Method and device for improving performance of common-fiber quantum communication system

Abstract

The invention relates to the technical field of quantum communication, and provides a common-fiber quantum communication system performance improvement method and device. The method is applied to a common-fiber quantum communication system, two communication parties obtain screening keys through basis vector comparison and carry out an advantage extraction step after error rate estimation, and the advantage extraction step comprises the following steps: the two communication parties divide the screening keys into a group of every b bits; the sender selects a random bit c which belongs to {0, 1} to perform XOR operation with one group of screening keys XA = {x1, x2,..., xb} grouped by the sender, and an obtained result C is sent to the receiver; the receiver performs exclusive OR operation on the received C and a group of screening keys YA = {y1, y2,..., yb} corresponding to the XA position of the sender after grouping of the receiver to obtain a result C '; if C '= {0, 0,..., 0} or {1, 1,..., 1}, the receiver announces that the protocol succeeds, and the two communication parties reserve a first bit packet as an original key; otherwise, declaring that the protocol fails, and the two communication parties abandon all the b bits in the respective group.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication technology, and in particular to a method and device for improving the performance of a common-fiber quantum communication system. Background Art

[0002] Quantum key distribution (QKD) can establish information-theoretic secure key negotiation for both parties in long-distance communication. It has theoretically unconditional security, and even if the eavesdropper has infinite computing and storage capabilities, he still cannot obtain the key information. Although these QKDs can provide users with information-theoretic secure quantum communication, the actual QKD system usually has strict operating conditions and requires an independent fiber-optic communication channel. Specifically, in the actual QKD system, the transmitter needs to prepare a weak quantum signal of the order of single photons, and an independent fiber-optic channel needs to be set up in the experiment for the transmission of QKD quantum signals. However, for the large-scale deployment of QKD systems in existing optical fiber infrastructure, the application cost and the cost of transformation and upgrading are very huge, which makes the scalability and flexibility of the QKD system very low. Due to the limited optical fiber resources, the QKD quantum signal is transmitted in the same fiber as the classical optical communication system, which can effectively reduce the consumption of optical fiber resources by the quantum secure communication network and reduce the cost of network construction, which will promote the actual network deployment and large-scale application of quantum secure communication technology. The national communications industry standard "Technical Requirements for Quantum Key Distribution and Classical Optical Communication Co-fiber Transmission" stipulates the technical requirements for quantum key distribution and classical optical communication co-fiber transmission based on the BB84 protocol, including classification and application codes, models and reference points, parameter requirements, co-fiber transmission equipment technical requirements, network element management technical requirements, etc.

[0003] The widely used co-fiber transmission QKD technology in academia uses wavelength division multiplexing (WDM) to allow quantum and classical signals to coexist in the same optical fiber. WDM devices can multiplex optical signals of multiple wavelengths for common transmission in the same optical fiber channel, and can also separate optical signals of multiple different wavelengths from the shared optical fiber channel. The WDM-QKD system, which combines WDM technology with QKD technology, can effectively increase the number of channels that can be supported in the shared optical fiber channel, carry higher communication bandwidth, and effectively improve wavelength utilization. At present, WDM-QKD technology has been developed to be very mature, widely used in classical communication networks, and occupies an increasingly important position in the practical application of QKD systems. In the QKD system, a synchronized clock signal is required to ensure that the detector's door opening time is synchronized with the arrival time of the quantum signal pulse, thereby improving the detection efficiency. Many fiber-based QKD systems use WDM devices to merge clock signal light and quantum signal light into the same optical fiber to ensure the accuracy of clock synchronization. This is done because in the same optical fiber, the relative time drift of the clock synchronization light and the quantum signal light is smaller, so the timing is more stable, which is more conducive to the realization of high-speed quantum communication. Combining the idea of ​​​​merging quantum and clock channels with WDM technology and the scheme that has been implemented, the channels of classical optical communication and the quantum channels of the QKD system can be further transmitted in one optical fiber through wavelength division multiplexing. Using WDM devices, QKD and classical communication equipment are integrated in the same optical fiber channel, providing an effective solution for the large-scale deployment of QKD networks, making the QKD system have good flexibility and scalability in the existing optical fiber infrastructure. However, the wavelength division multiplexing scheme has an inherent defect. Classical optical communication will produce spontaneous Raman scattering in the optical fiber, generating noise photons that are the same as quantum light waves. These photons cannot be filtered out, which will cause the bit error rate of the QKD system to rise rapidly and the performance to deteriorate seriously. When experimental technical means cannot filter out noise light, it is necessary to find a protocol that can resist noise to improve the performance of the co-fiber QKD system. Summary of the invention

[0004] In view of the problem in the prior art that classical optical communication in a common-fiber quantum communication system will generate spontaneous Raman scattering in the optical fiber, causing a rapid increase in the system bit error rate and a serious degradation in performance, the present invention proposes a method and device for improving the performance of a common-fiber quantum communication system. By adding an advantage extraction step after the algorithm of the common-fiber QKD system, the transmission distance and key generation rate of the common-fiber quantum communication system can be increased, thereby improving the system performance.

[0005] In a first aspect, the present invention proposes a method for improving the performance of a co-fiber quantum communication system, comprising:

[0006] The communicating parties divide the screening key into groups of b bits each;

[0007] One of the sender's screening keys is X A ={x1,x2,…,x b}, the set of screening keys corresponding to the position of the receiver is Y A ={y1,y2,…,y b};

[0008] The sender selects a random bit c∈{0,1} and groups it with the sifting key X A ={x1,x2,…,x b} performs an XOR operation and sends the obtained result C to the receiver; the receiver combines the received C with the screening key Y after the receiver groups it A ={y1,y2,…,y b} Perform XOR operation to obtain the result C′;

[0009] If C′={0,0,…,0} or {1,1,…,1}, the receiver declares the protocol successful and the communicating parties retain the first packet as the original key; otherwise, the protocol is declared failed and the communicating parties discard all b bits in a group.

[0010] Furthermore, the security key rate after the advantage extraction step is:

[0011]

[0012] Among them, R represents the security key rate, b means that every b bits are divided into a group, q succ represents the success rate of the advantage extraction process, Q μ represents the signal state counting rate, Q1 represents the signal state single photon technology rate, and represents the corrected Bell state coefficient, H(x)=-xlogx-(1-x)log(1-x) is the binary Shannon entropy function, f represents the error correction efficiency, Indicates the signal state bit error rate.

[0013] Furthermore, the method is applied to a variety of quantum key distribution protocols, including the entrapped state BB84 quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, the reference frame-independent quantum key distribution protocol, and the dual-field quantum key distribution protocol.

[0014] In a second aspect, the present invention proposes a device for improving the performance of a common-fiber quantum communication system, comprising:

[0015] A screening key grouping module, used for the communicating parties to divide the screening keys into b groups;

[0016] The filter key XOR module is used for the sender to select a random bit c∈{0,1} and the filter key X after the sender is grouped A ={x1,x2,…,x b} performs an XOR operation and sends the obtained result C to the receiver; the receiver combines the received C with the screening key Y after the receiver groups it A ={y1,y2,…,y b} Perform XOR operation to obtain the result C′;

[0017] Determine the original key module, used to confirm that if C′={0,0,…,0} or {1,1,…,1}, the receiver declares the protocol successful, and the communicating parties retain the first bit group as the original key; otherwise, the protocol is declared failed, and the communicating parties discard all b bits in a group.

[0018] Furthermore, the security key rate after the advantage extraction step is:

[0019]

[0020] Among them, R represents the security key rate, b means that every b bits are divided into a group, q succ represents the success rate of the advantage extraction process, Q μ represents the signal state counting rate, Q1 represents the signal state single photon technology rate, and represents the corrected Bell state coefficient, H(x)=-xlogx-(1-x)log(1-x) is the binary Shannon entropy function, f represents the error correction efficiency, Indicates the signal state bit error rate.

[0021] Furthermore, the device is applied to a variety of quantum key distribution protocols, including the entrapped state BB84 quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, the reference frame-independent quantum key distribution protocol, and the dual-field quantum key distribution protocol.

[0022] The beneficial effects of the present invention are:

[0023] The performance improvement method of the common-fiber QKD system proposed in the present invention can improve the transmission distance of the common-fiber QKD system without changing the QKD system but only changing the post-processing process. It can be widely used in various QKD protocols with different encodings, such as the decoyed BB84 QKD protocol, the measurement device-independent QKD protocol, the reference frame-independent QKD protocol, and the dual-field QKD protocol. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the QKD protocol flow provided by an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of a QKD system and a wavelength division multiplexing scheme for classical optical communication provided by an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of the QKD protocol flow chart for advantage extraction provided by an embodiment of the present invention;

[0027] Figure 4 A schematic diagram of the process flow of advantage extraction provided by an embodiment of the present invention;

[0028] Figure 5 This is a diagram of the advantage extraction theory simulation results provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The main steps of the quantum key distribution (QKD) protocol include quantum process and classical process. The quantum process is divided into quantum state preparation, transmission and measurement, while the classical process is divided into basis, error correction and confidentiality amplification. The specific process is as follows: Figure 1 shown.

[0031] exist Figure 1 In the QKD protocol, after transmission through the quantum channel, the sender and receiver share the quantum state in Bell state coefficient λ i Satisfaction relationship and and They represent the single photon bit error rate in the X basis and Z basis respectively. According to the GLLP formula, the security key rate is

[0032]

[0033] Among them, Q μ represents the signal state count rate, Q1 is the signal state single photon count rate, and e1 is the signal state single photon bit error rate (when using Z-based coding and X-based bit error estimation, ), E μ is the signal state bit error rate, f is the error correction efficiency, and H(x)=-xlogx-(1-x)log(1-x) is the binary Shannon entropy function.

[0034] use Figure 1 As shown in the figure, the QKD system of the QKD process can work well in a dedicated optical fiber. However, in practical applications, the cost of laying out optical fibers for the QKD system is huge. Therefore, integrating the QKD system into the existing classical network through a wavelength division multiplexing scheme, so that quantum signals and classical signals are transmitted in the same optical fiber, has become a solution for the practical deployment of QKD. Wavelength division multiplexing methods such as Figure 2 As shown in the figure, the sender couples the classical data sent by the classical optical communication equipment, the synchronization signal sent by the QKD equipment and the quantum signal into the same optical fiber through the WDM device and transmits them simultaneously. After passing through the long-distance optical fiber, the receiver decodes these three signals through the wavelength division multiplexer. Since the quantum signal is weak and has a worse resistance to noise, a narrow bandwidth filter (NBF) is set at the quantum signal of the QKD receiving end to filter out the out-of-band noise.

[0035] However, the wavelength division multiplexing method has an inherent flaw. Classical optical communications will produce spontaneous Raman scattering in optical fibers, generating noise photons with the same wavelength as quantum light. These photons cannot be filtered out, causing the bit error rate of the QKD system to rise rapidly and performance to degrade severely. When experimental technical means cannot filter out the noise light, it is necessary to find a protocol that can resist noise to improve the performance of the co-fiber QKD system.

[0036] The technical problem to be solved by the present invention is to provide a method for improving the performance of a co-fiber QKD system, thereby solving the problem of short transmission distance caused by an increase in the bit error rate of the QKD system due to the generation of noise photons. The present invention solves the above technical problem through the following technical solutions:

[0037] Will Figure 2 The protocol used by the QKD system in the scheme ( Figure 1 ) is modified as shown below Figure 3 shown.

[0038] like Figure 4 As shown, a method for improving the performance of a common fiber quantum communication system provided by an embodiment of the present invention is applied to a common fiber quantum communication system. After the communicating parties obtain a screening key by comparing basis vectors and estimate the bit error rate, they perform an advantage extraction step, including:

[0039] S1: The communicating parties divide the screening key into groups of b bits each;

[0040] S2: The sender selects a random bit c∈{0,1} and one of the screening keys X after the sender groups it A ={x1,x2,…,x b} performs an XOR operation and sends the result C to the receiver; the receiver combines the received C with the X A The filter key Y at the corresponding position A ={y1,y2,…,y b} Perform XOR operation to obtain the result C′;

[0041] S3: If C′={0,0,…,0} or {1,1,…,1}, the receiver declares the protocol successful and both communicating parties retain one bit in the first group as the original key; otherwise, the protocol is declared a failure and both communicating parties discard all b bits in the corresponding group.

[0042] Furthermore, in order to prevent photon number splitting attacks, the b bits in a group should all be single photons.

[0043] In the advantage extraction QKD protocol, Alice and Bob share a quantum state before the advantage extraction process. The signal state bit error rate and the signal state single photon bit error rate are E μ and e1, the success rate of the advantage extraction process is In order to prevent photon number splitting attacks, b bits must be single photons to generate a secure key, with a success rate of

[0044] After advantage extraction, the quantum state shared by both parties is:

[0045]

[0046] in,

[0047]

[0048]

[0049] The signal state bit error rate is:

[0050]

[0051] According to the above analysis, the security key rate after the advantage extraction step is:

[0052]

[0053] Among them, R represents the security key rate, b means that every b bits are divided into a group, q succ represents the success rate of the advantage extraction process, Q μ represents the signal state counting rate, Q1 represents the signal state single photon technology rate, and represents the corrected Bell state coefficient, H(x)=-xlogx-(1-x)log(1-x) is the binary Shannon entropy function, f represents the error correction efficiency, Indicates the signal state bit error rate.

[0054] Furthermore, the method is applied to a variety of quantum key distribution protocols, including the entrapped state BB84 quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, the reference frame-independent quantum key distribution protocol, and the dual-field quantum key distribution protocol.

[0055] The embodiment of the present invention further provides a device for improving the performance of a common fiber quantum communication system, comprising:

[0056] A screening key grouping module, used for the communicating parties to divide the screening key into groups of b bits each;

[0057] The filter key XOR module is used for the sender to select a random bit c∈{0,1} and a set of filter keys X after the sender is grouped A ={x1,x2,…,x b} performs an XOR operation and sends the obtained result C to the receiving party; the receiving party groups the received C with the receiving party and then adds it to X A A set of sifting keys Y corresponding to the positions A ={y1,y2,…,y b} Perform XOR operation to obtain the result C′;

[0058] Determine the original key module, which is used to confirm that if C′={0,0,…,0} or {1,1,…,1}, the receiver declares the protocol successful, and the communicating parties retain the first bit in their respective groups as the original key; otherwise, the protocol is declared failed, and the communicating parties discard all b bits in a group.

[0059] Furthermore, the security key rate after the advantage extraction step is:

[0060]

[0061] Among them, R represents the security key rate, b means that every b bits are divided into a group, q succ represents the success rate of the advantage extraction process, Q μ represents the signal state counting rate, Q1 represents the signal state single photon technology rate, and represents the corrected Bell state coefficient, H(x)=-xlogx-(1-x)log(1-x) is the binary Shannon entropy function, f represents the error correction efficiency, Indicates the signal state bit error rate.

[0062] Furthermore, the device is applied to a variety of quantum key distribution protocols, including the entrapped state BB84 quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, the reference frame-independent quantum key distribution protocol, and the dual-field quantum key distribution protocol.

[0063] like Figure 5 As shown, the theoretical simulation results show that in the decoyed state QKD co-fiber system, at 8.6dBm classical optical transmission power, the use of advantage extraction (AD) technology can increase the transmission distance of QKD from 25.9km to 153.4km, and the transmission distance is increased by 4.9 times, thus greatly improving the performance of co-fiber QKD.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the performance of a co-fiber quantum communication system, characterized in that: Applied to the co-fiber quantum communication system, after the communicating parties obtain the screening key through basis vector comparison and pass the bit error rate estimation, they perform the advantage extraction step, which includes: The communicating parties divide the screening key into groups of b bits each; One of the screening keys of the sender is X A ={x1,x2,…,x b }, the set of screening keys corresponding to the position of the receiver is Y A ={y1,y2,…,y b }; The sender selects a random bit c∈{0,1} and groups it with the sifting key X A ={x1,x2,…,x b } performs an XOR operation and sends the obtained result C to the receiver; the receiver combines the received C with the screening key Y after the receiver groups it A ={y1,y2,…,y b } Perform XOR operation to obtain the result C′; If C′={0,0,…,0} or {1,1,…,1}, the receiver declares the protocol successful and both communicating parties retain the first bit group as the original key; otherwise, the protocol is declared failed and both communicating parties discard all b bits in a group.

2. A method for improving the performance of a co-fiber quantum communication system according to claim 1, characterized in that: The security key rate after the advantage extraction step is: Among them, R represents the security key rate, b means that every b bits are divided into a group, q succ represents the success rate of the advantage extraction process, Q μ represents the signal state counting rate, Q1 represents the signal state single photon technology rate, and represents the corrected Bell state coefficient, H(x)=-xlogx-(1-x)log(1-x) is the binary Shannon entropy function, f represents the error correction efficiency, Indicates the signal state bit error rate.

3. A method for improving the performance of a co-fiber quantum communication system according to claim 1, characterized in that: This method is applied to a variety of quantum key distribution protocols, including the entrapped BB84 quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, the reference frame-independent quantum key distribution protocol, and the dual-field quantum key distribution protocol.

4. A device for improving the performance of a common fiber quantum communication system, characterized in that: Applied to the co-fiber quantum communication system, after the communicating parties obtain the screening key through basis vector comparison and pass the bit error rate estimation, they perform the advantage extraction step, which includes: A screening key grouping module, used for the communicating parties to divide the screening key into groups of b bits each; The filter key XOR module is used for the sender to select a random bit c∈{0,1} and a set of filter keys X after the sender is grouped A ={x1,x2,…,x b } performs an XOR operation and sends the obtained result C to the receiving party; the receiving party compares the received C with the corresponding X after the receiving party groups it A Filter key for position Y A ={y1,y2,…,y b } Perform XOR operation to obtain the result C′; Determine the original key module, used to confirm that if C′={0,0,…,0} or {1,1,…,1}, the receiver declares the protocol successful, and the communicating parties retain the first bit group as the original key; otherwise, the protocol is declared failed, and the communicating parties discard all b bits in a group.

5. The device for improving the performance of a common fiber quantum communication system according to claim 4, characterized in that: The security key rate after the advantage extraction step is: Among them, R represents the security key rate, b means that every b bits are divided into a group, q succ represents the success rate of the advantage extraction process, Q μ represents the signal state counting rate, Q1 represents the signal state single photon technology rate, and represents the corrected Bell state coefficient, H(x)=-xlogx-(1-x)log(1-x) is the binary Shannon entropy function, f represents the error correction efficiency, Indicates the signal state bit error rate.

6. The device for improving the performance of a common fiber quantum communication system according to claim 4, characterized in that: The device is used in a variety of quantum key distribution protocols, including the entrapped BB84 quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, the reference frame-independent quantum key distribution protocol and the dual-field quantum key distribution protocol.

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