A quantum secure direct communication method and system based on a passive decoy state

Abstract

The application discloses a quantum secure direct communication method and system based on passive decoy state, wherein an information receiver uses two phase random coherent pulses, the two coherent pulses are interfered and attenuated through a beam splitter to generate a weak coherent pulse light beam with random intensity; the information receiver further randomly encodes the weak coherent pulse and sends the same to an information sender; the information sender sends the photon pulse back to the information receiver after information encoding; and the information receiver decodes the information sent by the information sender according to the initial pulse information sent by the information receiver. The method does not need to actively modulate the intensity of a light source, can realize passive decoy state, can be realized by using linear optical devices, simplifies experimental operation, can resist side channel attacks of a light source modulator by a third-party eavesdropper and can enhance the security of quantum secure direct communication.

Description

Technical Field

[0001] This invention belongs to the field of quantum communication, specifically relating to a quantum-secure direct communication method and system based on a passive decoy state. Background Technology

[0002] Quantum-secure direct communication (QSDC) is an important branch of quantum communication. It can securely transmit information directly between communicating parties. In 2000, Long Guilu et al. proposed the first quantum-secure direct communication protocol. In 2003, Deng Fuguo et al. proposed a two-step QSDC scheme based on EPR entangled pairs using the idea of ​​dense coding; in 2004, the research group proposed a one-time pad QSDC scheme based on single photons; the one-time pad QSDC scheme based on single photons and the two-step QSDC scheme based on entanglement were experimentally verified in 2016 and 2017, respectively. However, in practical applications, devices are not perfect. These flawed devices may provide opportunities for third-party eavesdroppers, threatening the security of the protocol. In 2020, Pan Dong et al. analyzed the secure information capacity of the QSDC protocol with weak-term dry pulse light sources, considering collective attacks and photon number splitting attacks. They used the decoy state method for parameter estimation. However, imperfections in the light source result in pulses containing vacuum states and multiphoton components. When actively modulating the light source intensity using decoy state methods, security vulnerabilities can be introduced, allowing third-party eavesdroppers to launch Trojan horse attacks to steal information. In 2009, Curty et al. proposed a passive decoy state method. Using two coherent beams with random phases, decoy states can be passively prepared without additional active modulation operations, simplifying experimental setup and eliminating side-channel information leakage caused by active operations. Currently, the passive decoy state method using coherent light has not been applied to QSDC. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a quantum-secure direct communication method and system based on passive decoy states, which can simplify experimental operations, resist side-channel attacks against light source modulators, and improve communication security.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0005] A quantum-secure direct communication method based on a passive decoy state includes the following steps:

[0006] Step 1: The information receiver prepares two coherent pulses with intensity μ and random phase. Pulses μ1 and μ2 are interfered by a beam splitter to generate pulse μ. 1+2 μ 1-2 , measuring μ 1-2 Obtain μ 1+2The intensity information is used to classify photon pulses into three categories based on their intensity. Then, the pulse μ... 1-2 The input is fed into the encoder, where it is randomly encoded, and the output is μ. out .

[0007] Step 2: The information receiver repeats Step 1 to generate a series of photon pulse sequences and sends them to the information sender.

[0008] Step 3: The sender stores the received photon pulse sequence. Then, the receiver and sender, after consultation, select a subset of photon pulses for the first round of security testing. The receiver publishes the encoding and intensity information of the photon pulses at the corresponding positions. The sender categorizes the measurement results of the photon pulses into three classes based on the receiver's intensity information and estimates the bit error rate using a decoy state method. If the bit error rate exceeds a pre-set threshold, the security test fails, and communication terminates. If the bit error rate is below the threshold, communication continues.

[0009] Step 4: The information sender randomly selects a portion of the remaining signal-state photon pulses for random encoding, and encodes the remaining signal-state photon pulses for information encoding. After encoding, the information is sent to the information receiver.

[0010] Step 5: The information receiver performs X-basis or Z-basis measurements on the received photon pulses based on its own random coding information.

[0011] Step 6: The sender publishes the location and random coding information of the randomly coded photon pulse. The receiver compares the measurement results at the corresponding location to estimate the bit error rate. If the bit error rate is higher than a pre-set threshold, the security check fails and communication is terminated. If the bit error rate is lower than the threshold, communication continues.

[0012] Step 7: The information receiver reconstructs the information sender's information through classical post-processing based on the measurement information of photon pulses at other locations.

[0013] A quantum-safe direct communication system, comprising an information sender and an information receiver, for executing the quantum-safe direct communication method based on a passive decoy state according to the present invention.

[0014] The present invention has the following beneficial effects:

[0015] (1) The quantum secure direct communication method based on passive decoy state proposed in this invention uses the decoy state method, which can resist photon number splitting attack and coherent attack, improve the security capacity of quantum secure direct communication, and improve the communication distance and security information capacity.

[0016] (2) The quantum secure direct communication method based on passive decoy state proposed in this invention can passively modulate the strength of the decoy state without additional active modulation, and can resist side-channel attacks against the light source modulator, thereby improving the security of quantum secure direct communication.

[0017] (2) The quantum secure direct communication method based on passive decoy state proposed in this invention uses linear optical devices, which is beneficial for practical applications. Attached Figure Description

[0018] Figure 1 This is a flowchart of the quantum-secure direct communication method provided in the embodiments of the present invention;

[0019] Figure 2 This is a structural principle block diagram of a quantum-secure direct communication system provided in an embodiment of the present invention;

[0020] Figure 3 This is a structural diagram of a passive deception state provided in an embodiment of the present invention;

[0021] Figure 4 This diagram illustrates the relationship between the secure information capacity and channel loss of the quantum-secure direct communication method provided in this invention under different intensities. The x-axis represents channel loss, and the y-axis represents secure information capacity. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0023] Example 1:

[0024] As attached Figure 1 As shown in the figure, this embodiment of a quantum-secure direct communication method based on a passive decoy state includes the following steps.

[0025] Step 1: As Figure 3 As shown, Bob, the information receiver, prepares two coherent pulses with intensity μ and random phase. The coherent pulses μ1 and μ2 are interfered by a beam splitter (BS) to generate pulse μ. 1+2 μ 1-2 , measuring μ 1-2 Obtain μ 1+2 The intensity information is used to classify photon pulses into three categories based on their intensity. Then, the pulse μ... 1-2 The input is fed into the encoder, where it is randomly encoded, and the output state μ is obtained. out .

[0026] Two coherent pulses with intensity μ and random phase are described as follows:

[0027]

[0028] Where μ represents the intensity of the coherent pulse; e is the natural constant; φ1 and φ2 represent the random phase of the coherent pulse; and j is an imaginary number. 2 =-1.

[0029] The pulse μ1 is generated by interfering pulses μ1 and μ2 through a beam splitter. 1+2 μ 1-2 The expression is as follows:

[0030]

[0031] Where t is the transmittance of the beam splitter, and t << 1.

[0032] Then, the coherent pulse μ 1-2 The input is fed into the encoder, where it undergoes random encoding, and the output is μ. out The expression is as follows:

[0033]

[0034] Where I is the output state μ out The strength,

[0035] I = 2μt(cos 2 θ),

[0036]

[0037]

[0038] in This represents the quantum state of a randomly encoded photon.

[0039] Simultaneously, μ was measured. 1-2 intensity get The value of μ can be used to calculate the output state μ. out The intensity I of the output state can be divided into the following three categories:

[0040] I v = (0, I1), I d = (I1, I2), I s = (I2, I3),

[0041] Where I3 = 2μt, and I2 and I1 are selected according to the actual situation. Among these three states, we will... s Let I be the signal state. v and I d This is denoted as the decoy state and used for subsequent decoy state analysis.

[0042] Step 2: The information receiver repeats Step 1 to generate a series of photon pulse sequences and sends them to the information sender Alice.

[0043] Step 3: The sender stores the received photon pulse sequence. Then, the receiver and sender, after consultation, select a subset of photon pulses for the first round of security testing. The receiver publishes the encoding and intensity information of the photon pulses at the corresponding positions. The sender categorizes the measurement results of the photon pulses into three classes based on the receiver's intensity information and estimates the bit error rate using a decoy state method. If the bit error rate exceeds a pre-set threshold, the security test fails, and communication terminates. If the bit error rate is below the threshold, communication continues.

[0044] The pulses used for the first round of security testing include all decoy state pulses and a portion of signal state pulses.

[0045] The information sender estimates the reception rate and error rate of the three types of pulses based on the information published by the information receiver, and then estimates the reception rate and error rate of single photons and two photons in the pulse, thus completing the decoy state method estimation.

[0046] Step 4: The information sender randomly selects a portion of the remaining signal-state photon pulses for random encoding, and encodes the remaining signal-state photon pulses for information encoding. After encoding, the information is sent to the information receiver.

[0047] The encoding operation is as follows:

[0048] U0=|H> <H|||V><V|,U1=|V><H| |H><V|

[0049] Here, H and V represent the horizontal and vertical polarization of the photon, respectively.

[0050] The random encoding uses U0 and U1 codes randomly. The information encoding selects U0 and U1 codes according to the information to be sent. U0 represents information 0 and U1 represents information 1.

[0051] Step 5: The information receiver performs X-basis or Z-basis measurements on the received photon pulses based on its own random coding information.

[0052] When the initial state sent by the information receiver is |H> and |V>, it performs Z-basis measurement; when the initial state sent by the information receiver is |+> and |->, it performs X-basis measurement.

[0053] Step 6: The sender publishes the location and random coding information of the randomly coded photon pulse. The receiver compares the measurement results at the corresponding location to estimate the bit error rate. If the bit error rate is higher than a pre-set threshold, the security check fails and communication is terminated. If the bit error rate is lower than the threshold, communication continues.

[0054] Step 7: The information receiver reconstructs the information sender's information through classical post-processing based on the measurement information of photon pulses at other locations.

[0055] Example 2:

[0056] like Figure 2 As shown, this embodiment of the invention also provides a quantum-secure direct communication system, including an information receiver and an information sender. The communication method is described in [reference needed]. Figure 1 The information receiver generates photon pulses of random intensity using a passive decoy source and sends them to the information sender. The sender receives and stores the pulses, then selects a subset for the first round of security checks. After passing the security check, the sender encodes the information and performs random encoding, then sends the encoded photons back to the receiver, which performs decoding and the second round of security checks. The specific steps involved are detailed in Example 1 and will not be repeated here for brevity. Figure 4 This describes the relationship between the secure information capacity and communication distance of the quantum-secure direct communication method provided in this embodiment of the invention under different strengths.

[0057] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can 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.) containing computer-usable program code.

[0058] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0059] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0060] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles 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 quantum-secure direct communication method based on passive decoy states, characterized in that: The method includes the following steps: Step 1: The information recipient prepares two [information] with [strength / intensity]... Coherent pulses with random phase, coherent pulses with random phase, coherent pulses , Pulses are generated by interference through a beam splitter. , ,Measurement get The intensity information is used to classify photon pulses into three categories based on their intensity; then the pulses are further classified... The input is fed into the encoder, where it is randomly encoded, and the output state is... ; Step 2: The information receiver repeats Step 1 to generate a series of photon pulse sequences and sends them to the information sender; Step 3: The sender stores the received photon pulse sequence; then, the receiver and sender agree to select a subset of photon pulses for the first round of security checks; the receiver publishes the encoding and intensity information of the photon pulses at the corresponding positions, and the sender classifies the measurement results of the photon pulses into three categories based on the receiver's intensity information. A decoy state method is used to estimate the bit error rate (BER). Specifically, the sender estimates the receiver rate and error rate for each of the three types of pulses, and then estimates the receiver rate and error rate for single-photon and two-photon signals within the pulses. If the BER is higher than a pre-set threshold, the security check fails and communication is terminated; if the BER is lower than the threshold, communication continues. Step 4: The information sender randomly selects a portion of the remaining signal-state photon pulses for random encoding, and encodes the remaining signal-state photon pulses for information encoding; after encoding, the information is sent to the information receiver through the quantum channel; Step 5: The information receiver performs X-basis or Z-basis measurements on the received photon pulses based on its own random coding information; Step 6: The information sender publishes the location and random coding information of the randomly coded photon pulse. The information receiver compares the measurement results of the corresponding location and estimates the bit error rate. When the bit error rate is higher than a pre-set threshold, the security check fails and communication is terminated. When the bit error rate is lower than the threshold, communication continues. Step 7: The information receiver reconstructs the information sender's information through classical post-processing based on the measurement information of photon pulses at other locations.

2. The quantum-secure direct communication method based on a passive decoy state according to claim 1, characterized in that: The two strengths mentioned in step 1 are A coherent pulse with random phase is described as follows: ； in Indicates the intensity of the coherent pulse; It is a natural constant; Represents the random phase of a coherent pulse; It is an imaginary number. .

3. The quantum-secure direct communication method based on a passive decoy state according to claim 2, characterized in that: The coherent pulse generated by beam splitter interference in step 1 , The expression is as follows: ； in, Let be the transmittance of the beam splitter, and .

4. The quantum-secure direct communication method based on a passive decoy state according to claim 3, characterized in that: The pulse described in step 1 The input is fed into the encoder, where it undergoes random encoding, and the resulting output state is... The expression is as follows: ； in Output state The strength, ， ， ； ； in The operator that generates the quantum state of a randomly encoded photon.

5. A quantum-secure direct communication method based on a passive decoy state according to claim 4, characterized in that: The measurement described in step 1 get The intensity information is used to classify photon pulses into three categories based on their intensity: specifically, by measuring... intensity ,get The value is used to calculate the output state. intensity Output state intensity They are divided into the following three categories: ； in, , and Select according to the actual situation; among these three types, This is denoted as the signal state. and This is denoted as the decoy state and used for subsequent decoy state analysis.

6. A quantum-secure direct communication method based on a passive decoy state according to claim 5, characterized in that: In step 3, the information receiver and the information sender agree to select a portion of photon pulses for the first round of security testing. Specifically, the information receiver and the information sender select all decoy state pulses and a portion of signal state pulses for security testing.

7. A quantum-secure direct communication method based on a passive decoy state according to claim 6, characterized in that: In step 4, the information sender performs information encoding and random encoding on the signal-state photons in its hand, wherein the encoding operation is as follows: ， ； Where H and V represent the horizontal and vertical polarization of the photon, respectively; Random encoding used randomly and Encoding: The information encoding is selected based on the information to be sent. and coding, Indicates information 0, Indicates information 1.

8. A quantum-secure direct communication method based on a passive decoy state according to claim 7, characterized in that: In step 5, the information receiver performs X-basis or Z-basis measurements on the received photons based on its own random coding information. Specifically, when the initial state sent by the information receiver is... and At that time, Z-basis measurement is performed; when the initial state sent by the information receiver is and At that time, X-base measurements were performed.

9. A quantum-safe direct communication system, characterized in that, It includes an information sender and an information receiver, and is used to perform the steps corresponding to the method described in any one of claims 1 to 8.

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