Quantum secure direct communication method and system based on passive decoy state

Abstract

The invention discloses a quantum secure direct communication method and system based on a passive decoy state, an information receiver uses two coherent pulses with random phases, and the two coherent pulses are interfered and attenuated through a beam splitter to generate weak coherent pulse beams with random intensity. And the information receiver randomly encodes the weak coherent pulse and sends the weak coherent pulse to the information sender. And the information sender carries out information coding and then sends the photon pulse to the information receiver. And the information receiver decodes according to the pulse information initially sent by the information receiver and restores the information sent by the information sender. The method does not need to actively modulate the intensity of the light source, can realize a passive decoy state, can be realized by using a linear optical device, simplifies the experiment operation, resists the side channel attack of a third-party eavesdropper to the light source modulator, and can enhance the security of quantum secure direct communication.

Description

Technical Field

[0001] The present invention belongs to the field of quantum communication, and in particular relates to a quantum secure direct communication method and system based on passive decoy states. Background Art

[0002] Quantum secure direct communication (QSDC) is an important branch of quantum communication. It can directly and securely transmit information between the 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 team 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, the equipment is not perfect. These defective devices may give third-party eavesdroppers an opportunity to take advantage of and threaten the security of the protocol. In 2020, Pan Dong et al. analyzed the secure information capacity of the QSDC protocol of weak dry pulse light sources considering collective attacks and photon number splitting attacks, and they used the decoy state method for parameter estimation. However, the imperfection of the light source causes the pulses it produces to contain vacuum state and multi-photon components. When the intensity of the light source is actively modulated using the entrapped state method, some security vulnerabilities are introduced, and third-party eavesdroppers can perform Trojan horse attacks to steal information. In 2009, Curty et al. proposed a passive entrapped state method, which can passively prepare entrapped states through two beams of coherent light with random phases. No additional active modulation operations are required, which can simplify the experimental setup and eliminate the side channel information leakage caused by active operations. At present, the passive entrapped state method using coherent light has not been applied to QSDC. Summary of the invention

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

[0004] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

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

[0006] Step 1: The information receiver prepares two coherent pulses with intensity μ and random phase. 1 , μ 2 Generation of pulse μ by beam splitter interference 1+2 , μ 1-2 , measure μ 1-2Get μ 1+2 The intensity information of the photon pulses is obtained and the photon pulses are divided into three categories according to the intensity. 1-2 Input into the encoder, perform random encoding, and output 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 information sender stores the received photon pulse sequence. Then the information receiver and the information sender discuss and select a part of the photon pulses for the first round of security detection. The information receiver publishes the coding information and intensity information of the photon pulses at the corresponding position. The information sender divides the measurement results of the photon pulses into three categories according to the intensity information of the information receiver, and estimates the bit error rate using the decoy state method. When the bit error rate is higher than the pre-set threshold, the security detection fails and the communication is terminated. When the bit error rate is lower than the threshold, the 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. After encoding, it is sent to the information receiver.

[0010] Step 5: The information receiver performs X-basis or Z-basis measurement on the received photon pulse according to its own randomly encoded information.

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

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

[0013] A quantum secure direct communication system, an information sender, and an information receiver are used to execute the quantum secure direct communication method based on passive decoy state of the present invention.

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

[0015] (1) The quantum secure direct communication method based on passive entrapped states proposed in the present invention uses the entrapped state method to resist photon number splitting attacks and coherent attacks, thereby improving the security capacity of quantum secure direct communication, and increasing the communication distance and security information capacity.

[0016] (2) The quantum secure direct communication method based on passive entrapped states proposed in the present invention can passively modulate the entrapped state intensity without the need for additional active modulation, and can resist side channel attacks on the light source modulator, thereby improving the security of quantum secure direct communication.

[0017] (2) The quantum secure direct communication method based on passive entrapped states proposed in the present invention uses linear optical devices, which is conducive to practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of a quantum secure direct communication method provided by an embodiment of the present invention;

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

[0020] Figure 3 is a structural diagram of a passive decoy state provided by an embodiment of the present invention;

[0021] Figure 4 It is the relationship between the secure information capacity and the channel loss at different intensities of the quantum secure direct communication method provided by the embodiment of the present invention, wherein the x-axis is the channel loss and the y-axis is the secure information capacity. DETAILED DESCRIPTION

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

[0023] Embodiment 1:

[0024] As attached Figure 1 As shown, this embodiment is a quantum secure direct communication method based on passive decoy state, comprising the following steps

[0025] Step 1: Figure 3 As shown, the information receiver Bob prepares two coherent pulses with intensity μ and random phase. 1 , μ 2 The pulse μ is generated by beam splitter (BS) interference 1+2 , μ 1-2 , measure μ 1-2 Get μ 1+2 The intensity information of the photon pulses is obtained and the photon pulses are divided into three categories according to the intensity. 1-2 Input into the encoder, perform random encoding, and output state μ out .

[0026] Among them, two coherent pulses with intensity μ and random phase are expressed as:

[0027]

[0028] Where μ represents the intensity of the coherent pulse; e is a natural constant; φ 1 ,φ 2 represents the random phase of the coherent pulse; j is an imaginary number, j 2 =-1.

[0029] The pulse μ 1 , μ 2 The pulse μ generated by beam splitter interference 1+2 , μ 1-2 It is expressed as:

[0030]

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

[0032] Afterwards, the coherent pulse μ 1-2 Input to the encoder, perform random encoding, and output μ out It is expressed as:

[0033]

[0034] Where I is the output state μ ou The strength of t,

[0035] I=2μt(cos 2 θ),

[0036]

[0037]

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

[0039] At the same time, measure μ 1-2 Strength get The value of the output state μ can be calculated out The intensity I of the output state can be divided into the following three categories:

[0040] I v =(0,I 1 ), I d =(I 1 , I 2 ), I s =(I 2 , I 3 ),

[0041] Among them, I3 =2μt,I 2 and I 1 Select according to the actual situation. In these three states, we will s Denoted as signal state, I v and I d It is recorded as the decoy state and used in the 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 information sender stores the received photon pulse sequence. Then the information receiver and the information sender discuss and select a part of the photon pulses for the first round of security detection. The information receiver publishes the coding information and intensity information of the photon pulses at the corresponding position. The information sender divides the measurement results of the photon pulses into three categories according to the intensity information of the information receiver, and estimates the bit error rate using the decoy state method. When the bit error rate is higher than the pre-set threshold, the security detection fails and the communication is terminated. When the bit error rate is lower than the threshold, the communication continues.

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

[0045] The information sender estimates the reception rates and error rates of the three types of pulses based on the information published by the information receiver, and then estimates the reception rates and error rates of single photons and double photons in the pulses to complete the estimation of the entrapped state method.

[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. After encoding, it is sent to the information receiver.

[0047] The encoding operation is

[0048] U 0 =|H> <H|||V><V|,U 1 =|V> <H| |H><V|

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

[0050] Random code Random use U 0 and U 1 Coding, information coding selects U according to the information to be sent 0 and U 1 Coding, U 0 Indicates information 0, U 1 Indicates information 1.

[0051] Step 5: The information receiver performs X-basis or Z-basis measurement on the received photon pulse according to its own randomly encoded information.

[0052] When the initial states sent by the information receiver are |H> and |V>, he performs Z-basis measurement. When the initial states sent by the information receiver are |+> and |->, he performs X-basis measurement.

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

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

[0055] Embodiment 2:

[0056] like Figure 2 As shown, the embodiment of the present invention also provides a quantum secure direct communication system, including an information receiver and an information sender. The communication method thereof is shown in Figure 1 . The information receiver prepares photon pulses of random intensity through a passive decoy state source and sends them to the information sender. The information sender stores the received photons and then selects a portion of the photons for the first round of security testing. After the security test is passed, the information sender performs information encoding and random encoding, and then sends the encoded photons to the information receiver, who performs decoding and a second round of security testing. For the specific method steps they perform, please refer to Example 1. In order to save space, they will not be repeated here. Figure 4 This is the relationship between the security information capacity and communication distance of the quantum secure direct communication method provided by an embodiment of the present invention at different intensities.

[0057] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0058] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0059] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0060] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A quantum secure direct communication method based on passive decoy state, characterized by: The method comprises the following steps: Step 1: 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 to generate pulse μ 1+2 , μ 1-2 , measure μ 1-2 Get μ 1+2 The intensity information of the photon pulses is obtained, and the photon pulses are divided into three categories according to the intensity; then the pulses μ 1-2 Input into the encoder, perform random encoding, and output state μ out ; 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 information sender stores the received photon pulse sequence; then the information receiver and the information sender discuss and select a part of the photon pulses for the first round of security detection; the information receiver publishes the coding information and intensity information of the photon pulses at the corresponding position, and the information sender divides the measurement results of the photon pulses into three categories according to the intensity information of the information receiver, and uses the decoy state method to estimate the bit error rate; when the bit error rate is higher than the pre-set threshold, the security detection fails and the communication is terminated; when the bit error rate is lower than the threshold, the 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; after the encoding is completed, it is sent to the information receiver through the quantum channel; Step 5: The information receiver performs X-basis or Z-basis measurement on the received photon pulse according to its own random coded information; Step 6: The information sender publishes the position and random coding information of the randomly coded photon pulse, and the information receiver compares the measurement results of the corresponding position and estimates the bit error rate; when the bit error rate is higher than the preset threshold, the security check fails and the communication is terminated; when the bit error rate is lower than the threshold, the communication continues; Step 7: The information receiver restores the information of the information sender through classical post-processing based on the measurement information of photon pulses at other locations.

2. According to claim 1, a quantum secure direct communication method based on passive decoy state is characterized in that: The two coherent pulses of intensity μ and random phase described in step 1 are expressed as: Where μ represents the intensity of the coherent pulse; e is a natural constant; φ1, φ2 represent the random phases of the coherent pulse; j is an imaginary number, j 2 =-1.

3. According to claim 1, a quantum secure direct communication method based on passive decoy state is characterized in that: The coherent pulse μ generated by beam splitter interference in step 1 1+2 , μ 1-2 It is expressed as: Wherein, t is the transmittance of the beam splitter, and t<<1.

4. According to claim 1, a quantum secure direct communication method based on passive decoy state is characterized in that: As described in step 1, pulse μ 1-2 Input into the encoder, perform random encoding, and generate the output state μ out It is expressed as: Where I is the output state μ out The strength of I=2μt(cos 2 i), in Represents the generation operator of quantum states of randomly encoded photons.

5. According to claim 1, a quantum secure direct communication method based on passive decoy state is characterized in that: Measure μ as described in step 1 1-2 Get μ 1+2 The intensity information of the photon pulses is divided into three categories according to the intensity: 1-2 Strength get The value of , thus calculating the output state μ out The intensity I of the output state is divided into the following three categories: I v =(0,I1),I d =(I1,I2),I s =(I2,I3) Among them, I3=2μt, I2 and I1 are selected according to the actual situation; in these three states, I s Denoted as signal state, I v and I d It is recorded as the decoy state and used in the subsequent decoy state analysis.

6. According to claim 1, a quantum secure direct communication method based on passive decoy state is characterized in that: The information receiver and the information sender described in step 3 select a part of the photon pulses for the first round of security detection after consultation. Specifically, the information receiver and the information sender select all the decoy state pulses and a part of the signal state pulses for security detection.

7. The method of quantum secure direct communication based on passive decoy state according to claim 1, characterized in that: The information sender described in step 3 divides the measurement results of the photon pulse into three categories according to the intensity information of the information receiver, and uses the entrapped state method to estimate the bit error rate. Specifically, the information sender estimates the reception rate and error rate of the three types of pulses respectively, and then estimates the reception rate and error rate of single photons and double photons in the pulse.

8. The method of quantum secure direct communication based on passive decoy state according to claim 1, characterized in that: The information sender in step 4 performs information encoding and random encoding on the signal state photons in the hand, where the encoding operation is U0=|H> <H|+|V><V|,U1=|V><H|-|H><V| Among them, H and V represent the horizontal polarization and vertical polarization of the photon, respectively; Random coding randomly uses U0 and U1 coding, and information coding selects U0 and U1 coding according to the information to be sent. U0 represents information 0 and U1 represents information 1.

9. The method of quantum secure direct communication based on passive decoy state according to claim 8, characterized in that: The information receiver described in step 5 performs X-basis or Z-basis measurement on the received photons according to its own randomly encoded information. Specifically, when the initial state sent by the information receiver is |H> and |V, it performs Z-basis measurement, and when the initial state sent by the information receiver is |+> and |->, it performs X-basis measurement.

10. A quantum secure direct communication system, characterized in that: An information sender and an information receiver are used to execute the steps corresponding to the method described in any one of claims 1 to 9.

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