Quantum secure direct communication method based on quantum walk

Abstract

The application discloses a quantum secure direct communication method based on quantum walk, which comprises the following steps: encoding an initial state of a quantum walk system; performing one-step quantum walk based on a directed ring graph to obtain a shared entangled state; re-describing a quantum channel shared by a sender and a receiver; the sender performs measurement based on a position-based measurement basis and sends the measurement result to the receiver; the receiver performs corresponding measurement based on a coin-based measurement basis; the sender and the receiver compare measurement results to realize channel judgment; a composite quantum state is calculated; the second-step quantum walk based on the directed ring graph is performed to obtain a final quantum entangled state; the sender performs projection measurement and transmits the receiver; the receiver performs measurement and acquires secret information, thereby completing the quantum secure direct communication based on the quantum walk. The application avoids the advance preparation of the entangled state, avoids the security risk in particle distribution, has higher measurement efficiency and is easier to realize in experiments, and is high in reliability, security and efficiency.

Description

Technical Field

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

[0002] With the continued development of the information technology revolution and the arrival of the big data era, data is undoubtedly the most important asset for enterprises and individuals, thus greatly increasing the security risks caused by data breaches. Furthermore, the forgery and tampering of various messages are rampant. To reduce or avoid these situations during communication, various secure communication technologies have become a research hotspot in the field of confidential communication.

[0003] Secure communication technologies aim to ensure that confidential information is not only interpretable to the two authorized communicating parties, but also that it should not be tampered with during transmission. Currently, quantum communication technology is considered one of the most important secure communication technologies.

[0004] Existing quantum key distribution protocols, such as BB84, E91, and BBM92, primarily aim to generate a random key sequence between two parties (the sender Alice and the receiver Bob), using this random key sequence along with a quantum one-time pad to achieve encrypted data communication. However, these quantum key distribution methods have relatively high communication complexity; moreover, in actual transmission, especially during key distribution, key storage, and ciphertext transmission, the risk of data leakage still exists. Summary of the Invention

[0005] The purpose of this invention is to provide a quantum-secure direct communication method based on quantum walks that is highly reliable, secure, and efficient.

[0006] The quantum-secure direct communication method based on quantum walk provided by this invention includes the following steps:

[0007] Quantum channel preparation phase:

[0008] S1. Encode the initial state of the quantum walk system;

[0009] S2. Perform a quantum walk based on the directed loop graph on the quantum state obtained in step S1 to obtain a shared entangled state that can be used as a quantum channel;

[0010] Channel detection phase:

[0011] S3. The quantum channel shared by the sender and receiver is redescribed as a position-based measurement basis and a coin-based measurement basis;

[0012] S4. The sender uses a location-based measurement basis for measurement and sends the entangled state used for measurement to the receiver;

[0013] S5. After obtaining the entangled state sent by the sender, the receiver performs the corresponding measurement using a coin-based measurement basis;

[0014] S6. The sender and receiver compare their respective measurement results with all possible output results to detect and determine the quantum channel:

[0015] If the quantum channel is determined to be secure, proceed to the next steps;

[0016] Otherwise, communication ends;

[0017] Secret information transmission phase:

[0018] S7. Calculate the composite quantum state of the communication system;

[0019] S8. Perform a second step based on quantum walk on the directed loop graph on the quantum state obtained in step S7 to obtain the final quantum entangled state of the sender and receiver;

[0020] S9. The sender performs a projection measurement on the quantum state obtained in step S8 and transmits the data to the receiver;

[0021] S10. The receiver performs measurements based on the received data to obtain secret information and completes quantum-secure direct communication based on quantum walk.

[0022] Encoding the initial state of the quantum walk system as described in step S1 specifically includes the following steps:

[0023] Consider a quantum walk model based on a directed loop graph, which includes a location space and a coin space named coin 1; the sender holds the sender's first particle A1, and the receiver holds the receiver's first particle B1;

[0024] The position state in the position space is encoded and transmitted to the first particle A1 of the sender; the coin 1 state in the coin 1 space is encoded and transmitted to the first particle B1 of the receiver.

[0025] The sender prepares an initial state |0> on its first particle A1, and the receiver prepares an initial state |0> on its first particle B1; therefore, the initial state of the quantum walk system is expressed as:

[0026]

[0027] in For tensor product operation; |ψ>0 is the initial state of the quantum walk system.

[0028] Step S2, which involves performing a one-step quantum walk on the directed loop graph based on the quantum state obtained in step S1 to obtain a shared entangled state for use as a quantum channel, specifically includes the following steps:

[0029] Performing a quantum walk based on the directed loop graph at the quantum state |ψ>0, the sender and receiver obtain an entangled state that can be used as a quantum channel;

[0030] The quantum walk is described by the following formula:

[0031]

[0032] In the formula U 1 T is the coin operator acting on the first particle B1 of the receiver (coin state 1); circle For conditional shift operators acting on the entire system; I p The unit operator is the one that acts on the first particle A1 (position state) of the sender. For any single-qubit operation, such as the unit gate I, the Hadamard gate H, etc.; when At that time, the quantum state |ψ>1 after one quantum walk evolution is obtained as Where H is a Hadamard gate.

[0033] Steps S1 and S2 can be repeated several times to prepare a set number of quantum states, thereby preparing for subsequent channel detection and secret message transmission. Meanwhile, the entanglement preparation process in the quantum channel preparation stage adopts the method of first distributing and then automatically generating the required shared entangled states after one quantum walk.

[0034] Step S3, which describes re-describing the quantum channel shared by the sender and receiver as a position-based measurement basis and a coin-based measurement basis, specifically includes the following steps:

[0035] The quantum channel |ψ>1 shared by the sender and receiver is redescribed as a position-based measurement basis {|0>,|1>,|2>,|3>} and a coin-based measurement basis {|+>,|->}, denoted as...

[0036]

[0037] in

[0038] Step S4 involves the sender performing measurements using a location-based measurement basis and transmitting the entangled states used for measurement to the receiver. Specifically, this includes the following steps:

[0039] Set a subset of entangled states {|ψ>1} with a number of elements less than a set value; the sender first measures the first particle A1 using the measurement basis {|0>,|1>,|2>,|3>}, and then the sender sends the selected entangled state to the receiver.

[0040] After obtaining the entangled state sent by the sender, the receiver in step S5 performs the corresponding measurement using a coin-based measurement basis, specifically including the following steps:

[0041] After receiving the entangled state sent by the sender for measurement, the receiver uses the measurement basis {|+>,|->} to measure the receiver's first particle B1 corresponding to the entangled state.

[0042] Step S6 involves the sender and receiver comparing their respective measurement results with all possible output results to detect and determine the quantum channel. This process specifically includes the following steps:

[0043] The sender and receiver compare their respective measurement results with the possible outputs; after comparing all outputs:

[0044] If the error rate is less than the set confidence threshold, the sender and receiver determine that the quantum channel is secure and proceed with the next steps.

[0045] Otherwise, the sender and receiver will determine that the quantum channel is insecure, and the communication will end.

[0046] Step S7 involves calculating the composite quantum state of the communication system, specifically including the following steps:

[0047] By combining the sender's first particle A1, the sender's second particle A2, and the receiver's first particle B1, the composite quantum state of the communication system is obtained as follows: for:

[0048]

[0049] In the formula, |φ> represents the quantum state of the second particle A2 sent by the sender. m is the coefficient of the quantum ground state |1>, taking values ​​of 1 and -1.

[0050] Step S8 describes the second step of performing a quantum walk on a directed loop graph based on the quantum state obtained in step S7 to obtain the final quantum entangled state of the sender and receiver. Specifically, this includes the following steps:

[0051] Perform the second step based on quantum walks on directed cycle graphs In quantum state The coin state 2 located on the second particle A2 of the sender is the control state, and the position state located on the first particle A1 of the sender is the target state. The final quantum entangled state obtained by the sender and receiver is:

[0052]

[0053] U 2 The second step is based on the quantum walk operator on directed ring graphs; I p I1 is the unit operator acting on the first particle A1 (position state) of the sender; I1 is the unit operator acting on the first particle B1 (coin 1 state) of the receiver; T c ′ ircle For a conditional shift operator acting on a three-particle quantum walk system, and Where mod represents the modulo operation.

[0054] Step S9, which involves the sender performing a projection measurement on the quantum state obtained in step S8 and transmitting the data to the receiver, specifically includes the following steps:

[0055] The sender in the quantum state Projection measurements are performed on the second sender particle A2 and the first sender particle A1: The sender first uses the measurement basis {|+>,|->} to measure the second sender particle A2 and records the corresponding measurement output as {1,-1}; then the sender uses the measurement basis {|0>,|1>,|2>,|3>} to measure the first sender particle A1 and records the corresponding measurement output as {0,1,2,3}; finally, the sender transmits the measurement outputs on the second sender particle A2 and the first sender particle A1 to the receiver.

[0056] Step S10, where the receiver performs measurements to obtain secret information based on the received data, specifically includes the following steps:

[0057] Based on the measurement outputs received from the sender on the sender's second particle A2 and first particle A1, the receiver directly measures the receiver's first particle B1 using the measurement basis {|+>,|->} to obtain the secret information; alternatively, the receiver first performs a set local unitary operation on the receiver's first particle B1, and then uses the measurement basis {|+>,|->} to obtain the secret information; through the relationship between the above two methods and the measurement basis used, the receiver obtains the final measurement output result.

[0058] The quantum-secure direct communication method based on quantum walks provided by this invention utilizes a first step—a quantum walk on a directed loop graph—to deterministically prepare the necessary entangled state between the sender and receiver as a quantum channel. Compared to existing entanglement-based quantum-secure direct communication methods, this method avoids the pre-preparation of entangled states, instead generating them automatically after the first quantum walk, thus mitigating security risks in particle distribution. Simultaneously, this invention utilizes a second step—a quantum walk on a directed loop graph—along with a corresponding quantum teleportation method to transmit secret information. The applied quantum walk-based quantum teleportation method uses two local projection measurements instead of the existing Bell joint measurement, resulting in higher measurement efficiency and easier experimental implementation. Therefore, this invention features high reliability, high security, high efficiency, and ease of implementation. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0060] like Figure 1 The diagram shown is a schematic representation of the method flow of the present invention: The quantum-safe direct communication method based on quantum walk provided by the present invention includes the following steps:

[0061] Quantum Channel Preparation Phase: This phase aims to prepare entangled states as a quantum channel to meet the communication needs between sender Alice and receiver Bob.

[0062] S1. Encode the initial state of the quantum walk system; specifically, this includes the following steps:

[0063] Consider a quantum walk model based on a directed loop graph, which includes a location space and a coin space named coin 1; the sender holds the sender's first particle A1, and the receiver holds the receiver's first particle B1;

[0064] The position state in the position space is encoded and transmitted to the first particle A1 of the sender; the coin 1 state in the coin 1 space is encoded and transmitted to the first particle B1 of the receiver.

[0065] The sender prepares an initial state |0> on its first particle A1, and the receiver prepares an initial state |0> on its first particle B1; therefore, the initial state of the quantum walk system is expressed as:

[0066]

[0067] in This represents the tensor product operation; |ψ>0 represents the initial state of the quantum walk system;

[0068] S2. Perform a quantum walk based on the directed loop graph on the quantum state obtained in step S1 to obtain a shared entangled state that can be used as a quantum channel; specifically including the following steps:

[0069] Performing a quantum walk based on the directed loop graph at the quantum state |ψ>0, the sender and receiver obtain an entangled state that can be used as a quantum channel;

[0070] The quantum walk is described by the following formula:

[0071]

[0072] In the formula U 1 T is the coin operator acting on the first particle B1 of the receiver (coin state 1); circle For conditional shift operators acting on the entire system; I p The unit operator acting on the first particle A1 (position state) of the sender; For any single-qubit operation, such as the unit gate I, the Hadema gate H, etc.; when At that time, the quantum state |ψ>1 after one quantum walk evolution is obtained as Where H stands for Hademamen;

[0073] In practice, steps S1 and S2 can be repeated several times to prepare a set number of quantum states, thus preparing for subsequent channel detection and secret message transmission. Meanwhile, the entanglement preparation process in the quantum channel preparation stage adopts the method of first distributing and then automatically generating the required shared entangled states after one quantum walk, which is different from the existing method of preparing first and then distributing.

[0074] Channel detection phase: This phase aims to detect the security of the channel |ψ>1;

[0075] S3. Redefine the quantum channel shared by the sender and receiver as a position-based measurement basis and a coin-based measurement basis; specifically including the following steps:

[0076] The quantum channel |ψ>1 shared by the sender and receiver is redescribed as a position-based measurement basis {|0>,|1>,|2>,|3>} and a coin-based measurement basis {|+>,|->}, denoted as...

[0077]

[0078] in

[0079] S4. The sender performs measurements using a location-based measurement basis and transmits the entangled states used for the measurements to the receiver; specifically, this includes the following steps:

[0080] Set a subset of entangled states {|ψ>1} with a number of elements less than a set value; the sender first measures the first particle A1 using the measurement basis {|0>,|1>,|2>,|3>}, and then the sender sends the selected entangled state to the receiver;

[0081] S5. After obtaining the entangled state sent by the sender, the receiver performs the corresponding measurement using a coin-based measurement basis; specifically, it includes the following steps:

[0082] After receiving the entangled state sent by the sender for measurement, the receiver uses the measurement basis {|+>,|->} to measure the receiver's first particle B1 corresponding to the entangled state;

[0083] S6. The sender and receiver compare their respective measurement results with all possible output results to detect and determine the quantum channel:

[0084] If the quantum channel is determined to be secure, proceed to the next steps;

[0085] Otherwise, communication ends;

[0086] The specific implementation includes the following steps:

[0087] The sender and receiver compare their respective measurement results with the possible outputs; after comparing all outputs:

[0088] If the error rate is less than the set confidence threshold (generally set at 2% to 8.9%), the sender and receiver determine that the quantum channel is secure and proceed with the next steps.

[0089] Otherwise, eavesdropping may have already occurred, and the sender and receiver may have determined that the quantum channel is insecure, thus ending the communication.

[0090] Table 1 shows the measurement outputs of Alice and Bob and the corresponding quantum states:

[0091] Table 1 Measurement results and quantum state diagrams

[0092] Measurement results on A2 Measurement results on B1 correlated quantum states 1 1 |1>|+> 1 -1 |1>|-> 3 1 |3>|+> 3 -1 |3>|->

[0093] Secret Message Transmission Phase: This phase aims to facilitate the communication of secret information between Alice and Bob;

[0094] Alice possesses a second sender particle, A2, which carries another coin-2 state. The quantum walk model now consists of one location space and two coin spaces. Suppose Alice wants to transmit the classical secret message string 10101010 to Bob; Alice encodes it in a coin-2 state. Where m = 1 and -1; for example, classical bit 1 is encoded in the quantum state of coin 2. Above, classical bit 0 is encoded in the quantum state of coin 2. Therefore, the original classical secret information string is transformed into a quantum state sequence (|+>,|->,|+>,|->,|+>,|->,|+>,|->); Alice prepares the initial state of particle A2 as |φ>, which can be achieved by executing the Hadmamen H on the reference state |0> or |1>. Following this method, the task of transmitting classical secret information is transformed into the task of transmitting quantum states. For such tasks, quantum teleportation in quantum communication provides a better way to accomplish them, by fully utilizing quantum entanglement as a quantum channel. In particular, quantum teleportation based on quantum walks does not require the prior preparation of the necessary entangled states, but is automatically generated after one quantum walk. Furthermore, traditional quantum joint measurement can be replaced by quantum projection measurement, resulting in higher measurement efficiency and easier experimental implementation. Therefore, Alice achieves the communication of classical secret information by executing quantum teleportation based on quantum walks to orderly complete the communication task of the quantum state sequence.

[0095] S7. Calculate the composite quantum state of the communication system; specifically, this includes the following steps:

[0096] By combining the sender's first particle A1, the sender's second particle A2, and the receiver's first particle B1, the composite quantum state of the communication system is obtained as follows: for:

[0097]

[0098] In the formula, |φ> represents the quantum state of the second particle A2 sent by the sender. m is the coefficient of the quantum ground state |1>, which takes values ​​of 1 and -1;

[0099] S8. Perform a second step based on a directed loop graph quantum walk on the quantum state obtained in step S1 to obtain the final quantum entangled state of the sender and receiver; specifically including the following steps:

[0100] Perform the second step based on quantum walks on directed cycle graphs In quantum state The coin state 2 located on the second particle A2 of the sender is the control state, and the position state located on the first particle A1 of the sender is the target state. The final quantum entangled state obtained by the sender and receiver is:

[0101]

[0102] U 2The second step is based on the quantum walk operator on directed ring graphs; I p I1 is the unit operator acting on the first particle A1 (position state) of the sender; I1 is the unit operator acting on the first particle B1 (coin 1 state) of the receiver; T c ′ ircle For a conditional shift operator acting on a three-particle quantum walk system, and Where mod represents the modulo operation;

[0103] S9. The sender performs a projection measurement on the quantum state obtained in step S8 and transmits the data to the receiver; specifically, this includes the following steps:

[0104] The sender in the quantum state Projection measurements are performed on the second sender particle A2 and the first sender particle A1: The sender first uses the measurement basis {|+>,|->} to measure the second sender particle A2 and records the corresponding measurement output as {1,-1}; then the sender uses the measurement basis {|0>,|1>,|2>,|3>} to measure the first sender particle A1 and records the corresponding measurement output as {0,1,2,3}; finally, the sender transmits the measurement outputs on the second sender particle A2 and the first sender particle A1 to the receiver.

[0105] S10. The receiver, based on the received data, performs direct measurement or first executes an appropriate local unitary operation before measurement to obtain the secret information, thus completing quantum-secure direct communication based on quantum walks; specifically including the following steps:

[0106] Based on the measurement outputs received from the sender on the sender's second particle A2 and first particle A1, the receiver directly measures the receiver's first particle B1 using the measurement basis {|+>,|->} to obtain the secret information; alternatively, the receiver first performs a set local unitary operation on the receiver's first particle B1, and then uses the measurement basis {|+>,|->} to obtain the secret information; through the relationship between these two methods and the measurement basis used, the receiver obtains the final measurement output result.

[0107] In practice, based on Alice's measurement outputs on particles A2 and A1, Bob directly measures particle B1 using the measurement basis {|+>,|->} to obtain the secret information. On the other hand, Bob first performs a suitable local unitary operation on particle B1, such as... Then, the measurement basis {|+>,|->} is used to obtain the secret information, where Z and X are respectively... and

[0108] Therefore, by using the two methods described above and the relationship between the measurement bases used (<+|->=0), Bob can always interpret his measurement output. For example, if he wants to communicate quantum states... (Corresponding to classic secret information 1), if Alice's measurement results are 1 and 2, then Bob directly uses the measurement basis {|+>,|->} to measure particle B1 to obtain the original secret information 1. To transmit secret information 1, the relationship between Alice's measurement results on particles A2 and A1 and Bob's local unitary operation on particle B1 is shown in Table 2.

[0109] Table 2 Measurement Results and Local Unitary Operation Diagram

[0110] Measurement results on A2 Measurement results on A1 Local unitary operation on B1 1 -1 I -1 2 Z 1 0 X -1 0 XZ

[0111] Similarly, if we want to communicate quantum states... (Corresponding to classic secret information 0), if Alice's measurement output is -1 and 2, Bob first performs a Z operation on particle B1, and then uses the measurement basis {|+>,|->} to measure particle B1 to obtain the original secret information 0. To transmit secret information 0, Alice's measurement outputs on particles A2 and A1 and Bob's local unitary operation on particle B1 are listed in Table 3.

[0112] Table 3 Measurement Results and Local Unitary Operation Diagram Table 2

[0113] Measurement results on A2 Measurement results on A1 Local unitary operation on B1 1 2 Z -1 2 I 1 0 XZ -1 0 X

[0114] Therefore, in summary, the method of the present invention has the characteristics of high reliability, good safety and high efficiency.

Claims

1. A quantum-safe direct communication method based on quantum walks, comprising the following steps: Quantum channel preparation phase: S1. Encode the initial state of the quantum walk system; S2. Perform a one-step quantum walk based on the directed loop graph on the quantum state obtained in step S1 to obtain a shared entangled state that can be used as a quantum channel; specifically including the following steps: Performing a quantum walk based on a directed cycle graph in a quantum state The sender and receiver obtain entangled states that serve as a quantum channel; The quantum walk is described by the following formula: In the formula For the coin operator acting on the first particle B1 of the receiver; A conditional shift operator that operates on the entire system; The unit operator acting on the first particle A1 of the sender; For any single-qubit operation; when At that time, the quantum state after the one-step quantum walk evolution is obtained. for ,in For Hademamen; This represents the initial state of the quantum walk system. Channel detection phase: S3. The quantum channel shared by the sender and receiver is redescribed as a position-based measurement basis and a coin-based measurement basis; S4. The sender performs measurements using a location-based measurement basis and sends the entangled states used for the measurements to the receiver; S5. After obtaining the entangled state sent by the sender, the receiver performs the corresponding measurement using a coin-based measurement basis; S6. The sender and receiver compare their respective measurement results with all possible output results to detect and determine the quantum channel: If the quantum channel is determined to be secure, proceed to the next steps; Otherwise, communication ends; Secret information transmission phase: S7. Calculate the composite quantum state of the communication system; specifically including the following steps: By combining the sender's first particle, the sender's second particle, and the receiver's first particle, the composite quantum state of the communication system is obtained as follows: for: In the formula Let A2 be the quantum state of the second particle sent by the sender, where ; quantum ground state The coefficient takes values ​​of 1 and -1; S8. Perform a second step based on a directed loop graph quantum walk on the quantum state obtained in step S1 to obtain the final quantum entangled state of the sender and receiver; specifically including the following steps: Perform the second step based on quantum walks on directed cycle graphs In quantum state The coin state 2, located on the second particle of the sender, is the control state, and the position state, located on the first particle of the sender, is the target state. The final quantum entangled state obtained by the sender and receiver is: in The second step is based on the quantum walk operator on the directed ring graph; The unit operator acting on the first receiving particle B1; For a conditional shift operator acting on a three-particle quantum walk system, and Where mod is the modulo operation; S9. The sender performs a projection measurement on the quantum state obtained in step S8 and transmits the data to the receiver; S10. The receiver performs measurements based on the received data to obtain secret information and completes quantum-secure direct communication based on quantum walk.

2. The quantum-secure direct communication method based on quantum walks according to claim 1, characterized in that... Encoding the initial state of the quantum walk system as described in step S1 specifically includes the following steps: Consider a quantum walk model based on a directed cycle graph, which includes a location space and a coin space named coin 1; the sender holds the sender's first particle, and the receiver holds the receiver's first particle; The encoding is located in the position space and is applied to the first particle of the sender; the encoding is located in the coin 1 space and is applied to the first particle of the receiver. The sender prepares the initial state located on the sender's first particle as follows: The receiver prepares the initial state located on the receiver's first particle as follows: Therefore, the initial state of the quantum walk system is expressed as: in For tensor product operations; This represents the initial state of the quantum walk system.

3. The quantum-secure direct communication method based on quantum walk according to claim 2, characterized in that... Steps S1 and S2 can be repeated several times to prepare a set number of quantum states, thereby preparing for subsequent channel detection and secret message transmission. Meanwhile, the entanglement preparation process in the quantum channel preparation stage adopts the method of first distributing and then automatically generating the required shared entangled states after one quantum walk.

4. The quantum-secure direct communication method based on quantum walk according to claim 3, characterized in that... Step S3, which describes re-describing the quantum channel shared by the sender and receiver as a position-based measurement basis and a coin-based measurement basis, specifically includes the following steps: Quantum channel shared by sender and receiver Redescribed as a location-based measurement basis and coin-based measurement base , represented as in , .

5. The quantum-secure direct communication method based on quantum walk according to claim 4, characterized in that... Step S4 involves the sender performing measurements using a location-based measurement basis and transmitting the entangled states used for measurement to the receiver. Specifically, this includes the following steps: Given a set of entangled states A subset whose number of elements is less than a set value; the sender first uses a measurement base The sender measures the first particle, and then the sender sends the selected entangled state to the receiver.

6. The quantum-secure direct communication method based on quantum walk according to claim 5, characterized in that... After obtaining the entangled state sent by the sender, the receiver in step S5 performs the corresponding measurement using a coin-based measurement basis, specifically including the following steps: After receiving the entangled state sent by the sender for measurement, the receiver uses the measurement basis. Measure the first particle of the receiver corresponding to the entangled state.

7. The quantum-secure direct communication method based on quantum walk according to claim 6, characterized in that... Step S6 involves the sender and receiver comparing their respective measurement results with all possible output results to detect and determine the quantum channel. This process specifically includes the following steps: The sender and receiver compare their respective measurement results with the possible outputs; after comparing all outputs: If the error rate is less than the set confidence threshold, the sender and receiver determine that the quantum channel is secure and proceed with the next steps. Otherwise, the sender and receiver will determine that the quantum channel is insecure, and the communication will end.

8. The quantum-secure direct communication method based on quantum walk according to claim 7, characterized in that... Step S9, which involves the sender performing a projection measurement on the quantum state obtained in step S8 and transmitting the data to the receiver, specifically includes the following steps: The sender in the quantum state Projection measurements are performed on the second and first particles of the sender: the sender first uses a measurement base... Measure the second particle sent by the sender and record the corresponding measurement output results. Then the sender uses a measurement base. Measure the first particle from the sender and record the corresponding measurement output. Finally, the sender transmits the measurement outputs from the sender's second particle and the sender's first particle to the receiver. Step S10, where the receiver performs measurements to obtain secret information based on the received data, specifically includes the following steps: Based on the measurement outputs received from the sender at the sender's second and first particles, the receiver uses a measurement basis. The secret information can be obtained by directly measuring the first particle of the receiver; alternatively, the receiver can first perform a predefined local unitary operation on the first particle of the receiving method, and then use a measurement base. To obtain secret information; through the relationship between the above two methods and the measurement basis used, the receiver obtains the final measurement output result.

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