Receiving device independent quantum secure direct communication method

Abstract

The invention discloses a receiving equipment independent quantum secure direct communication method. A user Alice randomly selects a preparation base to prepare a large number of single photons, the photons are randomly divided into sequences S1, S2 and S3, and the sequences S1, S2 and S3 serve as a first-round safety detection photon sequence, a second-round safety detection photon sequence and an information transmission photon sequence respectively. And the Alice performs random operation on the photons in the sequence S3, and sends all the photons to the user Bob in sequence. After photon transmission is completed, Bob carries out first-round receiving equipment irrelevant safety detection, codes a photon sequence S3 in a hand after confirming safety, disorganizes the photon sequence and sends the disorganized photon sequence back to Alice; and the Alice performs a second round of receiving equipment irrelevant safety detection. And after the safety is confirmed, the Alice recovers the original information photon sequence for decoding. According to the invention, all attacks aiming at receiving equipment can be resisted, and the security of quantum secure direct communication is improved. According to the method, complex Bell state measurement is not needed, only single photon measurement is needed, experimental operation can be effectively simplified, and high practicability is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum communication, and in particular relates to a receiving device-independent quantum secure direct communication method. Background Art

[0002] Quantum secure communication is an important branch of quantum communication, with the main purpose of protecting information security. Quantum secure communication has the ability to sense eavesdropping, which is called absolute security, which is its biggest advantage over classical communication. The security of quantum communication is guaranteed by some basic principles in quantum mechanics, such as the uncertainty principle, the quantum non-cloning principle, and the measurement collapse principle. There are now many types of quantum secure communication protocols, mainly including quantum key distribution (QKD), quantum direct secure communication (QSDC), quantum secret sharing (QSS), etc. QKD and QSS are to establish a random key between the two or more communicating parties, while QSDC uses quantum channels to directly transmit information, and the communicating parties do not need to share keys in advance. In 2000, Long Guilu and Liu Xiaoshu proposed the first efficient QSDC protocol based on EPR entangled photon pairs. In 2003, Long Guilu, Deng Fuguo, Liu Xiaoshu and others proposed a two-step QSDC protocol using quantum dense coding. In 2004, Deng Fuguo and Long Guilu proposed the single-photon-based DL04 method, which integrates the non-cloning property of unknown quantum states into the "one-time-one-pad" encryption system, gives the conditions that QSDC needs to meet and explains its physical mechanism.

[0003] However, under actual conditions, the physical devices used by the communicating parties may have security risks, so it is necessary to ensure the security of the devices when transmitting information. In order to prevent attacks on physical devices, device-independent communication protocols and measurement device-independent communication protocols have been proposed. Device-independent communication protocols require high-quality entangled pairs and high detection efficiency, and measurement device-independent communication protocols require the participation of a third party.

[0004] Quantum direct secure communication (QSDC) can directly transmit information through quantum channels, but the imperfections of actual physical devices may lead to security risks during the communication process. Existing device-independent protocols require high-quality entangled pairs and extremely high detection efficiency, which are difficult to meet under current experimental conditions. Summary of the invention

[0005] The purpose of the present invention is to address the defects and shortcomings of the above-mentioned prior art and propose a receiving device-independent quantum secure direct communication method. This method uses an efficient single-photon source under current experimental conditions to prepare single photons under different bases, and confirms the security of communication based on the probability distribution of the measurement results of a large number of security detection photons. It can resist all attacks on the receiving device and enhance the security of quantum direct secure communication (QSDC) under actual experimental conditions. Moreover, the present invention does not require the complex Bell state analysis required by the traditional QSDC method, but only requires simple single-photon measurement, which can effectively simplify the experimental operation and improve communication efficiency. Therefore, the present invention has the advantages of high security and high practicality, and has important applications in the field of quantum secure communication in the future.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a receiving device-independent quantum secure direct communication method, which proposes receiving device-independent quantum secure direct communication based on single photons, including the following steps:

[0007] Step 1: The information receiver Alice and the information sender Bob each have a sequence {X}={x1,x2,…x n} and the sequence {Y}={y1,y2,……y n}. Every positive integer x in the sequence i and i (i=1,2,…n) can generate a preparation basis. Therefore, Alice and Bob each have n different bases.

[0008] Step 2: Alice randomly selects integers x from the sequence {X} i Generate a preparation base and prepare 3r single photons (r is a large number). Then randomly select r photons to form photon sequence S1, r photons to form photon sequence S2, and r photons to form photon sequence S3. The photons in sequence S1 are the first security detection photons, the photons in sequence S2 are the second security detection photons, and the photons in sequence S3 are information transmission photons. Alice performs random operations on the photons in sequence S3.

[0009] Step 3: Alice sends all photons to the communication party Bob in sequence.

[0010] Step 4: After receiving all the photons, Bob first stores them in the quantum memory. Then Alice announces the position of the photons in sequence S1. Bob extracts the photons of sequence S1 from the quantum memory and records the missing photons. For each photon, he randomly selects y in the sequence {Y}. iGenerate a measurement basis and measure it to perform the first round of security testing. Bob then publishes the measurement basis and measurement results of each photon. Alice then calculates the theoretical probability distribution of the measurement results based on the preparation basis and measurement basis of each photon, and compares it with the probability distribution of the actual measurement results published by Bob. If the probability distribution of Bob's measurement value deviates too much from the theoretical calculated value, it is considered that the photon transmission process is unsafe or the receiving device is unsafe, and the communication is canceled. If the deviation of the probability distribution of Bob's measurement value from the calculated value is within the allowable range, it is considered that there is no eavesdropping during the first round of photon transmission in the channel, and Bob's receiving device is safe, then proceed to the next step.

[0011] Step 5: Alice announces the position of the photons in sequence S3, and then Bob extracts the photons in sequence S3 from the quantum memory and encodes the information to be transmitted into the corresponding photons in sequence. Subsequently, Bob extracts the photons in sequence S2 from the quantum memory, scrambles the positions of the photons in sequences S2 and S3, and then sends all the photons back to Alice in sequence through the quantum channel.

[0012] Step 6: After Alice receives all the photons, she first stores them in the quantum memory. Then Bob announces the position of the photons in sequence S2. Alice extracts the photons of sequence S2 from the quantum memory and records the lost photons. She generates a measurement basis based on the preparation basis of the photons of sequence S2 and measures them for the second round of security detection. Bob then announces the original order of the photons of sequence S2. Alice calculates the theoretical probability distribution of the measurement results based on the preparation basis and measurement basis of each photon. If the probability distribution of Alice's measurement value deviates too much from the theoretical calculated value, the photon transmission process is considered unsafe and the communication is canceled. If the deviation between the probability distribution of Bob's measurement value and the calculated value is within the allowable range, it means that the security test has passed and the next step is performed.

[0013] Step 7: Bob publishes the original order of photons in sequence S3. Alice extracts all coded photons and restores the original information transmission photon sequence. She measures each photon using its original preparation basis and compares it with its initial state to decipher the information transmitted by the communication party Bob.

[0014] Furthermore, in the above step 1 of the present invention, x i The generated preparation base is By i The generated preparation base is Among them, θ is |0> and |1> represent the horizontal and vertical polarization of the photon, respectively.

[0015] Furthermore, in the above step 2 of the present invention, the information receiver Alice randomly selects an integer x from the sequence {X}i The generation preparation base prepares 3r photons, and the quantum state of each photon is:

[0016] The preparation sequences of the photons of sequences S1, S2, and S3 are {X1}, {X2}, and {X3}, respectively, which can be described as:

[0017] {X1}={a1,a2,a3,……,a r}

[0018] {X2}={b1,b2,b3,……,b r}

[0019] {X3}={c1,c2,c3,......,c r}

[0020] where a r 、b r 、c r is an integer xi randomly selected from the sequence {X}.

[0021] Alice performs random operations on the sequence S3 photons, which can be described as:

[0022]

[0023] Among them, U0 and U1 represent the identity operation and phase flip operation respectively. After the U0 and U1 operations, the quantum state evolution of the photon is:

[0024]

[0025]

[0026] Furthermore, the safety detection process in the above step 4 of the present invention is:

[0027] After receiving all the photons, the communicating party Bob first stores the photons in the quantum memory. Then Alice announces the position of the photons in sequence S1. Bob extracts the photons of sequence S1 from the quantum memory and records the missing photons. In the sequence {Y} = {y1, y2, y3, ..., y n} randomly select y i Generate measurement basis |ψ y >, perform binary measurement after M operation, M operation can be described as:

[0028] Here, y i represents the i-th element in the sequence {Y}, where y represents the result of the binary measurement. When y = 0, it means that after the M operation |ψx > is projected onto If y=1, it means that after the M operation |ψ x >Not projected to

[0029] When Bob performs the first round of security testing, the randomly selected preparation base composition sequence {Y1} can be described as:

[0030] {Y1}={w1,w2,w3,......,w r}

[0031] where w r is an integer yi randomly selected from the sequence {Y}.

[0032] Bob publishes the measurement basis and measurement results of each photon. Alice calculates the theoretical probability distribution of the measurement results based on the preparation basis and measurement basis of each photon, which can be described as:

[0033]

[0034]

[0035] If the probability distribution of Bob's measurement value deviates too much from the theoretical calculation, the photon transmission process is considered to be unsafe or the receiving device is unsafe, and the communication is canceled. If the probability distribution of Bob's measurement value deviates within the allowable range, it can be considered that there is no eavesdropping during the first round of photon transmission in the channel and Bob's receiving device is safe, and the next step is carried out.

[0036] Furthermore, the two operators used for encoding in the above step 5 of the present invention are:

[0037]

[0038] Among them, U0 and U1 represent the classical information 0 and 1 respectively.

[0039] The preparation sequences {X2} and {X4} of the disrupted sequence S2 photons can be described as:

[0040] {X2}={b1,b2,b3,......,b r}

[0041] {X4}={d1,d2,d3,……,d r}

[0042] Among them, b r and d r Represents the preparation sequence element of the r-th photon before and after scrambling.

[0043] Furthermore, the safety detection process in step 6 of the present invention is as follows:

[0044] After Alice receives all the photons, she first stores them in the quantum memory. Then Bob announces the positions of the photons in the scrambled sequence S2. Alice extracts the photons of the scrambled sequence S2 from the quantum memory, records the missing photons, and measures them based on the measurement basis generated by the sequence {X2}, which can be described as:

[0045] Where b represents the measurement result, b i It represents the i-th element in the sequence {X2}.

[0046] Bob announces the scrambled order of S2 photons, and Alice calculates the theoretical probability distribution of the measurement results based on the sequences {X2} and {X4}, which can be described as:

[0047]

[0048]

[0049] If the probability distribution of Alice's measurement value deviates too much from the theoretical calculation, the photon transmission process is considered unsafe and the communication is cancelled. If the probability distribution deviation of Bob's measurement value is within the allowable range, it means that there is no eavesdropping during the second round of photon transmission in the channel and Alice's receiving device is safe, so proceed to the next step.

[0050] Furthermore, in the above step 7 of the present invention, Bob publishes the scrambled order of information transmission photons, Alice extracts all coded photons, performs binary measurement on all coded photons according to the sequence {X3}, and performs random operations on the sequence S3 to interpret the information transmitted by the communication party Bob, which can be described as:

[0051]

[0052]

[0053] in, Indicates that the c in the sequence {X3} i The single photon produced represents the photon used to transmit the classical information 0, represents the photon used to transmit the classical information 1, p(a=0) and p(a=1) represent the probabilities of measuring 0 and 1 respectively.

[0054] Furthermore, the capacity of the channel of the present invention can be estimated as:

[0055] C s =I(B:A)-I(B:E)

[0056] Among them, I(B:A) represents the mutual information between Bob and Alice, and I(B:E) represents the mutual information between Bob and Eve.

[0057] I(B:A)=Q BAB [1-h(E BAB )]

[0058]

[0059] Among them, Q BAB E represents the total gain of Alice detecting the photon sent by Bob, that is, after two rounds of photon transmission, the probability of the detector response caused by the photon sent back by Bob at Alice. BAB represents the total error rate of Alice reading the information transmitted by Bob, and h(x) = -xlog2 x-(1-x)log2(1-x) represents the binary Shannon entropy. Q s BE is the gain of photons stolen by Eve in the first round of photon transmission when the number of photons is s.

[0060]

[0061]

[0062] Among them, let the coupling coefficient between photons and optical fibers be η c , when photons are transmitted in the channel, the transmission efficiency η t =10 -aL / 10 (L is the photon transmission distance, a = 0.2dB / kM) The storage efficiency of quantum memory is η m , the detection efficiency of the photon detector is η d Y0 is the probability of a dark count occurring in the detector, δθ and δx i is the error that occurs in the actual quantum channel, and μ is the average number of photons.

[0063] Furthermore, the present invention can ensure that when the receiving device is a black box, the information transmission is still absolutely safe, effectively enhancing the safety of QSDC under actual experimental conditions. Moreover, the present invention only uses single photons and single photon measurements, and the signal photon preparation efficiency and detection efficiency are both high, that is, more than 90%, so the present invention has the characteristics of high safety and high efficiency.

[0064] Beneficial effects:

[0065] 1. The quantum secure direct communication process of the present invention has potential safety hazards due to the imperfect physical equipment, and it is difficult to achieve high-quality entangled pairs. Therefore, we will use the measurement collapse principle to probabilistically distribute the results obtained under different preparation bases. In the security test, we will not rely on the results displayed by the device to judge, but judge the security by the probability distribution of the measurement results. Finally, the information is transmitted through unitary operations.

[0066] 2. The measuring device and unitary operation device of the present invention are both commonly used optical devices. Especially under the existing experimental conditions, a half-wave plate (HWP), a polarization beam splitter (PBS), a detector and a phase modulator with a specific angle are used to realize single-photon measurement and unitary operation. Therefore, the present invention has stronger practicality and experimental operability.

[0067] 3. The present invention only uses single photons and single photon measurements, and the signal photon preparation efficiency and detection efficiency are both high, so it has the characteristics of high safety and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is a communication flow diagram of the receiving device-independent quantum secure direct communication method of the present invention.

[0069] Figure 2 It is a schematic diagram of the receiving device-independent quantum secure direct communication method of the present invention.

[0070] a) Alice prepares single photons according to the sequence {X}; b) Alice randomly shuffles the sequence S1, S2, and S3 photons and sends them to Bob; c) Bob stores the received photons in the quantum memory; d) Bob performs the first round of security checks according to the sequence {Y}; e) Bob encodes information on the sequence S3 photons; f) Bob randomly shuffles the sequence S2 and S3 photons and sends them to Alice; g) Alice performs the second round of security checks according to the sequence {X2}; h) Alice decodes the information according to the sequence {X3}. DETAILED DESCRIPTION

[0071] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. This example is only used to explain the present invention and does not constitute a limitation on the protection scope of the present invention.

[0072] The present invention takes n=r=5, and the random operations performed by Alice on the sequence S3 photons are all identical operations as an example, and the process of the present invention is analyzed in conjunction with a specific example below:

[0073] The information receiver Alice selects the preparation base according to the sequence {X} to generate 15 photons, which form the photon sequences S1, S2, and S3. The preparation sequences {X1}{X2}{X3} are:

[0074] {X1}={1,2,3,4,5}; {X2}={3,1,5,4,2}; {X3}={1,3,2,5,4}

[0075] The information sender Bob selects the measurement basis for the first round of security detection based on the sequence {Y}. The measurement basis sequence can be described as:

[0076] {Y1}={3,2,5,1,4}

[0077] Alice prepares single photon states according to the sequence {X} (i=1,2,3,4,5), where the single photons prepared by the sequence {X1} form the sequence S1, the single photons prepared by the sequence {X2} form the sequence S2, and the single photons prepared by the sequence {X3} form the sequence S3. The photons of sequence S1 are used as the first round of security detection photons, the photons of sequence S2 are used as the second round of security detection photons, and the photons of sequence S3 are used as information transmission photons. The quantum states of the photons are:

[0078]

[0079]

[0080] Among them, |0> and |1> represent the horizontal polarization and vertical polarization of the photon, respectively.

[0081] Then, Alice shuffles all the photons and sends them to the communication party Bob. After receiving all the photons, the communication party Bob first stores the photons in the quantum memory. Then Alice announces the position of the photons in sequence S1. Bob extracts the photons of sequence S1 from the quantum memory and records the missing photons. According to the sequence {Y1}={3,2,5,1,4}, each photon of S1 is measured in binary, which can be described as:

[0082] The first photon of sequence S1 is measured:

[0083]

[0084]

[0085]

[0086]

[0087] Perform the following operation on the second photon of sequence S1:

[0088]

[0089]

[0090]

[0091]

[0092] Perform the following operation on the third photon of sequence S1:

[0093]

[0094]

[0095]

[0096]

[0097] Perform the following operation on the fourth photon of sequence S1:

[0098]

[0099]

[0100]

[0101]

[0102] Perform the following operation on the fifth photon of sequence S1:

[0103]

[0104]

[0105]

[0106]

[0107] Then Bob announces the sequence {Y} = {3, 2, 5, 1, 4} and the measurement result {1, 0, 1, 1, 0}, that is, P(y = 0) = 0.4, P(y = 1) = 0.6 (P represents probability). At this time, Alice calculates the theoretical probability distribution based on {X1} and {Y}, which can be described as:

[0108]

[0109]

[0110] At this time, the actual probability distribution of the measurement result differs from the theoretical calculation by 0.0118. Since the number of photons r taken in the example is small, it is impossible to achieve the same size of the actual probability distribution and the theoretical calculation in a statistical sense. When the number of photons r is a large number, under the conditions of no eavesdropping and ideal channel, it can be strictly guaranteed that the actual probability distribution of the measurement result is the same as the theoretical calculation value. Under the actual noisy channel, the actual probability distribution of the measurement result has a slight deviation from the theoretical calculation value. In the actual communication process, if the probability distribution of Bob's measurement value deviates too much from the theoretical calculation, it is considered that there is eavesdropping in the photon transmission process, and the photon transmission process is unsafe, and the communication is canceled. If the probability distribution of Bob's measurement value deviates within the allowable range, it means that the security test has passed, and the next step is performed.

[0111] Alice announces the position of photon S3 in the sequence, and Bob extracts the corresponding photon from the quantum memory and encodes the photon using unitary operations U0 and U1. If Bob needs to transmit the classical information 10010, he performs U1U0U0U1U0 on the photons in the sequence S3 in his hand, which can be described as:

[0112]

[0113] Bob then extracts the photons of sequence S2 from the quantum memory, scrambles the photons of sequence S2 and S3, and sends them back to Alice, which can be described as:

[0114]

[0115]

[0116] Bob does not know the specific {X2} and {X4}, he only knows his own scrambled order. After Alice receives all the photons, she first stores them in the quantum memory. Then Bob announces the position of the photons in sequence S2. Alice extracts the photons of sequence S2 from the quantum memory and records the missing photons. She performs binary measurement based on sequence {X2} and conducts a second round of security testing. The specific process can be described as:

[0117] Perform the following operation on the first photon of sequence S2:

[0118]

[0119]

[0120]

[0121]

[0122] Perform the following operation on the second photon of sequence S2:

[0123]

[0124]

[0125]

[0126]

[0127] Perform the following operation on the third photon of sequence S2:

[0128]

[0129]

[0130]

[0131]

[0132] Perform the following operation on the fourth photon of sequence S2:

[0133]

[0134]

[0135]

[0136]

[0137] Perform the following operation on the fifth photon of sequence S2:

[0138]

[0139]

[0140]

[0141]

[0142] Then, Alice records the measurement results {0, 1, 0, 0, 1}, that is, P(b=0)=0.8, P(b=1)=0.2. Bob announces the scrambled order, and Alice learns the sequence {X4} and calculates the theoretical probability distribution, which can be described as:

[0143]

[0144]

[0145] Similar to the first round of security detection process, in the actual communication process, if the probability distribution of Alice's measurement value deviates too much from the theoretical calculation, the photon transmission process is considered unsafe and the communication is cancelled. If the probability distribution deviation of Alice's measurement value is within the allowable range, it means that the security test has passed and the next step is carried out.

[0146] Bob publishes the scrambled order of the photons in sequence S3. Then, Alice restores the photons in sequence S3 to their original order and performs binary measurement on the photons in sequence S3 according to the sequence {X3}, which can be described as:

[0147] Perform the following operation on the first photon of sequence S3:

[0148]

[0149]

[0150] Perform the following operation on the second photon of sequence S3:

[0151]

[0152]

[0153] Perform the following operation on the third photon of sequence S3:

[0154]

[0155]

[0156] Perform the following operation on the fourth photon of sequence S3:

[0157]

[0158]

[0159] Perform the following operation on the fifth photon of sequence S3:

[0160]

[0161]

[0162] Therefore, the actual measurement result is {1,0,0,1,0}, thus obtaining the secret information transmitted by Bob.

[0163] Figure 2 Schematic diagram of the single-photon receiving device-independent quantum secure direct communication method, HWP at The role of is to transform |0> into cosθ|0>+sinθ|1>, the role of PBS is to transmit |0> and reflect |1>, QM is quantum memory, PM is phase modulator, such as PM 1 is to add a phase to the i-th photon passing through the device The function of PM 4 is to add a phase e to the photons passing through the device. iπ , and PM 2 surrounded by a dotted line indicates that when an identity operation is performed, no light path is added, but when a phase flip is performed, the light path is added.

[0164] In summary, the present invention specifically includes Alice preparing a large number of single photons according to the sequence {X} to form sequences S1, S2, and S3 respectively, and sending them to the communication party. At this time, Alice announces the position of the first round of security detection photon S1, Bob performs binary measurement according to the sequence {Y}, and tells Alice the actual measurement result and sequence {Y1} through the classical authorization channel. Alice calculates the theoretical measurement result probability distribution according to the sequences {X1} and {Y1}, and compares to determine whether the first round of communication process and Bob's receiving device are safe. After the security test is passed, Alice announces the position of the information transmission photon S3, and Bob performs unitary operation on the sequence S3 photons in his hand according to the coding rules for the information he wants to transmit, and sends it back to Alice after randomly shuffling it. Subsequently, Bob announces the position of the second round of security detection photon S2, and Alice performs binary measurement according to the sequence {X2}, and records the distribution probability of the measurement results. Then Bob publishes the scrambled order of sequence S2 photons, and Alice calculates the theoretical probability distribution based on the sequences {X2} and {X4}, and compares them to determine whether the second round of communication process and Alice's receiving device are safe. After the security test is passed, Bob publishes the scrambled order of sequence S3 photons, and then Alice performs binary measurement based on the sequence {X3} to obtain the information transmitted by Bob. The present invention realizes quantum secure direct communication that is independent of the receiving device, and only requires simple single photon preparation and measurement, with high security and efficiency. This protocol plays an important role in promoting the practical application of quantum secure direct communication.

[0165] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A receiving device-independent quantum secure direct communication method, characterized in that: The steps include: Step 1: The information receiver Alice and the information sender Bob each have a sequence {X}={x1,x2,…x n } and the sequence {Y}={y1,y2,……y n }, every positive integer x in the sequence i and i (i=1,2,…n) can generate a preparation basis, Alice and Bob both have n different bases; Step 2: Alice randomly selects integers x from the sequence {X} i Generate a preparation base to prepare 3r single photons (r is a large number), then randomly select r photons to form photon sequence S1, r photons to form photon sequence S2, and r photons to form photon sequence S3. The photons in sequence S1 are the first security detection photons, the photons in sequence S2 are the second security detection photons, and the photons in sequence S3 are information transmission photons. Alice performs random operations on the photons in sequence S3. Step 3: Alice sends all photons to the communication party Bob in sequence; Step 4: After receiving all the photons, Bob first stores them in the quantum memory. Alice announces the position of the photons in sequence S1. Bob extracts the photons of sequence S1 from the quantum memory and records the lost photons. For each photon, he randomly selects y in the sequence {Y}. i Generate a measurement basis and measure it to conduct the first round of security detection. Bob publishes the measurement basis and measurement results of each photon. Alice calculates the theoretical probability distribution of the measurement results based on the preparation basis and measurement basis of each photon, and compares it with the probability distribution of the actual measurement results published by Bob. If the probability distribution of Bob's measurement value deviates too much from the theoretical calculated value, it is considered that the photon transmission process is unsafe or the receiving device is unsafe, and the communication is canceled. If the deviation between the probability distribution of Bob's measurement value and the calculated value is within the allowable range, it is considered that there is no eavesdropping during the first round of photon transmission in the channel, and Bob's receiving device is safe, then proceed to the next step. Step 5: Alice announces the position of the photons in sequence S3, Bob extracts the photons in sequence S3 from the quantum memory, encodes the information to be transmitted into the corresponding photons in sequence, Bob extracts the photons in sequence S2 from the quantum memory, scrambles the positions of the photons in sequences S2 and S3, and then sends all the photons back to Alice in sequence through the quantum channel; Step 6: After Alice receives all the photons, she first stores them in the quantum memory. Bob announces the position of the photons in sequence S2. Alice extracts the photons of sequence S2 from the quantum memory and records the lost photons. She generates a measurement basis based on the preparation basis of the photons of sequence S2 and measures them. A second round of security detection is performed. Bob announces the original order of the photons of sequence S2. Alice calculates the theoretical probability distribution of the measurement results based on the preparation basis and measurement basis of each photon. If the probability distribution of Alice's measurement value deviates too much from the theoretical calculated value, the photon transmission process is considered unsafe and the communication is canceled. If the deviation between the probability distribution of Bob's measurement value and the calculated value is within the allowable range, it means that the security detection has passed and the next step is performed. Step 7: Bob publishes the original order of photons in sequence S3. Alice extracts all coded photons and restores the original information transmission photon sequence. She measures each photon using its original preparation basis and compares it with its initial state to decipher the information transmitted by the communication party Bob.

2. A receiving device-independent quantum secure direct communication method according to claim 1, characterized in that: In step 1, x i The generated preparation base is By i The generated preparation base is Among them, θ is |0> and |1> represent the horizontal and vertical polarization of the photon, respectively.

3. A receiving device-independent quantum secure direct communication method according to claim 1, characterized in that: In step 2, the information receiver Alice randomly selects an integer x from the sequence {X} i The generation preparation base prepares 3r photons, and the quantum state of each photon is: The preparation sequences of the photons of sequences S1, S2, and S3 are {X1}, {X2}, and {X3}, respectively, and are described as: <h2 style=";text-align:left;direction:ltr">{X1} = {a1,a2,a3,......,a<h2 style=";text-align:left;direction:ltr"> r <h2 style=";text-align:left;direction:ltr">} <h2 style=";text-align:left;direction:ltr">{X2} = {b1,b2,b3,......,b<h2 style=";text-align:left;direction:ltr"> r <h2 style=";text-align:left;direction:ltr">} {X3}={c1,c2,c3,......,c r } where a r , b r 、c r is an integer xi randomly selected from the sequence {X}; Alice performs a random operation on the sequence S3 photons, described as: Among them, U0 and U1 represent the identity operation and phase flip operation respectively. After the U0 and U1 operations, the quantum state evolution of the photon is:

4. The receiving device-independent multi-party quantum secure direct communication method according to claim 1, characterized in that: The safety detection process in step 4 is as follows: After receiving all the photons, the communicating party Bob first stores the photons in the quantum memory. Then Alice announces the position of the photons in sequence S1. Bob extracts the photons of sequence S1 from the quantum memory and records the missing photons. In the sequence {Y} = {y1, y2, y3, ..., y n } randomly select y i Generate measurement basis |ψ y >, perform binary measurement after performing M operation, the M operation is described as: Here, y i It represents the i-th element in the sequence {Y}, where y represents the result of binary measurement. When y = 0, it means that after the M operation |ψ x > is projected onto If y=1, it means that after the M operation |ψ x >Not projected to When Bob performs the first round of security testing, the randomly selected preparation base composition sequence {Y1} is described as: <h2 style=";text-align:left;direction:ltr">{Y1} = {w1,w2,w3,......,w<h2 style=";text-align:left;direction:ltr"> r <h2 style=";text-align:left;direction:ltr">} where w r is an integer yi randomly selected from the sequence {Y}; Bob publishes the measurement basis and measurement results of each photon. Alice calculates the theoretical probability distribution of the measurement results based on the preparation basis and measurement basis of each photon, which is described as: If the probability distribution of Bob's measurement value deviates too much from the theoretical calculation, it is considered that the photon transmission process is unsafe or the receiving device is unsafe, and the communication is canceled. If the probability distribution of Bob's measurement value deviates within the allowable range, it is considered that there is no eavesdropping during the first round of photon transmission in the channel and Bob's receiving device is safe, and the next step is carried out.

5. The receiving device-independent quantum secure direct communication method according to claim 1, characterized in that: The two operators used for encoding in step 5 are: Among them, U0 and U1 represent the classical information 0 and 1 respectively; The preparation sequences {X2} and {X4} of the disrupted sequence S2 photons are described as: <h2 style=";text-align:left;direction:ltr">{X2} = {b1,b2,b3,......,b<h2 style=";text-align:left;direction:ltr"> r <h2 style=";text-align:left;direction:ltr">} {X4}={d1,d2,d3,......,d r } Among them, b r and d r Represents the preparation sequence element of the rth photon before and after scrambling.

6. A receiving device-independent quantum secure direct communication method according to claim 1, characterized in that: The safety detection process in step 6 is as follows: After Alice receives all the photons, she first stores them in the quantum memory. Then Bob announces the positions of the photons in the scrambled sequence S2. Alice extracts the photons of the scrambled sequence S2 from the quantum memory, records the missing photons, and measures them based on the measurement basis generated by the sequence {X2}, which can be described as: Where b represents the measurement result, b i represents the i-th element in the sequence {X2}; Bob announces the scrambled order of S2 photons, and Alice calculates the theoretical probability distribution of the measurement results based on the sequences {X2} and {X4}, which is described as: If the probability distribution of Alice's measurement value deviates too much from the theoretical calculation, the photon transmission process is considered unsafe and the communication is canceled. If the probability distribution of Bob's measurement value deviates within the allowable range, it means that there is no eavesdropping during the second round of photon transmission in the channel and Alice's receiving device is safe, so proceed to the next step.

7. The receiving device-independent quantum secure direct communication method according to claim 1, characterized in that: In step 7, Bob publishes the scrambled order of information transmission photons, Alice extracts all coded photons, performs binary measurement on all coded photons according to the sequence {X3}, and performs random operations on the sequence S3 to interpret the information transmitted by the communication party Bob, which is described as: in, Indicates that the c in the sequence {X3} i The single photon produced represents the photon used to transmit the classical information 0, represents the photon used to transmit the classical information 1, p(a=0) and p(a=1) represent the probabilities of measuring 0 and 1 respectively.

8. The receiving device-independent quantum secure direct communication method according to claim 1, characterized in that: The capacity of the channel is estimated to be: C s =I(B:A)-I(B:E) Among them, I(B:A) represents the mutual information between Bob and Alice, and I(B:E) represents the mutual information between Bob and Eve; I(B:A)=Q BAB [1-h(E BAB )] Among them, Q BAB E represents the total gain of Alice detecting the photon sent by Bob, that is, the probability of the detector response caused by the photon sent back by Bob at Alice after two rounds of photon transmission, BAB represents the total error rate of reading Bob's information from Alice, h(x) = -xlog2x-(1-x)log2(1-x) represents the binary Shannon entropy, is the gain of photons stolen by Eve in the first round of photon transmission when the number of photons is s; Among them, let the coupling coefficient between photons and optical fibers be η c , when photons are transmitted in the channel, the transmission efficiency η t =10 -aL / 10 L is the photon transmission distance, a = 0.2dB / kM, and the storage efficiency of quantum memory is η m , the detection efficiency of the photon detector is η d , Y0 is the probability of a dark count occurring in the detector, δθ and δx i is the error that occurs in the actual quantum channel, and μ is the average number of photons.

9. The receiving device-independent quantum secure direct communication method according to claim 1, characterized in that: The method can ensure that when the receiving device is a black box, information transmission is still absolutely safe, effectively enhancing the safety of QSDC under actual experimental conditions. The method only uses single photons and single photon measurements, and the signal photon preparation efficiency and detection efficiency are both high, that is, more than 90%.

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