Quantum key distribution multi-step advantage extraction method and device

Abstract

This invention discloses a multi-step advantage extraction method and apparatus for quantum key distribution. The method includes: Step 1, selecting an advantage extraction parameter b; Step 2, decomposing the advantage extraction parameter b: b = b1 × b2 × … × b k Step 3: Perform k operations on the bit sequence, with lengths b1, b2, ..., b... k This invention provides a single-step advantage extraction method to obtain the final key bits. The device includes: an advantage extraction parameter selection module; an advantage extraction parameter decomposition module; and a multi-step advantage extraction module. This invention can reduce bit sequence loss before error correction and improve the key rate, transmission distance, and error tolerance of different encoded quantum key distribution systems, thereby enhancing the robustness of practical quantum key distribution systems.

Description

Technical Field

[0001] This invention relates to the field of quantum key distribution technology, and in particular to a method and apparatus for multi-step advantage extraction in quantum key distribution. Background Technology

[0002] Quantum Key Distribution (QKD) is a novel technology for improving key security. Its security mechanism is based on the quantum uncertainty principle and the no-cloning principle, meaning that no attacker can obtain the key generated by legitimate parties through eavesdropping. This conclusion has been rigorously proven in theory. The quantum key distribution protocol was proposed in 1984 by Brassard and Bennett [CH Bennett and G. Brassard, Proceedings of IEEE International Conference on Computers, Systems and Signal Processing, Bangalore, India. New York: IEEE, 175-179 (1984).]. It can establish information-theoretic-secure keys for long-distance communication between two parties. The security of quantum key distribution is guaranteed by the fundamental principles of quantum mechanics; even if a third-party eavesdropper possesses infinite computing and storage capabilities, they cannot obtain the key information. The main steps of the quantum key distribution protocol include quantum processes and classical processes. The quantum processes are divided into quantum state preparation, transmission, and measurement, while the classical processes are divided into basis setting, error correction, and secure amplification. The flow of the quantum key distribution protocol is as follows: Figure 1 As shown.

[0003] Due to the non-ideal nature of practical devices or interference from eavesdroppers in the channel, real-world quantum key distribution systems will have a certain bit error rate. The magnitude of the bit error rate directly affects the key rate and key transmission distance of the practical quantum key distribution system. Therefore, how to improve the key rate of a quantum key distribution system given a certain bit error rate is a difficult problem that needs to be solved in the practical application of quantum key distribution.

[0004] To improve the maximum error tolerance of quantum key distribution systems, Chau [HFChau, Phys.Rev.A 66, 060302 (2002)] increased the maximum error tolerance of the BB84 quantum key distribution protocol from 11% to 20% by XORing the original data. Maurer [U.Maurer, IEEE Trans.Inf.Theory 39, 733 (1993)] was the first in classical cryptography to propose that the security of classical cryptographic protocols could be improved by advantage extraction techniques. Subsequently, Renner [R.Renner. International Journal of Quantum Information, (2008)] proposed that the security of the BB84 quantum key distribution protocol and the six-state quantum key distribution protocol could be analyzed using advantage extraction techniques, and combined with random noise addition techniques, the error tolerance was improved. Meanwhile, Tan et al. [EY-Z.Tan, CC-W.Lim, R.Renner, Phys.Rev.Lett.124,020502(2020).] applied the advantage extraction technique to a device-independent quantum key distribution protocol, increasing the maximum error tolerance from 7.1% to 9.1%. Li et al. [HWLi,CMZhang,MSJiang,&Q.Y.Cai, Communications Physics,5,53,(2022).] subsequently applied the advantage extraction technique to a practical quantum key distribution system, analyzing the improvement in error tolerance and key distance in decoy-state BB84 quantum key distribution systems, six-state quantum key distribution systems, and MDI-quantum key distribution systems. They demonstrated that the practical advantage extraction method only requires post-selection of the original measurement data, can be applied to quantum key distribution systems with various protocols and encodings, significantly improving the error tolerance, key rate, and transmission distance of quantum key distribution systems, and is a universally applicable security enhancement method.

[0005] In the advantage extraction technique, both the sender and receiver perform preprocessing on the bit sequence before error correction to extract data that is more advantageous to both parties. Specifically, in this technique, both Alice (sender) and Bob (receiver) divide their bit sequence into bit blocks of length x1,…,x... b and y1,…,y b b is the length of the advantage extraction. Alice selects a random number c∈{0,1}, and Alice compares c with x1,…,x b The results of the XOR operation are denoted as d1, ..., d b Alice will use d1,…,d bThe data is sent to Bob via a public channel. Bob then compares the received data with y1, ...,y... b XOR results If Bob receives a sequence of all 0s:0,…,0 or all 1s:1,…,1, then Alice and Bob both save the first bits x1 and y1 of their bit blocks; otherwise, they discard the bits and report an error. Combining the advantage extraction technique, the quantum key distribution protocol flow is as follows: Figure 2 As shown.

[0006] When the value of b is large, single-step advantage extraction suffers from significant bit sequence loss before error correction. If b bits are error-free, b-1 bits need to be discarded; if there are one to b-1 error bits, all b bits need to be discarded. This advantage extraction method results in substantial loss of the bit sequence generated by quantum key distribution. Summary of the Invention

[0007] This invention addresses the problem of significant bit sequence loss caused by single-step advantage extraction in quantum key distribution. It proposes a multi-step advantage extraction method and apparatus for quantum key distribution, which can reduce bit sequence loss before error correction and improve the key rate, transmission distance, and error tolerance of different encoded quantum key distribution systems. This enhances the robustness of practical quantum key distribution systems and demonstrates the practicality of quantum key distribution equipment in industrialization and commercialization.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention proposes a multi-step advantage extraction method for quantum key distribution, comprising:

[0010] Step 1, select the advantage extraction parameter b;

[0011] Step 2, decompose the advantage extraction parameter b: b = b1 × b2 × … × b k ;

[0012] Step 3: Perform k operations on the bit sequence, with lengths b1, b2, ..., b... k The single-step advantage is used to extract and obtain the final key bits.

[0013] Further, step 3 includes:

[0014] Step 3.1: Divide the bit sequence into groups of b1 bits and extract the advantage of each group;

[0015] Step 3.2: Divide the retained bit sequence into b2-bit groups and extract the advantage of each group;

[0016] Step 3.3: Perform advantage extraction as described in Steps 3.1 and 3.2 until each bit of the retained bit sequence is optimized. k The bits are divided into groups, and the advantages of each group are extracted to obtain the final key bits.

[0017] Furthermore, this multi-step advantage extraction method can be applied to various quantum key distribution protocols, including the BB84 quantum key distribution protocol, the six-state quantum key distribution protocol, the continuous variable quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, and the device-independent quantum key distribution protocol.

[0018] Furthermore, this multi-step advantage extraction method can be combined with decoy state schemes and applied to quantum key distribution systems with various encoding methods, including polarization-coded quantum key distribution systems, phase-coded quantum key distribution systems, and time-phase-coded quantum key distribution systems.

[0019] Another aspect of the present invention proposes a multi-step advantage extraction device for quantum key distribution, comprising:

[0020] The advantage extraction parameter selection module is used to select the advantage extraction parameter b;

[0021] The advantage extraction parameter decomposition module is used to decompose the advantage extraction parameter b: b = b1 × b2 × … × b k ;

[0022] The multi-step advantage extraction module is used to sequentially process the bit sequence k times with lengths b1, b2, ..., b k The single-step advantage is used to extract and obtain the final key bits.

[0023] Furthermore, the multi-step advantage extraction module is specifically used for:

[0024] Step 3.1: Divide the bit sequence into groups of b1 bits and extract the advantage of each group;

[0025] Step 3.2: Divide the retained bit sequence into b2-bit groups and extract the advantage of each group;

[0026] Step 3.3: Perform advantage extraction as described in Steps 3.1 and 3.2 until each bit of the retained bit sequence is optimized. k The bits are divided into groups, and the advantages of each group are extracted to obtain the final key bits.

[0027] Furthermore, this multi-step advantage extraction device can be applied to various quantum key distribution protocols, including the BB84 quantum key distribution protocol, the six-state quantum key distribution protocol, the continuous variable quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, and the device-independent quantum key distribution protocol.

[0028] Furthermore, this multi-step advantage extraction device can be combined with decoy state schemes and applied to quantum key distribution systems with various encoding methods, including polarization-encoded quantum key distribution systems, phase-encoded quantum key distribution systems, and time-phase-encoded quantum key distribution systems.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The multi-step advantage extraction method and apparatus for quantum key distribution proposed in this invention only requires post-selection of the original measurement data, without requiring modification of the quantum state preparation, modulation, and measurement devices. It can be applied to various quantum key distribution protocols such as BB84 quantum key distribution protocol, six-state quantum key distribution protocol, continuous variable quantum key distribution protocol, measurement device-independent quantum key distribution protocol, and device-independent quantum key distribution protocol. At the same time, this invention can be combined with decoy state schemes and applied to quantum key distribution systems with various encoding methods, including polarization-encoded quantum key distribution systems, phase-encoded quantum key distribution systems, and time-phase-encoded quantum key distribution systems.

[0031] The multi-step advantage extraction method and apparatus for quantum key distribution proposed in this invention can reduce the loss of bit sequences before error correction, and at the same time improve the key rate, transmission distance and error tolerance of different encoded quantum key distribution systems, thereby improving the robustness of practical quantum key distribution systems. Attached Figure Description

[0032] Figure 1 A flowchart of a quantum key distribution protocol;

[0033] Figure 2 A flowchart of a quantum key distribution protocol for single-step advantage extraction;

[0034] Figure 3 Flowchart of a single-step advantage extraction method for quantum key distribution;

[0035] Figure 4 Flowchart of a multi-step advantage extraction method for quantum key distribution;

[0036] Figure 5 A flowchart of a multi-step advantage extraction quantum key distribution protocol;

[0037] Figure 6 This is a schematic diagram of the multi-step advantage extraction device architecture for quantum key distribution according to an embodiment of the present invention. Detailed Implementation

[0038] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments:

[0039] The present invention provides a multi-step advantage extraction method for quantum key distribution, comprising:

[0040] S1, Select the advantageous extraction parameter b;

[0041] S2, decompose the advantage extraction parameter b into b = b1 × b2 × … × b k ;

[0042] S3, sequentially process the bit sequence k times with lengths b1, b2, ..., b k The single-step advantage is used to extract and obtain the final key bits.

[0043] Furthermore, S3 includes:

[0044] S31, divide the bit sequence into groups of b1 bits, and extract the advantage of each group;

[0045] S32, the retained bit sequence is divided into groups of b2 bits, and the advantage is extracted from each group;

[0046] S33, perform advantage extraction according to the methods of S31 and S32 until each bit of the retained bit sequence is optimized. k The bits are divided into groups, and the advantages of each group are extracted to obtain the final key bits.

[0047] Furthermore, this multi-step advantage extraction method can be applied to various quantum key distribution protocols, including the BB84 quantum key distribution protocol, the six-state quantum key distribution protocol, the continuous variable quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, and the device-independent quantum key distribution protocol.

[0048] Furthermore, this multi-step advantage extraction method can be combined with decoy state schemes and applied to quantum key distribution systems with various encoding methods, including polarization-coded quantum key distribution systems, phase-coded quantum key distribution systems, and time-phase-coded quantum key distribution systems.

[0049] To describe in detail the specific steps of multi-step advantage extraction, we first give the steps of single-step advantage extraction as follows: Figure 3 As shown.

[0050] The above single-step advantage extraction process extracts advantages from b bits. If there is an erroneous bit, all b bits need to be discarded, which results in significant waste of the bit sequence. Unlike single-step advantage extraction, this invention proposes a multi-step advantage extraction scheme, as detailed below. Figure 4 As shown.

[0051] In the multi-step advantage extraction scheme, the b bits are divided into shorter groups, and advantage extraction is performed on each shorter group separately. Based on the multi-step advantage extraction technique, the quantum key distribution protocol flow is as follows: Figure 5 As shown.

[0052] Let's illustrate this with an example: Suppose Alice has the following 18 bits.

[0053] x1, x2, x3, x4, x5, x6, x7, x8, x9, x 10 x 11 x 12 x 13 x 14 x 15 x 16 x 17 x 18

[0054] Assume Bob has the following 18 bits.

[0055] y1, y2, y3, y4, y5, y6, y7, y8, y9, y 10 y 11 y 12 y 13 y 14 y 15 y 16 y 17 y 18

[0056] When there is a 1-bit error in 18 bits, let's assume x1 ≠ y1. When performing single-step advantage extraction on 18 bits, the single-step advantage extraction scheme needs to discard all 18 bits.

[0057] The multi-step advantage extraction scheme can be divided into 9 groups with b1=2. Because a short grouping method is used, only the first group (x1, x2) is inconsistent with y1, y2. Therefore, both sides need to discard the first group, and the remaining bit sequence is:

[0058] The bit sequence at Alice's end

[0059] x3,x5,x7,x9,x 11 ,x 13 ,x 15 ,x 17

[0060] Bit sequence at Bob end

[0061] y3,y5,y7,y9,y 11 ,y 13 ,y 15 ,y17

[0062] For these 8 bits, Alice and Bob can continue with the b2=2 advantage extraction scheme, and the remaining bit sequence is:

[0063] The bit sequence at Alice's end

[0064] x3,x7,x 11 ,x 15

[0065] Bit sequence at Bob end

[0066] y3,y7,y 11 ,y 15

[0067] For these 4 bits, Alice and Bob can continue with the b3=2 advantage extraction scheme, and the remaining bit sequence is:

[0068] The bit sequence at Alice's end

[0069] x3,x 11

[0070] Bit sequence at Bob end

[0071] y3,y 11

[0072] For these two bits, Alice and Bob can continue with the b4=2 advantage extraction scheme, and the remaining bit sequence is:

[0073] Bits at Alice's end

[0074] x3

[0075] Bits at the Bob end

[0076] y3

[0077] Through the above four steps of advantage extraction, Alice and Bob can obtain the advantage-extracted bits x3 and y3.

[0078] The following analysis further examines the improvement in key rate resulting from multi-step advantage extraction. Assume the protocol performs k steps with lengths b1, b2, ..., b k The advantages of quantum key distribution (QKD) can be extracted. The bit error rate of QKD is e. The Bell state coefficients used in QKD security analysis are λ1, λ2, λ3, and λ4, which are directly related to the bit error rates of the two sets of basis vectors in the QKD protocol. We will now analyze this in detail.

[0079] The success rate of the first advantage extraction of length b1 is The bit error rate changed after the first advantage extraction, becoming The Bell state coefficients after advantage extraction are corrected to

[0080]

[0081]

[0082]

[0083]

[0084] Second advantage extraction of length b2: success rate The bit error rate changed after the second advantage extraction, becoming The Bell state coefficients after advantage extraction are corrected to

[0085]

[0086]

[0087]

[0088]

[0089] And so on, the length of the kth iteration is b. k Advantages: Success Rate After the k-th advantage extraction, the bit error rate changed to... The Bell state coefficients after advantage extraction are corrected to

[0090]

[0091]

[0092]

[0093]

[0094] Based on the above analysis, the final key rate after k rounds of advantage extraction can be given.

[0095]

[0096] By comparing calculations, it can be found that the key rate formula for multi-step advantage extraction is better than that for single-step advantage extraction.

[0097] Based on the above embodiments, such as Figure 6 As shown, the present invention also proposes a multi-step advantage extraction device for quantum key distribution, comprising:

[0098] The advantage extraction parameter selection module is used to select the advantage extraction parameter b;

[0099] The advantage extraction parameter decomposition module is used to decompose the advantage extraction parameter b: b = b1 × b2 × … × b k ;

[0100] The multi-step advantage extraction module is used to sequentially process the bit sequence k times with lengths b1, b2, ..., b k The single-step advantage is used to extract and obtain the final key bits.

[0101] Furthermore, the multi-step advantage extraction module is specifically used for:

[0102] Step 3.1: Divide the bit sequence into groups of b1 bits and extract the advantage of each group;

[0103] Step 3.2: Divide the retained bit sequence into b2-bit groups and extract the advantage of each group;

[0104] Step 3.3: Perform advantage extraction as described in Steps 3.1 and 3.2 until each bit of the retained bit sequence is optimized. k The bits are divided into groups, and the advantages of each group are extracted to obtain the final key bits.

[0105] Furthermore, this multi-step advantage extraction device can be applied to various quantum key distribution protocols, including the BB84 quantum key distribution protocol, the six-state quantum key distribution protocol, the continuous variable quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, and the device-independent quantum key distribution protocol.

[0106] Furthermore, this multi-step advantage extraction device can be combined with decoy state schemes and applied to quantum key distribution systems with various encoding methods, including polarization-encoded quantum key distribution systems, phase-encoded quantum key distribution systems, and time-phase-encoded quantum key distribution systems.

[0107] In summary, the multi-step advantage extraction method and apparatus for quantum key distribution proposed in this invention only requires post-selection of the original measurement data, without requiring modification to the quantum state preparation, modulation, and measurement devices. It can be applied to various quantum key distribution protocols, including BB84, six-state, continuous-variable, measurement-device-independent, and device-independent protocols. Furthermore, this invention can be combined with decoy state schemes for quantum key distribution systems with various encoding methods, including polarization-encoded, phase-encoded, and time-phase-encoded quantum key distribution systems. This invention can reduce bit sequence loss before error correction and improve the key rate, transmission distance, and error tolerance of different encoded quantum key distribution systems, thereby enhancing the robustness of practical quantum key distribution systems.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multi-step advantage extraction method for quantum key distribution, characterized in that, include: Step 1, Select Advantage Extraction Parameters , The length of the advantage extraction; Step 2, extract parameters for advantages Decompose: , This represents the total number of times the advantage was extracted; Step 3, process the bit sequence sequentially. Secondary dominance extraction, the group lengths for dominance extraction are respectively After each advantage extraction, the first bit of each group is retained. All bits retained from the previous advantage extraction are concatenated in their original order and used as input for the next advantage extraction. The final key bits are obtained after the second advantage extraction.

2. The multi-step advantage extraction method for quantum key distribution according to claim 1, characterized in that, Step 3 includes: Step 3.1: For each bit sequence Divide the bits into groups, extract the advantage of each group, and retain the first bit of each group; Step 3.2: Concatenate all the bits retained in Step 3.1 in their original order, and process each bit in the concatenated bit sequence... Divide the bits into groups, extract the advantage of each group, and retain the first bit of each group; Step 3.3: Repeat the grouping-advantage extraction-retention operation, sequentially processing the bit sequence concatenated after each retention according to the group length. Perform advantage extraction until each of the remaining bit sequences is optimized. The bits are divided into groups, and the advantage of each group is extracted. The first bit of each group is retained to obtain the final key bits.

3. The multi-step advantage extraction method for quantum key distribution according to claim 1, characterized in that, This multi-step advantage extraction method has been applied to various quantum key distribution protocols, including the BB84 quantum key distribution protocol, the six-state quantum key distribution protocol, the continuous variable quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, and the device-independent quantum key distribution protocol.

4. The multi-step advantage extraction method for quantum key distribution according to claim 1, characterized in that, This multi-step advantage extraction method, combined with the decoy state scheme, is applied to quantum key distribution systems with various encoding methods, including polarization-encoded quantum key distribution systems, phase-encoded quantum key distribution systems, and time-phase-encoded quantum key distribution systems.

5. A multi-step advantage extraction device for quantum key distribution, characterized in that, include: The advantage extraction parameter selection module is used to select advantage extraction parameters. , The length of the advantage extraction; The advantage extraction parameter decomposition module is used to decompose the advantage extraction parameters. Decompose: , This represents the total number of times the advantage was extracted; The multi-step advantage extraction module is used to sequentially process the bit sequence. Secondary dominance extraction, the group lengths for dominance extraction are respectively After each advantage extraction, the first bit of each group is retained. All bits retained from the previous advantage extraction are concatenated in their original order and used as input for the next advantage extraction. The final key bits are obtained after the second advantage extraction.

6. The quantum key distribution multi-step advantage extraction device according to claim 5, characterized in that, The multi-step advantage extraction module is specifically used for: Step 3.1: For each bit sequence Divide the bits into groups, extract the advantage of each group, and retain the first bit of each group; Step 3.2: Concatenate all the bits retained in Step 3.1 in their original order, and process each bit in the concatenated bit sequence... Divide the bits into groups, extract the advantage of each group, and retain the first bit of each group; Step 3.3: Repeat the grouping-advantage extraction-retention operation, sequentially processing the bit sequence concatenated after each retention according to the group length. Perform advantage extraction until each of the remaining bit sequences is optimized. The bits are divided into groups, and the advantage of each group is extracted. The first bit of each group is retained to obtain the final key bits.

7. The quantum key distribution multi-step advantage extraction device according to claim 5, characterized in that, This multi-step advantage extraction device is applied to various quantum key distribution protocols, including the BB84 quantum key distribution protocol, the six-state quantum key distribution protocol, the continuous variable quantum key distribution protocol, the measurement device-independent quantum key distribution protocol, and the device-independent quantum key distribution protocol.

8. The quantum key distribution multi-step advantage extraction device according to claim 5, characterized in that, This multi-step advantage extraction device, combined with a decoy state scheme, is applied to quantum key distribution systems with various encoding methods, including polarization-encoded quantum key distribution systems, phase-encoded quantum key distribution systems, and time-phase-encoded quantum key distribution systems.

Images