more accurate.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, or as a computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention 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, etc.) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

The computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory result in an article of manufacture comprising the instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on 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 provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

Although preferred embodiments of the present invention have been described, additional changes and modifications to these embodiments may occur to those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be construed to include the preferred embodiment and all changes and modifications that fall within the scope of the present invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Thus, provided that these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (17)

1. A transmitting apparatus for quantum key distribution, comprising:

the optical signal generating unit is used for carrying out optical splitting processing on the generated optical signal to obtain a first optical signal and a second optical signal; sending the first optical signal to a first modulation unit, and sending the second optical signal to a second modulation unit;

the first modulation unit is used for carrying out chopping processing on the first optical signal to obtain a first optical pulse signal; attenuating and modulating the first optical pulse signal to obtain a reference optical signal, and sending the reference optical signal to a coupling unit;

the second modulation unit is used for carrying out chopping processing on the second optical signal to obtain a second optical pulse signal; attenuating and modulating the second optical pulse signal to obtain a quantum optical signal, and sending the quantum optical signal to the coupling unit; the frequency of pulses included in the first optical pulse signal is greater than the frequency of pulses included in the second optical pulse signal;

the coupling unit is configured to perform beam combination processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted, which includes the reference optical signal and the quantum optical signal, and transmit the transmission optical signal to a receiving device.

2. The transmission apparatus according to claim 1, wherein the coupling unit includes a polarization rotation unit connected to the first modulation unit, and a polarization coupling unit connected to both the polarization rotation unit and the second modulation unit;

the polarization rotation unit is configured to rotate the polarization state of the received reference optical signal by a first angle, and send the reference optical signal whose polarization state is rotated by the first angle to the polarization coupling unit;

the polarization coupling unit is used for performing polarization coupling processing on the received quantum optical signal pulse and the reference optical signal of which the polarization state rotates by the first angle to obtain a transmission optical signal to be transmitted, which is subjected to polarization multiplexing and time division multiplexing on the reference optical signal and the quantum optical signal, and transmitting the transmission optical signal to a receiving device;

or,

the coupling unit comprises a polarization rotation unit connected with the second modulation unit and a polarization coupling unit simultaneously connected with the polarization rotation unit and the first modulation unit;

the polarization rotation unit is configured to rotate the polarization state of the received quantum optical signal by a second angle, and send the quantum optical signal whose polarization state is rotated by the second angle to the polarization coupling unit;

the polarization coupling unit is configured to perform polarization coupling processing on the received reference optical signal pulse and the quantum optical signal whose polarization state rotates by the second angle to obtain a to-be-transmitted transmission optical signal that is polarization-multiplexed and time-division-multiplexed with the reference optical signal and the quantum optical signal, and send the transmission optical signal to a receiving device.

3. The transmitting apparatus according to claim 1 or 2, wherein the first modulation unit is further configured to:

classical information is modulated on the first optical pulse signal such that the classical information is included in the reference optical signal.

4. A receiving apparatus for quantum key distribution, comprising:

the coherent coupling unit is used for carrying out optical splitting processing on the received transmission optical signals comprising the reference optical signals and the quantum optical signals and carrying out coherent coupling on the transmission optical signals after the optical splitting processing according to the local oscillator optical signals to obtain first coherent coupled optical signals comprising the reference optical signals and second coherent coupled optical signals comprising the quantum optical signals; sending the first coherent coupled optical signal to a reference light balance detection unit, and sending the second coherent coupled optical signal to a quantum light balance detection unit; wherein an appearance frequency of a pulse of the reference optical signal included in the first coherently coupled optical signal is a first frequency, an appearance frequency of a pulse of the quantum optical signal included in the second coherently coupled optical signal is a second frequency, and the first frequency is greater than the second frequency;

the local oscillator unit is configured to generate the local oscillator optical signal and send the local oscillator optical signal to the coherent coupling unit;

the reference light balance detection unit is used for performing photoelectric conversion on the first coherent coupled optical signal, performing differential processing and amplification to obtain a first electric signal, and transmitting the first electric signal to the carrier recovery unit;

the quantum light balance detection unit is used for performing photoelectric conversion on the second coherent coupled optical signal, performing differential processing and amplification to obtain a second electric signal, and transmitting the second electric signal to the key recovery unit;

the carrier recovery unit is configured to determine phase frequency information between the local oscillator optical signal and the reference optical signal from the first electrical signal;

and the key recovery unit is used for recovering an original key from the second electric signal according to the received phase frequency information.

5. The receiving device of claim 4, wherein the bandwidth of the reference light balance detection unit is higher than the bandwidth of the quantum light balance detection unit;

and the gain of the reference light balance detection unit is lower than that of the quantum light balance detection unit.

6. The receiving apparatus according to claim 4 or 5, wherein the reference optical signal and the quantum optical signal included in the transmission optical signal are polarization-multiplexed;

the coherent coupling unit comprises a polarization light splitting unit, and a first sub-coherent coupling unit and a second sub-coherent coupling unit which are connected with the polarization light splitting unit, wherein the first sub-coherent coupling unit is connected with the reference light balance detection unit, and the second sub-coherent coupling unit is connected with the quantum light balance detection unit;

the local oscillator unit is configured to generate the local oscillator optical signal and divide the local oscillator optical signal into a first sub local oscillator optical signal and a second sub local oscillator optical signal; sending the first sub local oscillator optical signal to the first sub coherent coupling unit; sending the second sub local oscillator optical signal to the second sub coherent coupling unit;

the polarization beam splitting unit is configured to split the transmission optical signal into a first optical signal after optical splitting processing including the reference optical signal and a second optical signal after optical splitting processing including the quantum optical signal through polarization beam splitting processing;

the first sub coherent coupling unit is configured to perform coherent coupling on the first optical signal after optical division processing by using the first sub local oscillator optical signal, and output the first optical signal after coherent coupling;

and the second sub coherent coupling unit is configured to perform coherent coupling on the second optical split processed optical signal by using the second sub local oscillator optical signal, and output the second coherent coupled optical signal.

7. The receiving apparatus according to claim 6, wherein the local oscillation unit includes a local oscillation optical splitting unit, and a first local oscillation modulating unit and a second local oscillation modulating unit connected to the local oscillation optical splitting unit, and the first local oscillation modulating unit is connected to the first sub coherent coupling unit; the second local oscillator modulation unit is connected with the second sub-coherent coupling unit;

the local oscillator optical splitting unit is configured to split the generated local oscillator optical signal into a third sub local oscillator optical signal and a fourth sub local oscillator optical signal, send the third sub local oscillator optical signal to the first local oscillator modulation unit, and send the fourth sub local oscillator optical signal to the second local oscillator modulation unit; the polarization states of the third sub local oscillator optical signal and the first optical signal after optical splitting processing are consistent, and the polarization states of the fourth sub local oscillator optical signal and the second optical signal after optical splitting processing are consistent;

the first local oscillator modulation unit is used for carrying out chopping processing on the third sub local oscillator optical signal to obtain a first optical pulse local oscillator signal; performing phase modulation on the first optical pulse local oscillation signal to obtain a first sub local oscillation optical signal; the frequency of the pulse included in the first optical pulse local oscillation signal is a first frequency;

the second local oscillator modulation unit is configured to perform chopping processing on the fourth sub local oscillator optical signal to obtain a second optical pulse local oscillator signal; performing phase modulation on the second optical pulse local oscillation signal according to the phase frequency information to obtain a second sub local oscillation optical signal; and the frequency of the pulse included in the second optical pulse local oscillation signal is a second frequency.

8. The receiving apparatus as claimed in claim 7, wherein the first local oscillator modulation unit is further configured to:

delaying the first optical pulse local oscillation signal in a time domain, so that the obtained pulse in the first sub local oscillation optical signal corresponds to the pulse of the reference optical signal included in the first optical division processed optical signal in the time domain; so that the first local oscillation modulating unit performs phase modulation on the first optical pulse local oscillation signal delayed on the time domain;

the second local oscillation modulation unit is further configured to:

delaying the second optical pulse local oscillation signal in a time domain so that an obtained pulse in the second sub local oscillation optical signal corresponds to a pulse of a quantum optical signal included in the second optical division processed optical signal in the time domain; so that the second local oscillation modulating unit performs phase modulation on the second optical pulse local oscillation signal delayed in the time domain.

9. The receiving apparatus of claim 4 or 5, wherein the reference light balance detection unit is further configured to:

carrying out in-phase quadrature (IQ) detection on the first electric signal, and transmitting the IQ detected first electric signal to the carrier recovery unit;

the carrier recovery unit is further configured to:

classical information modulated on the reference optical signal is demodulated from the first electrical signal subjected to IQ detection.

10. A quantum key distribution method, comprising:

the sending device performs light splitting processing on the generated optical signal to obtain a first optical signal and a second optical signal;

the transmitting device performs chopping processing on the first optical signal to obtain a first optical pulse signal; attenuating and modulating the first optical pulse signal to obtain a reference optical signal;

the transmitting device performs chopping processing on the second optical signal to obtain a second optical pulse signal; attenuating and modulating the second optical pulse signal to obtain a quantum optical signal; the frequency of pulses included in the first optical pulse signal is greater than the frequency of pulses included in the second optical pulse signal;

the sending device performs beam combination processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted, which comprises the reference optical signal and the quantum optical signal, and transmits the transmission optical signal to a receiving device.

11. The method according to claim 10, wherein the sending apparatus performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted, which includes the reference optical signal and the quantum optical signal, and includes:

rotating the polarization state of the received reference optical signal by a first angle; carrying out polarization coupling processing on the received quantum optical signal pulse and the reference optical signal with the polarization state rotating by the first angle to obtain a transmission optical signal to be transmitted, wherein the transmission optical signal is obtained by polarization multiplexing and time division multiplexing of the reference optical signal and the quantum optical signal;

or,

rotating the polarization state of the received quantum optical signal by a second angle; and carrying out polarization coupling processing on the received reference optical signal pulse and the quantum optical signal with the polarization state rotating by the second angle to obtain a path of transmission optical signal to be transmitted, which is subjected to polarization multiplexing and time division multiplexing of the reference optical signal and the quantum optical signal.

12. The method according to claim 10 or 11, wherein before the sending apparatus performs beam combining processing on the reference optical signal and the quantum optical signal to obtain a transmission optical signal to be transmitted, the sending apparatus is further configured to:

classical information is modulated on the first optical pulse signal such that the classical information is included in the reference optical signal.

13. A quantum key distribution method, comprising:

the receiving device generates a local oscillator optical signal, performs optical splitting processing on a received transmission optical signal comprising a reference optical signal and a quantum optical signal, and performs coherent coupling on the transmission optical signal subjected to optical splitting processing according to the local oscillator optical signal to obtain a first coherent-coupled optical signal comprising the reference optical signal and a second coherent-coupled optical signal comprising the quantum optical signal; wherein an appearance frequency of a pulse of the reference optical signal included in the first coherently coupled optical signal is a first frequency, an appearance frequency of a pulse of the quantum optical signal included in the second coherently coupled optical signal is a second frequency, and the first frequency is greater than the second frequency;

the receiving device performs photoelectric conversion on the first coherent coupled optical signal, and performs differential processing and amplification to obtain a first electric signal; performing photoelectric conversion on the second coherent-coupled optical signal, and performing differential processing and amplification to obtain a second electrical signal;

the receiving device determines phase frequency information between the local oscillator optical signal and the reference optical signal from the first electrical signal; and recovering the original key from the second electric signal according to the phase frequency information.

14. The method of claim 13, wherein the reference optical signal and the quantum optical signal included in the transmitted optical signal are polarization multiplexed;

the receiving device generates a local oscillator optical signal, performs optical splitting processing on a received transmission optical signal including a reference optical signal and a quantum optical signal, and performs coherent coupling on the transmission optical signal subjected to the optical splitting processing according to the local oscillator optical signal to obtain a first coherent coupled optical signal including the reference optical signal and a second coherent coupled optical signal including the quantum optical signal, including:

the receiving device generates the local oscillator optical signal and divides the local oscillator optical signal into a first sub local oscillator optical signal and a second sub local oscillator optical signal;

the receiving device divides the transmission optical signal into a first optical division processed optical signal including the reference optical signal and a second optical division processed optical signal including the quantum optical signal through polarization optical division processing;

the receiving device performs coherent coupling on the first optical signal after optical splitting processing by using the first sub local oscillator optical signal, and outputs the first optical signal after coherent coupling; and performing coherent coupling on the second optical split processed optical signal by using the second sub local oscillator optical signal, and outputting the second coherent coupled optical signal.

15. The method of claim 14, wherein the receiving device generates the local optical signal and divides the local optical signal into a first sub local optical signal and a second sub local optical signal, including;

the receiving device divides the generated local oscillator optical signal into a third sub local oscillator optical signal and a fourth sub local oscillator optical signal; the polarization states of the third sub local oscillator optical signal and the first optical signal after optical splitting processing are consistent, and the polarization states of the fourth sub local oscillator optical signal and the second optical signal after optical splitting processing are consistent;

the receiving device performs chopping processing on the third sub local oscillator optical signal to obtain a first optical pulse local oscillator signal; performing phase modulation on the first optical pulse local oscillation signal to obtain a first sub local oscillation optical signal; the frequency of the pulse included in the first optical pulse local oscillation signal is a first frequency;

the receiving device performs chopping processing on the fourth sub local oscillation optical signal to obtain a second optical pulse local oscillation signal; performing phase modulation on the second optical pulse local oscillation signal according to the phase frequency information to obtain a second sub local oscillation optical signal; and the frequency of the pulse included in the second optical pulse local oscillation signal is a second frequency.

16. The method according to claim 15, wherein the receiving device performs a chopping process on the third sub local oscillator optical signal to obtain a first optical pulse local oscillator signal, and before performing a phase modulation on the first optical pulse local oscillator signal, further comprising:

delaying the first optical pulse local oscillation signal in a time domain, so that the obtained pulse in the first sub local oscillation optical signal corresponds to the pulse of the reference optical signal included in the first optical division processed optical signal in the time domain;

the receiving device performs chopping processing on the fourth sub local oscillator optical signal, after obtaining a second optical pulse local oscillator signal, and before performing phase modulation on the second optical pulse local oscillator signal, the method further includes:

delaying the second optical pulse local oscillation signal in the time domain, so that the obtained pulse in the second sub local oscillation optical signal corresponds to the pulse of the quantum optical signal included in the second optical division processed optical signal in the time domain.

17. The method as claimed in any one of claims 13 to 16, wherein said receiving means performs optical-to-electrical conversion on said first coherently coupled optical signal, and performs differential processing and amplification to obtain a first electrical signal, and further comprising:

and carrying out in-phase quadrature (IQ) detection on the first electric signal, and demodulating classical information modulated on the reference optical signal from the IQ detected first electric signal.

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