Controlled semi-quantum dialogue method and system based on Bell state

Abstract

The invention discloses a controlled semi-quantum dialogue method and system based on semi-quantum cryptography and an entangled Bell state. Wherein a manager Charlie prepares a large number of entangled photon pairs, and splits the photon pair in each entangled state into a coding sequence and a test sequence. Only under the condition that the channel is ensured to be safe, the quantum communication party Alice and the classic communication party Bob can code in the sequence in sequence, and finally the code is returned to the management party Charlie for measurement to complete communication. According to the method, the quantum communication party and the classical communication party can exchange secret information at the same time under the supervision of the management party Charlie, that is, only through the permission of the management party Charlie. In addition, compared with a one-way semi-quantum communication protocol, the communication efficiency is remarkably improved by introducing a dialogue mechanism. Compared with a complex GHZ state, the Bell state adopted by the invention is simpler and more convenient in preparation, so that the implementation difficulty is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of quantum cryptography, and particularly relates to a controlled semi-quantum conversation method and system based on Bell states. BACKGROUND

[0002] Quantum communication is a communication method based on the principles of quantum mechanics, which uses the states of quantum bits (qubits) to encode information and transmits it through quantum channels. The most famous form of quantum communication is the quantum key distribution (QKD) scheme proposed in 1984, which allows two communicating parties to securely share an encryption key that can then be used to encrypt and decrypt messages. Due to the measurement collapse property in quantum mechanics, any unauthorized measurement on a quantum state will change its state, which makes it impossible for an eavesdropper to intercept information without being detected. Therefore, quantum communication provides theoretically unbreakable security. Previous quantum cryptography schemes usually assume that both communicating parties have advanced quantum technology and can perform operations such as preparing, storing, and measuring quantum states. However, in practical application scenarios, such requirements may be difficult to achieve. Since quantum devices are not only expensive but also large and not easy to carry, not every participant can easily obtain or use these resources.

[0003] In order to be closer to actual needs, researchers have explored more flexible methods that allow some communicating parties to have limited quantum capabilities or even rely entirely on classical technology. This way not only lowers the threshold for communication, but also allows more users to benefit from the security features of quantum cryptography, while avoiding strict technical requirements for all participants. Through this compromise strategy, the practicality and accessibility of quantum communication systems can be improved without sacrificing security. In recent years, researchers have designed a semi-quantum key distribution (SQKD) scheme, which makes it possible to establish a key between a quantum communication body and a classical communication body. In this scheme, no Z-basis superposition state is involved. Instead, the classical communication party is limited to the following operations: (1) can only measure and prepare quantum bits with Z-basis ; (2) can reflect quantum bits without any interference; (3) can reorder quantum bits through different delay lines.

[0004] However, research on semi-quantum bidirectional communication, also known as semi-quantum dialogue, where the communicating parties simultaneously exchange secrets, is not widespread. In 2017, a Bell state-based SQD scheme was first proposed, where the classical communicating parties XOR the measurement result with the secret message to encrypt the secret message, achieving secure and efficient dialogue. In 2018, two methods using single photons for semi-quantum dialogue were first proposed; single photons are easier to prepare than Bell states. In 2020, based on the correlation of entangled Bell particles, an SQD scheme to prevent information leakage was proposed. However, in 2023, a security vulnerability was discovered in the above scheme. An eavesdropper, Eve, could use a dual-control no-operation attack to obtain Bob's secrets undetected. Finally, the semi-quantum dialogue protocol was improved, and its security was proven. In 2021, a three-party semi-quantum scheme for deterministic secure quantum dialogue based on GHZ states was proposed, extending semi-quantum dialogue from two parties to three parties. Furthermore, the innovative scheme for realizing semi-quantum dialogue using super-entangled Bell states, first proposed in 2023, elevates this technology to a new milestone. This novel approach marks a significant breakthrough in the field of semi-quantum communication.

[0005] Despite numerous innovations and advancements in the field of semi-quantum dialogue, no researchers have yet proposed a solution specifically for the concept of "controlled" communication. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a controlled semi-quantum dialogue method and system based on Bell states, which solves the problem of the lack of semi-quantum controlled concepts and specific solutions in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A controlled semi-quantum dialogue method based on Bell states includes the following steps:

[0009] Step 1, Management by Charlie Bell state particles To form a sequence of all A particles All B particles are composed of and will Sent to Alice, the quantum communication provider. Retain, among which, This represents the number of bits in the secret message exchanged between Alice, the quantum communicator, and Bob, the classical communicator. These represent the number of bait particles required for three safety checks;

[0010] Step 2: When Alice, the quantum communication party, receives the sequence Then, in the sequence Random selection These particles, used as decoy particles for the first security check, are denoted as sequence. Then, in cooperation with the management Charlie, a first security test is conducted. If the error rate is lower than the set threshold, step 3 is continued; otherwise, the communication is terminated.

[0011] Step 3: Alice, the quantum communication partner, will send the sequence... Remove, and according to the secret information you want to transmit. Randomly select one of them Each particle performs a unitary operation. Encode the sequence, denoted as the encoded sequence. Then Randomly selected from the sequence These particles, used as decoy particles for the second security check, are denoted as sequence. And randomly insert it into the encoded sequence Forming a sequence Finally, the sequence Send to Bob, the classic communicator;

[0012] Step 4: Bob, the classic communicator, receives the sequence. Subsequently, Alice, the quantum communication expert, announced the decoy particle sequence. In classic communication, Bob directly transmits the sequence The error is reflected back to the administrator Charlie, who performs a second security check by executing Bell base measurements. If the error rate is within a safe range, it is determined that there is no eavesdropper.

[0013] Step 5: Bob, the classic communicator, transmits the secret message... , for those containing A sequence of qubits Two classical operations are performed for encoding, and the particles after the two encodings are denoted as a sequence. Then the rest A sequence of decoy particles With the particle sequence after two encodings Using the permutation operator Reorder to form a sequence Finally, the sequence Send to administrator Charlie;

[0014] Step 6: Charlie, the administrator, receives the sequence. Subsequently, Bob, the classical communicator, announced the decoy particle sequence. the correct order of arrangement, the manager Charlie measures with Bell base, if the result is the same as the initial state, it is determined that the process has no eavesdropper, continue to step 7, otherwise terminate the communication;

[0015] Step 7, the classical communication party Bob discloses the correct order of arrangement of the encoded sequence , the manager Charlie measures with Z base after recovery, and announces the measurement result and the initial state, and the quantum communication party Alice and the classical communication party Bob infer the secret message of the other party according to the measurement result and the initial state.

[0016] In step 1, is in one of the following four states:

[0017] ;

[0018] ;

[0019] wherein, is the Dirac symbol, indicating the right arrow.

[0020] In step 2, the quantum communication party Alice randomly selects quantum bits as the decoy particle sequence , and measures with Z base or X base; then, the positions of the decoy particle sequence and the measurement base are disclosed, the manager Charlie measures at the corresponding positions according to the known information, and sends the measurement result to Alice, and the quantum communication party Alice judges whether there is eavesdropping by comparing the results, if it is safe, it is determined that there is no eavesdropper in the channel between the manager Charlie and the quantum communication party Alice, and the process continues, otherwise it is immediately terminated.

[0021] In step 3, the unitary operation includes Pauli , operation, the quantum communication party Alice performs the following two operations according to the secret information to be transmitted by herself:

[0022] (1) If , the quantum communication party Alice performs Pauli operation on A particle, the state of the system remains unchanged;

[0023] (2) If , the quantum communication party Alice performs Pauli operation on A particle, the state of the system becomes:

[0024]

[0025] After the operation, the sequence is recorded as the encoded sequence The quantum correspondent Alice randomly selects particles to act as decoy particles for the second security check, and the sequence is recorded as The sequence is randomly inserted into the encoded sequence After , it is sent to the classical correspondent Bob.

[0026] In step 4, first, the quantum correspondent Alice publishes The position of the decoy particle sequence in Bob directly reflects the sequence to the management Charlie, and the management Charlie finds the sequence corresponding to the sequence in the sequence ; Then, the management Charlie measures the sequence and the sequence with the Bell basis, and if the measurement result is the same as the initial state, it is determined that there is no eavesdropper in the channel between the quantum correspondent Alice and the classical correspondent Bob, otherwise it is immediately terminated.

[0027] In step 5, on the premise that the channel is proved to be secure, the classical correspondent Bob performs two classical operations on the sequence containing quantum bits to encode:

[0028] (1) If , Bob performs CTRL mode, i.e. reflects the quantum bits to the management Charlie without any interference;

[0029] (2) If , SIFT mode is executed, specifically as follows: The classical correspondent Bob measures the A particles with the Z basis, and if the measurement result is the quantum state , a quantum state is prepared; Similarly, if the quantum state is obtained, the quantum state is prepared. After performing the measurement and preparing the quantum state operation, the encoded particles are recorded as the sequence , and the remaining decoy particle sequence and the encoded particle sequence are reordered using the permutation operator to form , and finally the sequence is sent to the management Charlie.

[0030] In step 5, the permutation operator is defined as an operator acting on a multi-qubit system that rearranges the order of qubits according to a given rule or pattern; the permutation operator is represented as a matrix that acts on vectors in Hilbert space, and for a system of qubits, this matrix will be of size Each permutation corresponds to a specific permutation matrix,

[0031] For any number of qubits and any specific permutation pattern, the corresponding permutation matrix is constructed, and each matrix element represents the probability amplitude of transitioning from the th ground state to the th ground state, in the case of a permutation operator, each row and each column has exactly one non-zero element equal to 1, and the rest are 0, this process changes the relative positions between qubits, but does not change the state of the individual qubits themselves.

[0032] In step 7, if the management party Charlie allows the quantum communication party Alice and the classical communication party Bob to communicate, the measurement results and initial states are announced, otherwise the quantum communication party Alice and the classical communication party Bob cannot obtain each other's secret messages; the quantum communication party Alice and the classical communication party Bob infer the secret messages of the other party according to the measurement results announced by the management party Charlie and the operations performed by each party.

[0033] The management party Charlie and the quantum communication party Alice are trusted and have complete quantum capabilities, and the classical communication party Bob is limited in capability and can only perform limited quantum operations.

[0034] The controlled semi-quantum dialogue system based on Bell states sets a photon number distributor and a wavelength filter in front of the devices of the quantum communication party Alice and the classical communication party Bob, which is used to resist Trojan horse attacks.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] 1、The present application first introduces a controlled semi-quantum dialogue method (CSQD), which uses a controlled mechanism, and the dialogue is "controlled", which means that there is a trusted management party to control the dialogue process. This increases the flexibility of the system, allowing more complex access structures and permission management, while also providing additional security against illegal intervention, opening up new directions in this field.

[0037] 2、By introducing a trusted manager, it is ensured that only with the authorization of the manager, the two parties can exchange information. The proposed method contains quantum information that cannot be accurately copied, i.e. the quantum no-cloning theorem, and any attempt to eavesdrop or tamper with the message will leave a trace, which can be detected by the legitimate user, greatly enhancing the security. The present application greatly increases the security of the system by adding a trusted third-party manager, such as Charlie, who needs to obtain his permission before each conversation, which greatly increases the security of the system. Any unauthorized attempt will be immediately detected and prevented.

[0038] 3、Compared with the one-way semi-quantum communication protocol, the present application significantly improves the communication efficiency by introducing a conversation mechanism. Compared with the complex GHZ state, the Bell state used in the present application is simpler to prepare, thereby reducing the implementation difficulty.

[0039] 4、By using the characteristics of semi-quantum, not all participants need to have the ability to fully operate quantum information. Some users only need to be able to prepare, measure specific quantum states, or perform simple single-qubit operations to participate in the conversation. This greatly reduces the quantum device requirements for end users, making more users able to use this technology.

[0040] 5、The controlled semi-quantum conversation method proposed in the present application is suitable for communication scenarios that require high security, such as the exchange of sensitive information in financial transactions. BRIEF DESCRIPTION OF DRAWINGS

[0041] Fig. 1 The communication flow diagram of the controlled semi-quantum conversation method based on Bell state of the present application.

[0042] Fig. 2 The initial state of the system of the present application is When the initial state of the system of the present application is

[0043] Fig. 3 The initial state of the system of the present application is When the initial state of the system of the present application is DETAILED DESCRIPTION

[0044] The structure and working process of the present application will be further described below with reference to the accompanying drawings.

[0045] The present application designs a controlled semi-quantum conversation method based on Bell state, which realizes the two-way communication of quantum parties and classical parties under the control of the manager. The controlled semi-quantum conversation method based on Bell state includes the following seven processes:

[0046] Step 1: The manager Charlie prepares Bell state particles , are in one of the following four states:

[0047] ;

[0048] ;

[0049] where, is the Dirac notation, representing the right vector; represents the number of bits of the secret messages that quantum correspondent Alice and classical correspondent Bob want to exchange with each other, respectively represent the number of decoy particles needed for the three security checks. Subsequently, the supervisor Charlie picks out all the A particles to form the sequence , and picks out all the B particles to form the sequence . Finally, is sent to the quantum correspondent Alice, is kept in the hand of the supervisor.

[0050] Step 2: After the quantum correspondent Alice receives the sequence , she randomly picks particles in the sequence to act as decoy particles for the first security check, denoted as the sequence , and measures them in the Z basis or the X basis. The Z basis and the X basis are respectively denoted as:

[0051] ;

[0052] ;

[0053] Subsequently, the quantum correspondent Alice discloses the positions of the decoy particle sequence , as well as the measurement basis. The supervisor Charlie measures in the corresponding positions according to the known information, and sends the measurement results to the quantum correspondent Alice. Due to the characteristics of Bell state entanglement, the measurement results are correlated. The quantum correspondent Alice can judge whether there is eavesdropping by comparing the results. If it is safe, it proves that there is no eavesdropper in the channel between the supervisor Charlie and the quantum correspondent Alice, and the next step is continued; otherwise, the communication is terminated.

[0054] Step 3: After the quantum correspondent Alice removes the decoy particle sequence , she randomly picks particles and performs the following two unitary operations according to the secret information she wants to transmit respectively:

[0055] (1) If , quantum correspondent Alice will perform a Pauli operation on particle A, and the state of the system remains unchanged;

[0056] (2) If , quantum correspondent Alice will perform a Pauli operation on particle A, and the state of the system will change to:

[0057] ; where the Pauli , operations are represented as:

[0058] , ;

[0059] , .

[0060] After encoding, it is denoted as the encoding sequence . Quantum correspondent Alice randomly selects particles to act as decoy particles for the second security check, denoted as the sequence . After randomly inserting them into the encoding sequence to form , it is sent to classical correspondent Bob.

[0061] Step 4: After receiving the sequence , quantum correspondent Alice publishes the positions of the decoy particle sequence in the sequence , and Bob directly reflects the sequence to the management Charlie. Management Charlie finds the sequence corresponding to the sequence in the sequence ; then, management Charlie measures the sequence and the sequence using Bell basis, if the measurement result obtained is the same as the initial state, it is determined that there is no eavesdropper in the channel between quantum correspondent Alice and classical correspondent Bob, otherwise it is immediately terminated.

[0062] Step 5: On the premise that the channel is proved to be secure, classical correspondent Bob performs two classical operations on the sequence containing quantum bits to encode:

[0063] (1) If ,If so, Bob will execute CTRL mode, which means he will reflect the qubits back to the administrator Charlie without any interference.

[0064] (2) If Then the SIFT mode is executed, which is explained as follows: In classical communication, Bob uses the Z basis to measure particle A. If the measurement result is a quantum state... Then an opposite quantum state is prepared. Similarly, if a quantum state is obtained... Regarding the preparation of quantum states Then the encoded particles are recorded as a sequence. And put the rest A sequence of decoy particles With the encoded particle sequence Using the permutation operator Reordering And record their order. Each permutation corresponds to a specific permutation matrix. Consider a simple example with 3 qubits. To swap the positions of the first and third qubits, we can define a permutation operator. , making The corresponding permutation matrix It will be like this matrix:

[0065]

[0066] For any number For any given qubit and any specific permutation mode, a corresponding permutation matrix can be constructed using the method described above. Each matrix element... Indicates from the first The ground state transitions to the... The probability amplitude of each ground state. In the case of the permutation operator, because it is a deterministic operation, each row and each column has exactly one non-zero element equal to 1, and the rest are 0. This process changes the relative positions between qubits, but does not change the state of the individual qubits themselves. Finally, The sequence is sent to the administrator, Charlie.

[0067] Step 6: Charlie, the manager, received... Afterwards, Bob, the classical communicator, will announce the decoy particle sequence. The correct order. After Charlie, the administrator, restored the order, it was in the sequence. Find the sequence Corresponding sequence Then, Charlie, the administrator, used the Bell basis to measure the sequence. and sequence If the result is the same as the initial state, it proves that there is no eavesdropper in the process. Because the quantum correspondent Alice and the classical correspondent Bob have not measured the quantum bits in sequence at all during the whole process, but simply reflected them, the quantum bits in sequence and sequence still have the entanglement property. In the case of no eavesdropper, the measurement with Bell basis will get the same result as the initial state, and the next step will be continued. If the measurement result is different from the initial state, it will be terminated immediately.

[0068] Step 7: The classical correspondent Bob discloses the correct arrangement order of the encoded sequence , and the manager Charlie recovers the correct sequence and measures sequence and sequence with Z basis. If the manager Charlie allows the quantum correspondent Alice and the classical correspondent Bob to communicate, the measurement result and the initial state are announced. Otherwise, the quantum correspondent Alice and the classical correspondent Bob cannot obtain the secret message of the other party. According to the measurement result announced by the manager Charlie and the operation performed by each of them, the quantum correspondent Alice and the classical correspondent Bob can infer the secret message of the other party. And in the whole process, the third party manager cannot obtain any message of the participants.

[0069] The present scheme involves three participants, among which the trusted manager Charlie and the quantum correspondent Alice have complete quantum ability, and the other participant Bob is limited in ability, i.e. the classical correspondent can only perform the following limited operations:

[0070] (1) can only measure and prepare quantum bits with Z basis ;

[0071] (2) can reflect quantum bits to the manager Charlie without any disturbance;

[0072] (3) can reorder quantum bits through different delay lines.

[0073] Specific embodiments, as shown in Figs. 1 to 3 :

[0074] Fig. 2 and Fig. 3 respectively represent that when the initial state is , , the relationship between the measurement result of the manager Charlie and the secret information of the two communicators, and the process of the present application will be analyzed in combination with specific examples as follows:

[0075] The initial state prepared by the manager Charlie is At the start of communication, neither Alice, the quantum communicator, nor Bob, the classical communicator, knows the initial state. Charlie only reveals the initial state in the final step, when she allows them to communicate. The secret information that Alice, the quantum communicator, wants to transmit... The secret information that Bob, the classic communicator, wants to transmit. Therefore, Alice, the quantum communication provider, receives... In Particles perform unitary operations The system state remains unchanged. In classic communication, Bob receives... In Particles perform SIFT mode, i.e., measurements using Z-basis. The particle then sends the opposite quantum state to Charlie.

[0076] Here we need to note that in the classic communication method, Bob... When the particles are measured, the system is in an entangled Bell state, therefore a Z-basis is used for measurement. Particles, the state of the system collapses into , The probability of each is 1 / 2.

[0077] Therefore, let's assume it collapses into... (collapsed into) (The situation is similar.) After the measurement is completed, Bob, the classical communicator, executes the SIFT mode, which will then transmit the newly prepared quantum state. opposite quantum states Send to administrator Charlie. Administrator Charlie uses the Z-base to measure. In Particles and In The particles will get If the administrator Charlie allows the quantum communication agent Alice and the classical communication agent Bob to communicate, she will publicly announce the final measurement results and the initial Bell state. Therefore, based on her own actions and the measurement results announced by Charlie, the quantum communication agent Alice infers that the classical communication agent Bob is executing a SIFT mode, i.e., she derives... Similarly, Bob, the classical communicator, can deduce that Alice, the quantum communicator, is performing [the following action / function]. This operation allows them to obtain Alice's secret information through quantum communication. Only when the permission of the manager Charlie is obtained, the secret messages of the two parties can be obtained, and the two-way real-time semi-quantum communication, i.e. controlled two-way semi-quantum conversation, is realized.

[0078] The scheme also discloses a conversation system of the controlled semi-quantum conversation method based on Bell states. In order to avoid Trojan horse attacks, the quantum communication party Alice and the classical communication party Bob can place a photon number splitter (PNS) and a wavelength filter in front of their devices to resist such attacks.

[0079] It should be understood that the scheme is not limited to the specific embodiments described above, and the devices and structures not described in detail should be understood as being implemented in the ordinary way in the art; any person skilled in the art can make many possible changes and modifications to the technical solutions of the scheme or modify them into equivalent embodiments with equivalent changes without departing from the scope of the technical solutions of the scheme, which does not affect the essential content of the scheme. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the scheme without departing from the content of the technical solutions of the scheme still belongs to the protection scope of the technical solutions of the scheme.

Claims

1. A method of controlled semi-quantum conversation based on Bell states, characterized in that, The method comprises the following steps: Step 1, the manager Charlie prepares a Bell state particle , all A particles form a sequence , all B particles form , and sends to the quantum communication party Alice, retains, wherein, represents the number of bits of secret messages exchanged between the quantum communication party Alice and the classical communication party Bob, respectively represent the number of decoy particles required for three security checks; Step 2: When Alice, the quantum communication party, receives the sequence Then, in the sequence Random selection These particles, used as decoy particles for the first security check, are denoted as sequence. Then, in cooperation with the management Charlie, a first security test is conducted. If the error rate is lower than the set threshold, step 3 is continued; otherwise, the communication is terminated. Step 3, quantum correspondent Alice removes the sequence and encodes it according to the secret information she wants to transmit Randomly pairs the particles in the sequence and performs a unitary operation on each pair The encoding is performed, and the encoded sequence is denoted by Then, randomly selects particles from the sequence as decoy particles for a second security check, denoted by the sequence and randomly inserts them into the encoded sequence to form the sequence Finally, sends the sequence to classical correspondent Bob; Step 4, classical communication party Bob receives the sequence Afterwards, quantum communication party Alice announces the decoy particle sequence , and classical communication party Bob directly reflects the sequence to management party Charlie, and management party Charlie performs a second security check by performing Bell base measurement, and if the error rate is within the safe range, it is determined that there is no eavesdropper; Step 5. Classical communicator Bob encodes the secret message to be transmitted , and sends the sequence to the quantum communicator Alice. Step 6. Alice performs two classical operations to encode the secret message, and the sequence is sent to the quantum communicator Bob. Step 7. Bob performs two classical operations to encode the secret message, and the sequence is sent to the quantum communicator Charlie. Step 8. Charlie performs two classical operations to encode the secret message, and the sequence is sent to the quantum communicator Alice. Step 9. Alice performs two classical operations to encode the secret message, and the sequence is sent to the quantum communicator Bob. Step 6, the manager Charlie receives the sequence After that, the classical communicator Bob announces the correct order of the sequence of the decoy particles, the manager Charlie measures with Bell bases, if the result is the same as the initial state, it is determined that there is no eavesdropper in the process, and step 7 is continued, otherwise the communication is terminated. ​ Step 7, the classical communication party Bob discloses the correct arrangement order of the encoding sequence of the quantum communication party Alice, the quantum communication party Alice and the classical communication party Bob infer the secret message of each other according to the measurement result and the initial state.

2. The Bell state based controlled semi-quantum session method of claim 1, wherein: In step 1, one of the following four states: ； ； wherein is the Dirac notation for the right vector.

3. The Bell-state-based controlled semi-quantum session method of claim 1, wherein: In step 2, Alice, the quantum communication partner, will randomly select... One qubit, as a sequence of decoy particles And measurements were performed using Z-based or X-based methods; subsequently, the decoy particle sequence was... The location and measurement base are made public. The administrator, Charlie, performs measurements at the corresponding location based on the known information and sends the measurement results to Alice. Alice, the quantum communication provider, compares the results to determine whether there is any eavesdropping. If it is safe, it is determined that there is no eavesdropper in the channel between Charlie and Alice, and the process continues; otherwise, it terminates immediately.

4. The Bell-state-based controlled semi-quantum session method of claim 1, wherein: In Step 3, the unitary operation includes a Pauli , operation, and quantum correspondent Alice performs the following two operations according to the secret information she wants to transmit , respectively. (1) If , quantum communication party Alice performs the Pauli operation on the A particle, the state of the system remains unchanged; (2) If , the quantum communication party Alice performs the Pauli operation on the A particle, and the state of the system becomes: After the operation is completed, record the encoding sequence , the quantum communication party Alice randomly selects particles to act as decoy particles for the second security check, recorded as the sequence , randomly inserted into the encoding sequence form After that, send to the classical communication party Bob.

5. The Bell state based controlled semi-quantum session method of claim 1, wherein: In step 4, firstly, Alice, the quantum communication provider, announced... Middle decoy particle sequence Position, Bob will sequence The message is reflected directly to the administrator Charlie, who then processes it in the sequence. Find the sequence Corresponding sequence Then, Charlie, the administrator, used the Bell basis to measure the sequence. and sequence If the measurement result is the same as the initial state, it is determined that there is no eavesdropper in the channel between the quantum communication party Alice and the classical communication party Bob; otherwise, the process terminates immediately.

6. The Bell state based controlled semi-quantum session method of claim 1, wherein: In step 5, under the assumption that the quantum channel is secure, the classical party Bob encodes the sequence of qubits containing the secret key by performing two classical operations: (1) If Bob performs the CTRL mode, i.e. reflects the qubit to the manager Charlie without any disturbance; (2) If , then the SIFT mode is executed, specifically as follows: the classical communication party Bob measures the A particle with the Z basis, and if the measurement result is the quantum state , then a reverse quantum state is prepared; Similarly, if a quantum state is obtained Regarding the preparation of quantum states After performing the measurement and preparation of the quantum state, the encoded particles are recorded as a sequence. and put the rest A sequence of decoy particles With the encoded particle sequence Using the permutation operator Reordering Finally The sequence is sent to the administrator, Charlie.

7. The Bell state based controlled semi-quantum session method of claim 1, wherein: In step 5, the permutation operator is defined as an operator acting on a multi-qubit system that rearranges the order of the qubits according to a given rule or pattern; the permutation operator is represented as a matrix that acts on vectors in the Hilbert space, and for a system of qubits, this matrix will be of size Each permutation corresponds to a specific permutation matrix, For any number of qubits, and any particular permutation pattern, a corresponding permutation matrix is constructed, each matrix element represents the probability amplitude of transitioning from the th ground state to the th ground state. In the case of a permutation operator, there is exactly one non-zero element per row and per column, which is equal to 1, and the rest are 0. This process changes the relative positions between the qubits, but not the state of the individual qubits themselves.

8. The Bell state based controlled semi-quantum session method of claim 1, wherein: In step 7, if the management party Charlie allows the quantum communication party Alice and the classical communication party Bob to communicate, the measurement result and the initial state are declared, otherwise the quantum communication party Alice and the classical communication party Bob cannot obtain the secret message of the other party; the quantum communication party Alice and the classical communication party Bob infer the secret message of the other party according to the measurement result declared by the management party Charlie and the operation performed by each party. 9.The Bell-state-based controlled semi-quantum session method according to claim 1, wherein: The management party Charlie and the quantum communication party Alice are trusted and have complete quantum ability, and the classical communication party Bob is limited in ability and can only perform limited quantum operation.

10. A conversation system based on the Bell state based controlled semi-quantum conversation method according to any one of claims 1 to 9, characterized in that: A photon number distributor and a wavelength filter are arranged in front of the equipment of the quantum communication party Alice and the classical communication party Bob, so as to resist Trojan horse attack.

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