Quantum secure direct communication method based on symmetric all-passive light source

Abstract

The invention discloses a quantum secure direct communication method based on a symmetric all-passive light source, and the method comprises the steps: an information receiver uses four coherent pulses with random phases, generates weak coherent pulse beams with random intensity and random quantum states through the interference, beam combination and attenuation of a beam splitter and a polarization beam splitter, and transmits the weak coherent pulse beams to an information transmitter; and the information sender sends the photon pulse to the information receiver after coding. 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. According to the method, the intensity of the light source and the quantum state do not need to be actively modulated, the passive decoy state and the passive coding can be realized at the same time, the experimental operation can be simplified, the side channel attack of a third-party eavesdropper on the light source modulator can be resisted, and the security of quantum secure direct communication is enhanced.

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 based on a symmetrical fully passive light source. Background Art

[0002] Quantum secure direct communication (QSDC) is an important branch of quantum communication. It can directly and securely transmit information between the two 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, Zhou Zengrong et al. proposed a measurement device-independent (MDI) quantum secure direct communication protocol, which can resist all attacks on the measurement device side. However, the imperfection of the light source end device will also introduce some security vulnerabilities, especially when we actively modulate the light intensity and quantum state, third-party eavesdroppers can perform Trojan horse attacks to steal information. In 2023, Wang et al. proposed the idea of ​​a fully passive light source. In the same year, their group proposed an improved symmetric fully passive light source. Passive coding and passive entrapment state selection are achieved through phase-random coherent pulses. Using this symmetric fully passive light source, there is no need to actively modulate the entrapment state light intensity, nor is there any need to perform active coding operations. This can simplify the experimental setup and eliminate side channel information leakage caused by active operations. Moreover, this method does not require screening of the coded particles, which can greatly reduce losses. At present, the symmetric fully passive light source technology has not yet been applied to the QSDC protocol. 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 a symmetric fully passive light source, 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 a symmetrical fully passive light source comprises the following steps:

[0006] Step 1: The information receiver prepares four coherent pulses with intensity μ and random phase. Pulses μ1 and μ2 are interfering with each other to generate pulse μ 1+2 , μ 1-2, pulses μ3 and μ4 generate pulse μ through BS interference 3+4 , μ 3-4 , measure μ 1+2 and μ 3+4 Get μ 1-2 and μ 3-4 The intensity and phase information of the pulse μ 1-2 With pulse μ 3-4 Synthesize a bundle of μ by PBS 1-2+3-4 , and then attenuated into weak coherent pulse μ by the intensity attenuator out The information receiver shall 1+2 and μ 3+4 The measurement results are used to filter out the states that you want to send and send them to the sender of the information.

[0007] Step 2: The information sender stores the received photon pulses. Then the information receiver and the information sender discuss and select a portion of photons for the first round of security testing. The information receiver publishes the information of the photons at the corresponding position, and the information sender estimates the bit error rate based on the information of the information receiver. When the bit error rate is lower than the threshold, communication continues.

[0008] Step 3: The information sender randomly selects a portion of the remaining signal state photons for random encoding, and encodes the remaining signal state photons for information. After encoding, it is sent to the information receiver.

[0009] Step 4: The information receiver performs X-basis or Z-basis measurement on the received photons.

[0010] Step 5: The information sender publishes the position and random coding information of the randomly coded photons. The information receiver compares the measurement results of the corresponding positions and estimates the bit error rate. When the bit error rate is lower than the threshold, communication continues.

[0011] Step 6: The information receiver restores the information of the sender through classical post-processing based on the measurement information of photons at other locations.

[0012] Furthermore, the four coherent pulses with intensity μ and random phases described in step 1 are expressed as:

[0013]

[0014]

[0015] Where μ represents the intensity of the four coherent pulses; α, β, γ, δ represent the random phases of the four coherent pulses; j is an imaginary number, j 2 =-1. And the photons in μ1 and μ2 are in the quantum state The photons in μ3 and μ4 are in a quantum state where |H> and |V> are the horizontal and vertical polarizations of the photon, respectively.

[0016] Furthermore, the pulse μ described in step 1 1+2 , μ 1-2 , μ 3+4 , μ 3-4 , μ 1-2+3-4 and μ out It is expressed as:

[0017]

[0018]

[0019] The subscripts R and L represent the quantum states of the photons in the pulse.

[0020]

[0021] in

[0022]

[0023]

[0024]

[0025]

[0026] is the quantum state of the photon in the pulse.

[0027] Furthermore, the information receiving party described in step 1 receives information according to μ 1+2 and μ 3+4 The measurement results filter out the states that you want to send. Specifically, the information receiver uses μ 1+2 and μ 3+4 The measurement results are used to calculate μ out When I, θ, φ satisfy the following interval, a photon pulse is sent to the information sender.

[0028] φ∈(φ x -Δφ,φ x +Δφ)

[0029]

[0030] Among them, Δθ and Δφ are selected according to the actual system. x Take 0, π, When I is , the states sent are recorded as |H>, |V>, |+>, |->. In addition, the information receiver will also record the state as vacuum state (vac), decoy state (d), and signal state (s) according to the size of I. That is, there are a total of 4*3=12 states sent by the information receiver.

[0031] Furthermore, a portion of photons are selected as described in step 2 for the first round of safety detection, specifically including all vacuum state photons, all decoy state photons, and a portion of signal state photons randomly selected.

[0032] Furthermore, the information sender in step 3 performs information encoding and random encoding on the photons in hand. The encoding operation is:

[0033] U0=|H> <H|+|V><V|,U1=|V><H|-|H><V|。

[0034] 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.

[0035] Furthermore, the information receiver described in step 4 performs X-basis or Z-basis measurement on the received photons. Specifically, when the initial state sent by the information receiver is |H> and |V>, Z-basis measurement is performed, and when the initial state sent by the information receiver is |+> and |->, X-basis measurement is performed.

[0036] The present invention has the following beneficial effects:

[0037] 1. The quantum secure direct communication method based on a symmetric fully passive light source proposed in the present invention uses a decoyed state method, which can resist photon number splitting attacks and coherent attacks, improve the security capacity of quantum secure direct communication, and increase the communication distance.

[0038] 2. The quantum secure direct communication method based on a symmetric fully passive light source proposed in the present invention can passively modulate the intensity of the decoy state and the quantum state, can resist side channel attacks against the light source modulator, and improve the security of quantum secure direct communication.

[0039] 3. The quantum secure direct communication method based on symmetrical all-passive light source proposed in the present invention uses a symmetrical light source to make the generated Z-based and X-based quantum states symmetrical to each other, which can greatly reduce the complexity of experimental data processing. In addition, there is no need to filter and discard the data, which can effectively improve resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of a quantum secure direct communication method provided by an embodiment of the present invention;

[0041] Figure 2This is a structural principle block diagram of a quantum secure direct communication system provided by an embodiment of the present invention;

[0042] Figure 3 is a structural diagram of a symmetrical fully passive light source provided by an embodiment of the present invention;

[0043] Figure 4 This is a comparison chart of the optimal performance of the quantum secure direct communication method provided by an embodiment of the present invention and the existing active modulation light source solution. DETAILED DESCRIPTION

[0044] 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.

[0045] Embodiment 1:

[0046] As attached Figure 1 As shown, the quantum secure direct communication implementation scheme of this embodiment includes the following steps:

[0047] Step 1: Figure 3 As shown in the figure, the information receiver Bob prepares four coherent pulses with intensity μ and random phase. Pulses μ1 and μ2 are generated by BS interference to generate pulse μ 1+2 , μ 1-2 , pulses μ3 and μ4 generate pulse μ through BS interference 3+4 , μ 3-4 , measure μ 1+2 and μ 3+4 Get μ 1-2 and μ 3-4 The intensity and phase information of the pulse μ 1-2 With pulse μ 3-4 Synthesize a bundle of μ by PBS 1-2+3-4 , and then attenuated into weak coherent pulse μ by the intensity attenuator out The information receiver shall 1+2 and μ 3+4 The measurement results filter out the states you want to send and send them to the information sender Alice.

[0048] The four coherent pulses with intensity μ and random phases are:

[0049]

[0050]

[0051] Where μ represents the intensity of the four coherent pulses; α, β, γ, δ represent the random phases of the four coherent pulses; j is an imaginary number, j 2=-1. And the photons in μ1 and μ2 are in the quantum state The photons in μ3 and μ4 are in a quantum state where |H> and |V> are the horizontal and vertical polarizations of the photon, respectively.

[0052] The pulse μ after BS interference 1+2 , μ 1-2 and μ 3+4 , μ 3-4 for

[0053]

[0054]

[0055] After PBS beam combination, the pulse μ 1+2+3+4 for:

[0056]

[0057] Finally, it decays to μ through BS out :

[0058]

[0059] in

[0060]

[0061]

[0062]

[0063]

[0064] is the quantum state of the photon in the pulse.

[0065] The information receiver is based on μ 1+2 and μ 3+4 The measurement results are used to calculate μ out When I, θ, φ satisfy the following interval, a photon pulse is sent to the information sender.

[0066] φ∈(φ x -Δφ,φ x +Δφ)

[0067]

[0068] Among them, Δθ and Δφ are selected according to the actual system. x Take 0, π, When , the sent state is recorded as |H>, |V>, |+>, |->. Among them, In addition, the information receiver will also record the state as vacuum state (vac), decoy state (d), or signal state (s) according to the size of I.

[0069] Step 2: The information sender stores the received photon pulses. Then a portion of photons are randomly selected for the first round of security testing. The information receiver publishes the information of the photons at the corresponding position. The information sender estimates the bit error rate based on the information of the information receiver. When the bit error rate is lower than the threshold, communication continues.

[0070] A portion of photons are selected for the first round of safety testing, including all vacuum state photons, all decoy state photons, and a randomly selected portion of signal state photons.

[0071] Step 3: The information sender randomly selects a portion of the remaining signal state photons for random encoding, and encodes the remaining signal state photons for information. After encoding, it is sent to the information receiver.

[0072] The encoding operation is

[0073] U0=|H> <H|+|V><V|,U1=|V><H|-|H><V|。

[0074] 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.

[0075] Step 4: The information receiver performs X-basis or Z-basis measurement on the received photons.

[0076] When the initial state sent by the information receiver is |H> and |V>, Z-basis measurement is performed, and when the initial state sent by the information receiver is |+> and |->, X-basis measurement is performed.

[0077] Step 5: The information sender publishes the position and random coding information of the randomly coded photons. The information receiver compares the measurement results of the corresponding positions and estimates the bit error rate. When the bit error rate is lower than the threshold, communication continues.

[0078] Step 6: The information receiver restores the information of the sender through classical post-processing based on the measurement information of photons at other locations.

[0079] Figure 4 This is a comparison chart of the optimal performance of the quantum secure direct communication method provided by the embodiment of the present invention and the existing active modulated light source solution. The quantum secure direct communication method based on a symmetrical fully passive light source proposed by the present invention uses a light source with a symmetrical structure, so that the generated Z-based and X-based quantum states are symmetrical to each other, which can greatly reduce the complexity of experimental data processing. In addition, there is no need to filter and discard the data, which can effectively improve resource utilization.

[0080] Embodiment 2:

[0081] 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 with random intensity and quantum state through a fully passive light 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.

[0082] Those skilled in the art will appreciate that embodiments of the present invention 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 on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0083] The present invention 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 block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks 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.

[0084] 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.

[0085] 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.

[0086] 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 a symmetrical fully passive light source, characterized in that: The method comprises the following steps: Step 1: The information receiver prepares four coherent pulses with intensity μ and random phase. Pulses μ1 and μ2 are interfering with each other to generate pulse μ 1+2 , μ 1-2 , pulses μ3 and μ4 generate pulse μ through BS interference 3+4 , μ 3-4 , measure μ 1+2 and μ 3+4 Get μ 1-2 and μ 3-4 The intensity and phase information of the pulse μ 1-2 With pulse μ 3-4 Synthesize a bundle of μ by PBS 1-2+3-4 , and then attenuated into weak coherent pulse μ by the intensity attenuator out , the information receiver is based on μ 1+2 and μ 3+4 The measurement results filter out the states that you want to send and send them to the sender of the information; Step 2: The information sender stores the received photon pulses, and then the information receiver and the information sender discuss and select a part of the photons for the first round of security detection. The information receiver publishes the information of the photons at the corresponding position. The information sender estimates the bit error rate based on the information of the information receiver. When the bit error rate is lower than the threshold, communication continues; Step 3: The information sender randomly selects a portion of the remaining signal state photons for random encoding, and encodes the remaining signal state photons for information, and after encoding, sends them to the information receiver; Step 4: The information receiver performs X-based or Z-based measurement on the received photons; Step 5: The information sender publishes the position and random coding information of the randomly coded photons, and the information receiver compares the measurement results of the corresponding positions and estimates the bit error rate. When the bit error rate is lower than the threshold, the communication continues; Step 6: The information receiver restores the information of the sender through classical post-processing based on the measurement information of photons at other locations.

2. According to claim 1, a quantum secure direct communication method based on a symmetrical fully passive light source is characterized in that: The four coherent pulses of intensity μ and random phase described in step 1 are expressed as: Where μ represents the intensity of the four coherent pulses; α, β, γ, δ represent the random phases of the four coherent pulses; j is an imaginary number, j 2 =-1; the subscripts R and L represent the quantum state of the photons in the coherent light, where R represents the quantum state of the photons L indicates that the photon is in a quantum state where |H> and |V> are the horizontal and vertical polarizations of the photon, respectively.

3. According to claim 1, a quantum secure direct communication method based on a symmetrical fully passive light source is characterized in that: The pulse μ described in step 1 1+2 , μ 1-2 , μ 3+4 , μ 3-4 , μ 1-2+3-4 and μ out It is expressed as: Among them, the subscripts R and L represent the quantum state of the photons in the pulse; in in The quantum state of the photon in the pulse is 4. According to claim 1, a quantum secure direct communication method based on a symmetrical fully passive light source is characterized in that: The information receiver described in step 1 is based on μ 1+2 and μ 3+4 The measurement results filter out the states that you want to send. Specifically, the information receiver uses μ 1+2 and μ 3+4 The measurement results are used to calculate μ out When I, θ, φ satisfy the following intervals, the photon pulse is sent to the information sender; φ∈(φ x -△φ,φ x +△φ) Among them, Δθ and Δφ are selected according to the actual system needs, φ x The values ​​of are 0, π, The corresponding states sent are recorded as |H>, |V>, |+>, |->; the information receiver will record the state as vacuum state (vac), decoy state (d), or signal state (s) according to the size of I, that is, there are a total of 4*3=12 states sent by the information receiver.

5. According to claim 1, a quantum secure direct communication method based on a symmetrical fully passive light source is characterized in that: As described in step 2, a portion of photons are selected for the first round of safety testing, specifically including all vacuum state photons, all decoy state photons, and a portion of signal state photons randomly selected.

6. According to claim 1, a quantum secure direct communication method based on a symmetrical fully passive light source is characterized in that: The information sender in step 3 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|。 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.

7. According to claim 1, a quantum secure direct communication method based on a symmetrical fully passive light source is characterized in that: The information receiver described in step 4 performs X-based or Z-based measurement on the received photons. Specifically, when the initial state sent by the information receiver is |H> and |V>, Z-based measurement is performed, and when the initial state sent by the information receiver is |+> and |->, X-based measurement is performed.

8. A quantum secure direct communication system, characterized in that: It includes an information sender and an information receiver for executing the communication method described in any one of claims 1 to 7.

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