Controlled quantum secure direct communication method based on multiple Bell bases

Abstract

A controlled quantum secure direct communication method based on multiple groups of Bell bases comprises the following steps: a third party prepares a series of entangled photon pairs to form two photon sequences, and the two photon sequences are respectively sent to two communication parties; and the two communication parties select photons on the photon sequence for two rounds of safety detection. And the third party publishes a preparation base of the entangled photon pair, and an information receiver performs Bell state measurement and records a result according to the preparation base. An information sender publishes random coding positions and coding information, a third party publishes initial states on the positions, a receiver performs second round of security detection, and it is indicated that the channel is free of eavesdropping when the bit error rate is lower than a threshold value. And finally, the third party publishes the initial states of other positions, and the receiver deduces the information to be transmitted by the sender according to the Bell state measurement result. According to the method, only the Bell state needs to be used for communication, and only two rounds of transmission and two rounds of security detection are needed, so that the implementation complexity of a protocol can be reduced, and the communication efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of quantum secure communication, and particularly relates to a controlled quantum secure direct communication method based on multiple groups of Bell bases. BACKGROUND

[0002] Quantum secure direct communication (QSDC) is a major progress of quantum secure communication, and has a milestone significance: the information sender directly transmits ciphertext in the channel, without the need of preparing quantum key. In 2000, Long Guilu and Liu Xiaoshu first proposed the idea of QSDC. In 2003, Deng Fuguo et al. proposed a two-step QSDC protocol based on EPR entangled pairs by using dense coding and distributed transmission; the following year, Deng Fuguo and Long Guilu of the research group proposed a one-time pad quantum secure direct communication scheme: using single-photon states to directly encode and transmit ciphertext, which is referred to as "DL04" protocol; in recent years, new QSDC protocols have emerged in an endless stream, and a controlled QSDC has been developed, in which the communication receiver can only decode the ciphertext with the permission of all control terminals, which can effectively enhance the security of QSDC. In 2006, Wang et al. used GHZ state as a quantum ciphertext information carrier to realize a controlled quantum secure direct communication scheme. Further, in 2008, Chen et al. used the robustness of W state to propose an anti-interference controlled QSDC in which a sequence of photons is used to encode and send to the communication parties; in 2011, Wang et al. proposed a phase-encrypted controlled quantum secure direct communication; in 2012, Jing et al. applied a five-particle cluster state to the controlled QSDC, which can effectively increase the eavesdropping detection rate to 89%. In particular, a more credible third party is introduced in the communication process, which is responsible for the preparation and distribution of information carriers, and each channel is only used for transmitting one round of information, which can improve the security of the protocol.

[0003] Most of the current controlled QSDC uses multi-particle entanglement, which is difficult to directly prepare, limiting the application of the protocol. Some controlled QSDC protocols use Bell state protocols, but they need to perform three rounds of transmission, which requires three times of security detection and increases resource consumption. In order to improve the efficiency of QSDC and reduce the implementation difficulty, the present application proposes a controlled QSDC method based on multiple groups of Bell bases. Compared with the controlled QSDC protocol based on multiple particles, the present application only needs to use two groups of two-photon entanglement under Bell base, which can reduce the complexity of source preparation. Compared with the controlled QSDC protocol using Bell state, the present application can reduce one round of security detection process, effectively reduce resource consumption, and improve communication efficiency. SUMMARY

[0004] The present application proposes a controlled quantum secure direct communication method based on multiple groups of Bell bases, which not only reduces the requirement for quantum state preparation of the light source, but also effectively reduces the resource consumption of communication, thereby improving the efficiency of quantum secure direct communication.

[0005] A controlled quantum-secure direct communication method based on multiple sets of Bell bases includes the following steps: Step 1: Third-party Chalice preparation n + l + m Take entangled photon pairs, and then take one photon from each entangled photon pair to form an ordered photon sequence S. A Distribute the photons to Alice; form the remaining photons into a photon sequence S. B Distribute it to Bob; Step 2: After receiving the photon sequence, Alice randomly selects... l Single-photon measurements were performed using randomly selected photons as a basis for security detection, and the results in the photon sequence S were published. A Position and measurement results in the photon sequence S; Bob's measurement of the photon sequence S B The photons at the corresponding positions are randomly selected for basis measurement, and the measurement basis and measurement results are recorded for the first round of security checks; both parties store the remaining photons in a quantum memory; Step 3: After passing the security check, Alice extracts the photon sequence S. A The remaining photons are randomly selected. m For each photon, a random encoding operation is performed, and for the remaining photons... n Each photon is encoded with specific information according to the desired transmission information; after encoding, the photon sequence S is... A Send to Bob; Step 4: After Bob receives the photon sequence, he stores it in his memory, and Alice publishes the random code. m Charlie publishes the preparation basis for the entangled photon pairs at the positions of the photons, Bob extracts the corresponding photon pairs and performs Bell state measurements based on the preparation basis, and records the Bell state measurement results. Step 5: Alice publishes the encoding information of the random code; Charlie publishes the initial state at these positions. Bob performs a second round of security checks based on the Bell state measurement results and the information published by Alice and Charlie to ensure that there is no eavesdropping on the channel between him and Alice. Step 6: After passing the second round of security checks, Charlie announced the other locations, namely... n Bob extracted the corresponding photon pairs from the initial states of the entangled photon pairs and performed Bell state measurements on each entangled photon pair using the published preparation basis of the initial states. He then combined the initial state and Bell state measurement results to infer Alice's encoded information.

[0006] A controlled quantum-secure direct communication method based on multiple Bell basis sets is proposed. A third party prepares a series of entangled photon pairs, forming two photon sequences, which are sent to the communicating parties respectively. The communicating parties randomly select photons at the same positions in the sequences for single-photon measurements, performing the first round of security checks. After passing the first round, the sender selects a portion of photons in its sequence to encode and transmit the message, while the remaining photons are randomly encoded for the second round of security checks and sent to the receiver. The third party publishes the basis for preparing the entangled photon pairs, and the receiver performs Bell state measurements accordingly and records the results. The sender publishes the randomly encoded positions and encoding information, and the third party publishes the initial states at these positions. The receiver performs the second round of security checks; a bit error rate below a threshold indicates no eavesdropping. Finally, the third party publishes the initial states at the remaining positions, and the receiver infers the message to be transmitted by the sender based on the BSM measurement results. This method only requires Bell states for communication and only requires two rounds of transmission and two rounds of security checks, reducing the complexity of protocol implementation and improving communication efficiency.

[0007] The present invention has the following beneficial effects: (1) The controlled quantum secure direct communication scheme proposed in this invention only requires two rounds of transmission and two rounds of security detection, which can effectively reduce the consumption of quantum resources and improve communication efficiency.

[0008] (2) The controlled quantum secure direct communication scheme proposed in this invention only requires two sets of two-photon entanglement under Bell basis, which can reduce the requirements for preparing quantum states at the light source end and reduce the difficulty of implementing the protocol. Attached Figure Description

[0009] Figure 1 This is a flowchart of a controlled quantum-secure direct communication method based on multiple sets of Bell bases proposed in an embodiment of the present invention.

[0010] Figure 2 This is a schematic diagram of a controlled quantum-secure direct communication method based on multiple sets of Bell bases proposed in an embodiment of the present invention.

[0011] Figure 3 This is a diagram of a controlled quantum-secure direct communication system based on multiple sets of Bell bases designed in an embodiment of the present invention.

[0012] Figure 4 This is a schematic diagram illustrating the principle of Bell state measurement in an embodiment of the present invention. Detailed Implementation

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0014] As attached Figure 1 , Figure 2As shown, communication party A (information sender) is Alice, communication party B (information receiver) is Bob, and the third party (communication controller) is Charlie. This embodiment's specific quantum-safe direct communication implementation scheme includes the following steps: Step 1: Third-party Chalice preparation n + l + m Take entangled photon pairs, and then take one photon from each entangled photon pair to form an ordered photon sequence S. A Distribute the photons to Alice; form the remaining photons into a photon sequence S. B Distribute it to Bob.

[0015] The four entangled photon pairs are described as follows: ; ; Where H and V represent the horizontal and vertical polarization of the photons, respectively; the subscript X / Y indicates that the substrate is X / Y based; and the subscripts A / B indicate the photon sequence S to be emitted to Alice and Bob. A S B 'i' is the imaginary unit, representing the relative phase between quantum states. .

[0016] Step 2: After receiving the photon sequence, Alice randomly selects... l Single-photon measurements were performed using randomly selected photons as a basis for security detection, and the results in the photon sequence S were published. A Position and measurement results in the photon sequence S; Bob's measurement of the photon sequence S B The photons at the corresponding positions are randomly selected for basis measurement, and the measurement basis and measurement results are recorded for the first round of security checks; both parties store the remaining photons in the quantum memory.

[0017] In this method, single-photon measurements are performed using randomly selected bases, including... ; in Representing the diagonal basis and circular polarization basis under polarization degrees of freedom: ; ; in , These represent linear polarization states at 45° and 135°, respectively. , These represent right-handed and left-handed circularly polarized states, respectively; here, they are represented as the expansions of the orthogonal normalized basis vectors of the diagonal and circularly polarized bases in the X basis. When the measurement result is or When the result is 0, it is recorded as 0; when the measurement result is or When , it is recorded as 1.

[0018] The first round of security testing specifically involved Alice and Bob publishing the measurement basis and results, and Charlie publishing the initial state of the photon at the corresponding location. When the initial state was... ; Alice and Bob both chose the foundation for... Or all of them When the measurement results are both 0 or both are 1, the result is considered correct; otherwise, the result is discarded. When the initial state is ; Alice and Bob both chose the foundation for... Or all of them In this case, the measurement results are used to check safety; otherwise, the results are discarded. If Alice and Bob's measurement results are opposite, it is considered correct; if they are the same, it is considered incorrect. When the initial state is ; When Alice and Bob choose different bases, the measurement results are used to test safety; otherwise, the results are discarded. Details are as follows: (1) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are opposite, it is considered correct; if they are the same, it is considered incorrect. (2) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are both 0 or both are 1, it is considered correct; otherwise, it is considered incorrect. When the initial state is ; When Alice and Bob choose different bases, the measurement results are used to test safety; otherwise, the results are discarded. Details are as follows: (1) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are both 0 or 1, it is considered correct; otherwise, it is considered incorrect. (2) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are opposite, it is considered correct; if they are the same, it is considered incorrect. The total error rate is calculated based on the corresponding measurement results. If the error rate is below a certain threshold, the security test is considered to have passed.

[0019] Step 3: After passing the security check, Alice extracts sequence S from the quantum memory. A The remaining photons in the sample are randomly selected. m For each photon, a random encoding operation is performed, and for the remaining photons... n Each photon encodes specific information according to the desired transmission. After encoding, the sequence S is... A Send it to Bob.

[0020] Alice's random encoding operation and information encoding operation are specifically of two types: ; ; in This represents two encoding operations, corresponding to information 0 and 1 respectively; and These are the unit operator and the Pauli operator. Z When the encoding operation is random encoding, random selection is performed. Perform the operation; when the encoding operation is information encoding, Alice selects the corresponding 0 or 1 information to send. Record the corresponding location and operation.

[0021] Step 4: After Bob receives the photon, Alice publishes the random code. m Charlie publishes the preparation basis for the entangled photon pairs at the corresponding positions, and Bob extracts the corresponding photon pairs, performs unitary operations based on the preparation basis, and then performs Bell state measurements and records the measurement results.

[0022] Furthermore, in step 4, Bob's operation based on the preparation basis is as follows: if Charlie's preparation basis is X-based, Bob performs no operation; if Charlie's preparation basis is Y-based, Bob performs operations on the entangled photon pairs. operate: ; ; in It is a unitary operation used to modulate the phase of the polarization state, with the aim of introducing a phase difference into the vertical polarization component. This enables the conversion from circular polarization to linear polarization. It is a Pauli arithmetic operator Y; Then, Bell state measurements were performed; Bob used linear optical Bell state measurements to distinguish between different Bell states. .

[0023] Figure 4 is a schematic diagram of Bell state measurement in an embodiment of the present invention. PBS represents a polarization beam splitter, which can completely transmit photons polarized to H and completely reflect photons polarized to V. 1V / H D 2V / H These represent the vertical and horizontal single-photon detectors, respectively. Measurement results are recorded only if and only if both D1 and D2 respond simultaneously.

[0024] Step 5: Alice announces the location and encoding information of the random code; Charlie announces the initial state at these locations. Bob performs a second round of security checks based on the BSM results and the information announced by Alice and Charlie to ensure that there is no eavesdropping on the channel between him and Alice.

[0025] Specifically, the second round of security testing uses BSM (Browser-Sensitive Model). For entangled photon pairs at the same location, Bob's measurement results and Charlie's published initial state have two possibilities: either they are identical, indicating that the measured random operation is... If it matches the random operation information published by Alice, it indicates correctness; otherwise, it is marked as incorrect. One reason is that the two only have opposite signs, indicating that the measured random operation is... If it matches the random operation information published by Alice, it indicates that it is correct; otherwise, it is marked as incorrect.

[0026] The total error rate can be calculated based on the corresponding measurements. If the error rate is below a certain threshold, the second round of security testing is considered to have passed, indicating that the quantum communication channel between Alice and Bob is free from eavesdropping.

[0027] Step 6: After passing the second round of security checks, Charlie announced the other locations, namely... n Bob extracted the initial states of each entangled photon pair and performed Bell state measurements on each pair using the published preparation basis of the initial states. By combining the initial state and Bell state measurement results, Alice's encoded information can be deduced.

[0028] Example 1: During the communication process, assuming that in the first round of security detection, for l If Charlie publishes the initial state of a given position on two entangled photons at the same location, then... Alice and Bob both used the measurement basis X basis. If they both obtain the same single-photon measurement result, it is considered correct. Alice and Bob each use a security detection photon pair, calculate the error rate, and proceed to the next step if it is below a threshold. Then, in...m In the entangled photon pair used for the second round of security testing, the initial state is given. For example, if Alice performs random operations on the single photon in her hand... After being sent to Bob, it forms an entangled state with the corresponding single photon in his hand. Measured by BSM According to the initial state released by a third party From this, we can deduce that Alice performs random operation 1 on this photon pair. Similarly, Alice measures these m security detection photon pairs, calculates the error rate, and if the error rate is below a threshold, proceeds to the next step. Finally, in the actual process of transmitting the ciphertext... n In a pair of entangled photons, if Charlie prepares the initial state as follows: Alice wants to transmit the information "1" by processing the photons in her hand. After the operation, it is sent to Bob. At this point, the entangled state is... Since the basis for preparing its entangled state is Y, Bob needs to first process the photons sent by Alice. Operations that make it a distinguishable Bell state. By comparing the initial state at the corresponding position with that published by Charlie, it can be deduced that the bit information Alice actually wants to send is "1".

[0029] Example 2: Figure 3 As shown, this embodiment of the invention also provides a quantum-safe direct communication system, including an information receiver Bob, an information sender Alice, and a communication controller Charlie. The communication method is described in [reference needed]. Figure 1 The communication controller prepares a large number of four entangled states. One photon is extracted from each entangled state to form a photon sequence, which is sent to the information sender. The remaining photons are sent sequentially to the information receiver. The sender and receiver perform single-photon measurements at designated, identical locations and conduct a first-round security check based on the initial state published by the controller. After passing the security check, the sender encodes the remaining photon sequence and performs random operations for a second-round security check, then sends the sequence to the receiver. The receiver performs a second-round security check using Bell state measurements on the photons in their hand. After passing the security check, the receiver decodes the sequence to obtain the information sent by the sender. The specific methods and steps employed are detailed in Example 1 and will not be repeated here for brevity.

[0030] The above description is only a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present invention should be included within the scope of protection set forth in the claims.

Claims

1. A controlled quantum-secure direct communication method based on multiple sets of Bell bases, characterized in that, Includes the following steps: Step 1: Third-party Chalice preparation n + l + m Take entangled photon pairs, and then take one photon from each entangled photon pair to form an ordered photon sequence S. A Distribute the photons to Alice; form the remaining photons into a photon sequence S. B Distribute it to Bob; Step 2: After receiving the photon sequence, Alice randomly selects... l Single-photon measurements were performed using randomly selected photons as a basis for security detection, and the results in the photon sequence S were published. A Position and measurement results in the photon sequence S; Bob's measurement of the photon sequence S B The photons at the corresponding positions are randomly selected for basis measurement, and the measurement basis and measurement results are recorded for the first round of security checks; both parties store the remaining photons in a quantum memory; Step 3: After passing the security check, Alice extracts the photon sequence S. A The remaining photons are randomly selected. m For each photon, a random encoding operation is performed, and for the remaining photons... n Each photon is encoded with specific information according to the desired transmission information; after encoding, the photon sequence S is... A Send to Bob; Step 4: After Bob receives the photon sequence, he stores it in his memory, and Alice publishes the random code. m Charlie publishes the preparation basis for the entangled photon pairs at the positions of the photons, Bob extracts the corresponding photon pairs and performs Bell state measurements based on the preparation basis, and records the Bell state measurement results. Step 5: Alice publishes the encoding information of the random code; Charlie publishes the initial state at these positions. Bob performs a second round of security checks based on the Bell state measurement results and the information published by Alice and Charlie to ensure that there is no eavesdropping on the channel between him and Alice. Step 6: After passing the second round of security checks, Charlie announced the other locations, namely... n Bob extracted the corresponding photon pairs from the initial states of the entangled photon pairs and performed Bell state measurements on each entangled photon pair using the published preparation basis of the initial states. He then combined the initial state and Bell state measurement results to infer Alice's encoded information.

2. The controlled quantum-secure direct communication method based on multiple sets of Bell bases according to claim 1, characterized in that: The four entangled photon pairs mentioned in step 1 are described as follows: ； ； Where H and V represent the horizontal and vertical polarization of the photons, respectively; the subscript X / Y indicates that the substrate is X / Y based; and the subscripts A / B indicate the photon sequence S to be emitted to Alice and Bob. A S B 'i' is the imaginary unit, representing the relative phase between quantum states. .

3. The controlled quantum-secure direct communication method based on multiple sets of Bell bases according to claim 2, characterized in that: In step 2, Alice and Bob randomly select l photons at the same position from the received photon sequence to perform single-photon measurements; wherein the single-photon measurements are performed by randomly selecting a basis, and the randomly selected basis includes ； in Representing the diagonal basis and circular polarization basis under polarization degrees of freedom: ； ； in , These represent linear polarization states at 45° and 135°, respectively. , These represent right-handed and left-handed circularly polarized states, respectively; here, they are represented as the expansions of the orthogonal normalized basis vectors of the diagonal and circularly polarized bases in the X basis. When the measurement result is or When the result is 0, it is recorded as 0; when the measurement result is or When the time is 1, it is recorded as 1.

4. The controlled quantum-secure direct communication method based on multiple sets of Bell bases according to claim 3, characterized in that: In step 2, the first round of security checks specifically involves Alice and Bob announcing the measurement basis and results, and Charlie announcing the initial state of the photon at the corresponding location. When the initial state is... ； Alice and Bob both chose the foundation for... Or all of them When the measurement results are both 0 or both are 1, the result is considered correct; otherwise, the result is discarded. When the initial state is ； Alice and Bob both chose the foundation for... Or all of them In this case, the measurement results are used to check safety; otherwise, the results are discarded. If Alice and Bob's measurement results are opposite, it is considered correct; if they are the same, it is considered incorrect. When the initial state is ； When Alice and Bob choose different bases, the measurement results are used to test safety; otherwise, the results are discarded. Details are as follows: (1) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are opposite, it is considered correct; if they are the same, it is considered incorrect. (2) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are both 0 or both are 1, it is considered correct; otherwise, it is considered incorrect. When the initial state is ； When Alice and Bob choose different bases, the measurement results are used to test safety; otherwise, the results are discarded. Details are as follows: (1) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are both 0 or 1, it is considered correct; otherwise, it is considered incorrect. (2) Alice chooses Bob chose When measuring the baseline, if Alice and Bob's measurement results are opposite, it is considered correct; if they are the same, it is considered incorrect. The total error rate is calculated based on the corresponding measurement results. If the error rate is below a certain threshold, the security test is considered to have passed.

5. A controlled quantum-secure direct communication method based on multiple sets of Bell bases according to claim 4, characterized in that: Step 3 specifically involves Alice's random encoding operation and information encoding operation, which include: ； ； in This represents two encoding operations, corresponding to information 0 and 1 respectively; and These are the unit operator and the Pauli operator. Z When the encoding operation is random encoding, random selection is performed. Perform the operation; when the encoding operation is information encoding, Alice selects the corresponding 0 or 1 information to send. Record the corresponding location and operation.

6. The controlled quantum-secure direct communication method based on multiple sets of Bell bases according to claim 5, characterized in that: In step 4, Bob's operation of performing Bell state measurements based on basis selection is as follows: if Charlie's preparation basis is X-based, Bob directly performs Bell state measurements; if Charlie's preparation basis is Y-based, Bob first performs a unitary operation on the photon pair, specifically: ； in It is a unitary operation used to modulate the phase of the polarization state, with the aim of introducing a phase difference into the vertical polarization component. This enables the conversion from circular polarization to linear polarization. It is a Pauli arithmetic operator Y ; Then Bell state measurements were performed; Bob used linear optical Bell state measurements to distinguish between them. .

7. A controlled quantum-secure direct communication method based on multiple sets of Bell bases according to claim 6, characterized in that: In step 5, the second round of security testing specifically involves Bob inferring Alice's random coding operation based on the Bell state measurement results and the initial state published by Charlie, and comparing it with the results published by Alice.

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