Sparse quantum coherent state multi-user communication system based on partition detection

Abstract

The invention belongs to the technical field of quantum communication, and particularly relates to a sparse quantum coherent state multi-user communication system based on partition detection. The system comprises a transmitting end and a receiving end, the transmitting end comprises a channel coding module, a signal interleaving module, a sparse mapping module and a coherent state modulation module; the receiving end comprises a partition detection quantum receiving module and a multi-user decoding module; according to the method, the switch is arranged at the transmitting end, so that sparse processing of multi-user transmitting signals is realized, multi-user interference can be reduced, and the quality of a communication system is improved; a partition detection quantum receiver is adopted at a receiving end, and a multi-user soft detection decoding algorithm is designed in combination with iterative interference cancellation; the receiving end updates the local oscillation field signal in the next partition according to the measurement result of the current partition, so that the detection and decoding accuracy is improved; the system disclosed by the invention is high in multi-user interference resistance, high in convergence speed and good in robustness.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum communication, and in particular relates to a sparse quantum coherent state multi-user communication system based on partition detection. Background Art

[0002] The integrated development of the Internet of Things and 5G and 6G has promoted the realization of faster and more reliable communication systems, and has also put forward more demands and higher requirements on the performance of communication systems. Traditional communication technologies face a series of challenges, such as information security and limited transmission rate. At the same time, information technology based on classical communication theory has gradually approached the Standard Quantum Limit (SQL). Under the framework of classical communication theory, we can only continue to move closer to the performance limit through various technical strategies. In order to break through the performance limit of the system, scientists have made reasonable promotions of classical communication theory. Quantum communication technology based on the characteristics of quantum mechanics has become a key technology to solve the performance dilemma of traditional communication systems, providing a new perspective for building new communication systems, and also providing a new research direction for the efficiency and security of future communication systems. Scientists have found that the error performance of quantum communication systems can break through SQL and reach a new limit-the Helstrom limit.

[0003] How to design a quantum receiver that is physically feasible and gradually approaches the Helstrom limit in a communication system and the corresponding iterative detection algorithm has become the focus of attention of many researchers. The Kennedy receiver is the earliest proposed quantum receiver. When the number of photons is large, its performance can exceed SQL. However, compared with the Helstrom limit, there is still a significant gap. The Dolinar receiver is the first structured receiver that theoretically reaches the Helstro limit using physically feasible measurements and real-time optical feedback. However, this receiver requires precise local laser intensity control, and its actual implementation at high data rates is challenging. Subsequently, a variety of quantum receivers and detection and decoding algorithms have been proposed and experimentally verified, but none of them have achieved both superior performance and low complexity. The partition detection quantum receiver optimizes the partition strategy to achieve flexible control of the receiving performance, thereby improving the overall efficiency of the system. When combined with a suitable detection and decoding algorithm, it can achieve satisfactory receiving performance while having low computational complexity.

[0004] Non-Orthogonal Multiple Access (NOMA) technology enables multiple users to access the same frequency band or coding resources simultaneously in a non-orthogonal manner, supports large-scale connections and flexible user access, and thus improves spectrum utilization and system capacity. Similar to classical communications, multi-user access technology in quantum communications is also the key to improving system performance. However, current quantum communication research mostly focuses on the design of quantum receivers in single-user communication systems, and rarely involves multi-user scenarios. Even if there are cases involving multiple users, they often face serious multi-user interference and high decoding complexity. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a sparse quantum coherent state multi-user communication system based on partition detection with strong anti-interference ability, fast convergence speed and good robustness.

[0006] The sparse quantum coherent state multi-user communication system based on a partition detection receiver provided by the present invention comprises a transmitting end and a transmitting end; the transmitting end comprises a channel coding module, a signal interleaving module, a sparse mapping module and a coherent state modulation module, and the receiving end comprises a partition detection quantum receiving module and a multi-user decoding module; wherein:

[0007] On the transmitter side:

[0008] The channel coding module transmits the information d of the kth user at the transmitting end. k After bit mapping and channel coding respectively, the mapping sequence c is obtained k and the coding sequence u k , k = 1, 2, ... K, K is the total number of sending users;

[0009] The signal interleaving module obtains a mapping sequence c for the channel coding module k and the coding sequence u k Through the user's corresponding interleaver Π k Random interleaving generates non-orthogonal interleaved sequence x k ;

[0010] The sparse mapping module uses a switch to control whether the signal bit is sent or not, thereby achieving sparseness of the coded sequence and obtaining a sparse sequence z k ; The sparse mapping module is also called a sparse pattern mapping unit;

[0011] The coherent state modulation module converts the sparse sequence z k It is modulated into a quantum coherent state signal and then sent into free space for transmission.

[0012] On the receiving end:

[0013] The partition detection quantum receiving module receives the signal transmitted from the free space, and divides the received signal into N partition signals by N-1 beam splitters; in each partition, the signal is displaced under the action of the local oscillator field, and then the superposition field is photon detected by a photon detector; wherein the local oscillator field of the nth partition is updated and calculated according to the detection result transmitted from the previous partition.

[0014] The multi-user decoding module, i.e., in each partition, uses a quantum multi-user iterative detection algorithm for decoding. This algorithm is based on the Turbo principle and completes the separation and decoding of multi-user signals by transmitting and feeding back external information between two soft-input and soft-output modules.

[0015] When the last iteration of the Nth partition is completed, the system converges. At this time, a hard decision is made on the output a posteriori information to obtain the decoded value of each user information.

[0016] Further:

[0017] (a) At the transmitting end,

[0018] (1) In the channel coding module, for the kth user, its transmitted information bits are d k ={d k [i],i=1,2,...,L d ; k∈[1,K]}, where d k [i] represents the i-th information bit, which can be 0 or 1, and Ld represents the length of the information bit sequence. To facilitate the correspondence with the quantum coherent state signals |α> and |-α>, the present invention maps bit 0 to -1 through a symbol mapping unit, and bit 1 is still mapped to 1, and the sequence c is obtained. k ={c k [i],i=1,2,...,L d}. After that, the channel coding module generates the coding sequence u k = {u k [j],j∈[1,L u ]},L u is the length of the encoding sequence.

[0019] (2) In the signal interleaving module, each user has a unique interleaver II. k , the interleaver interleaves the coded sequence to generate a non-orthogonal sequence x k ={x k [j]}.

[0020] (3) In the sparse mapping module, a switch is set for each user to control the transmission status of the user's information at a specific time, thereby achieving sparse transmission of the signal. The state information of the transmitter switch is provided at the receiving end, so the switch information is known in the receiving algorithm. The moment when no symbol is transmitted is called the "idle" state.

[0021] In the sparse pattern mapping unit, the switch and interleaver have the same depth, and ensure that at least one chip is kept in the "closed" state for each bit of information, otherwise the bit of information will not be transmitted, resulting in an increase in the system bit error rate (BER). In addition, the sparsity cannot be less than the repetition code rate, otherwise some bits of information will inevitably fail to be transmitted.

[0022] The interleaved sequence enters the sparse pattern mapping unit, where z is obtained k ={z k [j] = s k [j]·x k [j]}. Specific use k [j] represents the on / off status of the user’s switch at time j. k When [j] = 1, the switch is in the "closed" state and the signal is sent; when s k When [j] = 0, the switch is in the "open" state and the signal cannot be sent. Therefore, there are three signal states for channel transmission: "|-α>", "|α>" and "idle" where no symbol is transmitted; k [j] Possible values ​​are:

[0023]

[0024] (4) In the coherent state modulation module, the sparse sequence enters the coherent state modulation unit and is modulated into a quantum coherent state:

[0025] α k >={|z k [j]·α>,j∈[1,L u ]}, (2)

[0026] Among them, |α> is a coherent state, defined as the annihilation operator in the quantum light field. The eigenstates of :

[0027] α represents the corresponding eigenvalue, the annihilation operator It is a non-Hermitian operator and cannot be directly observed, so its eigenvalues ​​are usually complex numbers.

[0028] The coherent state |α> can be expressed as a coherent superposition of the photon number state |n>:

[0029]

[0030] The average number of photons in the coherent state |α> If |α 2 =0, indicating that the number of photons is 0, corresponding to the vacuum state |0>.

[0031] The modulated quantum coherent state signal enters the free space for transmission.

[0032] (ii) At the receiving end:

[0033] (1) In the partition detection quantum receiving module, the partition signal is shifted to the vacuum state through the displacement operation to minimize the detection error. Then, for the "idle" state of the transmitting end, under the condition of known switch information, it is not necessary to detect it.

[0034] The transmission signal states of K users are binary phase shift keying (BPSK) coherent state signal and "idle". Among them, the coherent state signal set is {|α>,|-α>}. The signal is expressed as:

[0035]

[0036] The symbol I is used to represent the channel coefficient. The channel coefficient of the kth user is I k After being transmitted through the free space channel, it reaches the receiving end, and the received signal at time j is:

[0037]

[0038] The present invention uses a Gamma-Gamma distribution containing double random numbers to represent I, and its probability density function is:

[0039]

[0040] Γ(·) is the Gamma function, K n (·) is the modified nth-order Bessel function of the second kind, α c and β c is the flicker parameter, and α c >0,β c >0, the calculation expression is:

[0041]

[0042] in, is the Rytov variance, Refers to the refractive index, k = 2π / λ refers to the light wave factor, λ refers to the wavelength, d = (kD 2 / 4L) 12is the geometric factor, D is the diameter of the receiving aperture, and L is the link distance, usually in meters.

[0043] The transmittance is τ through N-1 n The beam splitter is divided into N equal partitions, and the partition signal is:

[0044]

[0045] β m > can be expressed as the direct product of N partition signals:

[0046]

[0047] The transmittance of the beam splitter is:

[0048]

[0049] In the nth partition, the receiver first performs a shift operation, signal |β m,n >Local Oscillator Field The average field strength of the superposition field in units of photons is expressed as:

[0050]

[0051] Among them, ξ∈(0,1] is the mode mismatch coefficient between the local oscillator field and the signal field, τ n ∈(0,1] is the transmittance of the beam splitter.

[0052] When n=1, the local oscillator field signal can be randomly assumed to be a certain signal field, and the signal field can be used to perform the displacement operation; when n>1, the local oscillator field signal is:

[0053]

[0054] After the displacement, the photon number is counted in the nth partition using a single photon number resolving detector (PNRD) to detect r n The probability of [j] photons follows a Poisson distribution:

[0055]

[0056] Where η is the detector detection efficiency, n b The number of photons counted for background light.

[0057] When calculating the local oscillator field of each zone, m * The value of can be determined according to the maximum a posteriori probability criterion:

[0058]

[0059] p post_m,n The posterior probability of detecting r[j] photons in the nth partition is calculated by the Bayesian criterion:

[0060]

[0061] The posterior probability of the signal of the n-1th partition is passed to the nth partition and iterated as the prior probability:

[0062]

[0063] After all N partitions have been detected, the maximum a posteriori criterion is used to make the final decision of the receiver.

[0064] (2) In the multi-user decoding module, the quantum multi-user iterative detection decoding algorithm is specifically:

[0065] make The signal received by the nth partition is:

[0066]

[0067] when When k [j] = 0, corresponding posterior information External Information

[0068] when When k [j] = 1. In the nth partition, r is received n The a posteriori information corresponding to [j] photons is:

[0069]

[0070] The external information expression of the quantum soft interference elimination multi-user decoding algorithm based on partition detection reception is:

[0071]

[0072] Among them, Q 0,n Indicates z k,n Average light intensity of [j] = -1:

[0073]

[0074] Q 1,n Indicates z k,n [j] = average light intensity under +1 conditions:

[0075]

[0076] nest,k,n with n' est,k,n They are the interference between multi-user information:

[0077]

[0078] Before the first iteration of the first partition, initialize the prior probability p a_1,1 =p a_0,1 =0.5, prior information In the first iteration of the nth partition, the prior information By outputting the external information of the last iteration of the previous partition After the last iteration of the Nth partition is completed, a hard decision is made on the last output a posteriori information to obtain the decoding value for each user information sequence.

[0079] The technical features of the present invention mainly include:

[0080] (1) The present invention sets a switch at the transmitting end to implement sparse processing of multi-user transmitted signals in a low-complexity method, thereby reducing multi-user interference and improving the quality of the communication system.

[0081] (2) A partition detection quantum receiver is used at the receiving end, and a multi-user soft detection decoding algorithm is designed in combination with iterative interference elimination. The receiving end updates the local oscillator field signal in the next partition based on the measurement results of the current partition, thereby improving the detection and decoding accuracy.

[0082] (3) Compared with the multi-user communication system under the classical theoretical framework, the present invention can break through the standard quantum limit SQL, improve system performance, and has good robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 The figure is a diagram of the structure of the transmitter of the sparse quantum coherent state multi-user communication system based on partition detection of the present invention.

[0084] Figure 2 This is a schematic diagram of sparse NOMA signal transmission according to the present invention.

[0085] Figure 3 The diagram is a structural diagram of the receiving end of the sparse quantum coherent state multi-user communication system based on partition detection of the present invention.

[0086] Figure 4 This is an EXIT comparison diagram between the system proposed in the present invention and the non-sparse system based on Kennedy receiver.

[0087] Figure 5 This is a curve diagram showing the system bit error rate proposed by the present invention as the number of partitions changes. DETAILED DESCRIPTION

[0088] The present invention is further described below by way of embodiments in conjunction with the accompanying drawings.

[0089] like Figure 1 As shown in the figure, the transmitter of the sparse quantum coherent state multi-user communication system based on partition detection is set to have K users, sending information d k After bit mapping and channel coding, the mapping sequence c is obtained k and the coding sequence u k , and then each user's unique interleaver Π k Random interleaving generates an interleaved sequence x k In the sparse mapping module, the encoded sequence is sparsely mapped to obtain a sparse sequence z k . Then, the sparse sequence z k It enters the coherent state modulation module, is modulated into a quantum coherent state signal, and then is sent into free space for transmission.

[0090] like Figure 2 As shown in the figure, a simple schematic diagram of sparse NOMA transmission signal is given. The initial information sequence with 4 users is first encoded with a 1 / 4 code rate repetition code, and then non-orthogonalized by an interleaver to form a NOMA sequence. Then, half of the repetition sequence in the NOMA sequence is retained with the help of a switch, which is "1 / 2 sparse"; if 1 / 4 of the repetition sequence in the NOMA sequence is retained, it is "1 / 4 sparse".

[0091] In this embodiment, the system sparsity is selected as 1 / 2, the number of users is 4, and the frame length of each user information bit is 2. 10 =1024 bits, the number of frames is 100, and the average information bit energy of the user is recorded as E b , in dBJ, the number of background noise photons n b Includes the number of photons of background light and dark current.

[0092] In this embodiment, the symbol I is used to represent the channel coefficient. The channel coefficient of the kth user is I k . I is represented by a Gamma-Gamma distribution containing double random numbers, and its probability density function is:

[0093]

[0094] Γ(·) is the Gamma function, K n (·) is the modified nth-order Bessel function of the second kind, α c and β c is the flicker parameter, and α c >0,

[0095] β c >0.

[0096] In this embodiment, the flicker coefficient α of the Gamma-Gamma turbulent fading is set c =4 and β c =1, the wavelength of the light source is set to 0.4um, and the diameter of the receiving hole is set to 2cm.

[0097] In this embodiment, the receiving end mainly includes two parts, namely a partition detection quantum receiver and a multi-user signal decoding. Figure 3 The figure shows the receiving end structure of the sparse quantum coherent state NOMA communication system based on partition detection of the present invention. The partition detection receiver shifts the partition signal to the vacuum state through the shift operation to minimize the detection error. Then, for the "idle" state of the transmitter, under the condition of known switch information, it is not necessary to detect it.

[0098] In the partition detection receiving module, the received signal is divided into N partition signals by N-1 beam splitters. In each partition, the signal is displaced under the action of the local oscillator field, and then the superposition field is photon detected using a photon detector. Among them, the local oscillator field of the nth partition is updated and calculated based on the detection result transmitted from the previous partition.

[0099] Within each partition, the quantum multi-user iterative detection algorithm proposed in the present invention is used for decoding. This algorithm is based on the Turbo principle and completes the separation and decoding of multi-user signals by transmitting and feeding back external information between the internal soft module and the external soft module.

[0100] In the first iteration of the first partition, the prior probability p is initialized a_1,1 =p a_0,1 =0.5, prior information In the first iteration of the nth partition, the prior information By outputting the external information of the last iteration of the previous partition After the last iteration of the Nth partition is completed, the system converges, and a hard decision is made on the output a posteriori information to obtain the decoded value of each user information.

[0101] To ensure the fading between channels k ,k∈[1,K]} are independent of each other, and the distance between each receiving end is set far enough to exceed the coherence distance. The number of photons counted by background light and dark light is n b Set to 30 photons / bit.

[0102] Set the system parameters to the ideal value: η = 1.0, τ = 1.0, n b =30,ξ=1.0.

[0103] In this embodiment, an extrinsic information transfer (EXIT) diagram is used to analyze and evaluate the convergence performance of a sparse quantum coherent state multi-user communication system based on partition detection. Figure 4 The EXIT diagrams of the quantum communication system based on the partition detection receiver when the number of partitions N=2 and the quantum communication system based on the traditional Kennedy receiver are respectively given. It can be seen that the system proposed by the present invention converges after 5 iterations, and the convergence point is (1.00, 0.98), while the traditional quantum communication system based on the Kennedy receiver converges after 6 iterations, and the convergence point is (0.99.0.83). This shows that the quantum communication system proposed by the present invention has a lower bit error rate and a faster convergence speed after iteration.

[0104] Figure 5 A curve diagram showing the bit error rate of a sparse quantum coherent state multi-user communication system based on partition detection as the number of partitions changes is given, as well as the bit error rate of a quantum multi-user communication system based on a Kennedy receiver. It can be clearly seen from this figure that the bit error rate of the system proposed in the present invention has a significant relationship with the number of partitions. As the number of partitions increases, the system bit error rate gradually decreases. The reason is that the larger the number of partitions, the more accurate the estimation of the local oscillator field, and the higher the photon detection accuracy. And when the number of partitions is the minimum value of 2, the bit error rate of the system proposed in the present invention is still lower than that of the quantum multi-user communication system based on the Kennedy receiver, proving the superiority of the performance of this system.

[0105] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A sparse quantum coherent state multi-user communication system based on partitioned detection receiver, characterized in that: It includes a transmitting end and a transmitting end; the transmitting end includes a channel coding module, a signal interleaving module, a sparse mapping module and a coherent state modulation module, and the receiving end includes a partition detection quantum receiving module and a multi-user decoding module; wherein: On the transmitter side: The channel coding module transmits the information d of the kth user at the transmitting end. k After bit mapping and channel coding respectively, the mapping sequence c is obtained k and the coding sequence u k , k = 1, 2, ... K, K is the total number of sending users; The signal interleaving module processes the mapping sequence c obtained by the channel coding module. k and the coding sequence u k Through the user's corresponding interleaver Π k Random interleaving generates non-orthogonal interleaved sequence x k ; The sparse mapping module uses a switch to control whether the signal bit is sent or not, thereby achieving sparseness of the coded sequence and obtaining a sparse sequence z k ; The coherent state modulation module converts the sparse sequence z k Modulate into quantum coherent state signal and then send into free space for transmission; On the receiving end: The partition detection quantum receiving module receives the signal transmitted from the free space, and divides the received signal into N partition signals by N-1 beam splitters; in each partition, the signal is displaced under the action of the local oscillator field, and then the superposition field is photon detected by a photon detector; wherein the local oscillator field of the nth partition is updated and calculated according to the detection result transmitted from the previous partition; The multi-user decoding module, i.e., in each partition, uses a quantum multi-user iterative detection algorithm for decoding; this algorithm is based on the Turbo principle and completes the separation and decoding of multi-user signals by transmitting and feeding back external information between two soft-input and soft-output modules; When the last iteration of the Nth partition is completed, the system converges, and a hard decision is made on the output a posteriori information to obtain the decoded value of each user information.

2. The sparse quantum coherent state multi-user communication system according to claim 1, characterized in that: In the channel coding module, for the kth user, its transmitted information bits are d k ={d k [i],i=1,2,...,L d ; k∈[1,K]}, where dk[i] represents the i-th information bit, which takes the value of 0 or 1, L d represents the length of the information bit sequence; in order to correspond to the quantum coherent state signals |α and |-α>, the bit 0 is mapped to -1 through the symbol mapping unit, and the bit 1 is still mapped to 1, and the sequence c is obtained. k ={c k [i],i=1,2,...,L d }; After that, the channel coding module generates the coding sequence u k = {u k [j],j∈[1,L u ]},L u is the length of the encoding sequence.

3. The sparse quantum coherent state multi-user communication system according to claim 2, characterized in that: In the signal interleaving module, each user has a unique interleaver PI k , the interleaver interleaves the coded sequence to generate a non-orthogonal sequence x k ={x k [j]}.

4. The sparse quantum coherent state multi-user communication system according to claim 3, characterized in that: In the sparse mapping module, a switch is set for each user to control the sending state of the user's information at a specific time to achieve sparse transmission of the signal; The switch has the same depth as the interleaver and ensures that at least one chip per bit of information is kept in the "closed" state. In addition, the sparsity cannot be less than the repetition code rate. The interleaved sequence enters the sparse pattern mapping unit and gets z k ={z k [j] = s k [j]·x k [j]}; specific use s k [j] represents the on / off state of the user’s switch at time j; when s k When [j] = 1, the switch is in the "closed" state and the signal is sent; when s k When [j] = 0, the switch is in the "open" state and the signal cannot be sent; therefore, there are three signal states for channel transmission: "|-α>", "|α>" and "idle" where no symbol is transmitted; k [j] Possible values ​​are:

5. The sparse quantum coherent state multi-user communication system according to claim 4, characterized in that: In the coherent state modulation module, the sparse sequence enters the coherent state modulation unit and is modulated into a quantum coherent state: a k >={|z k [j]·α>,j∈[1,L u ]}, (2) Among them, |α> is a coherent state, defined as the annihilation operator in the quantum light field. The eigenstates of : α represents the corresponding eigenvalue, the annihilation operator is a non-Hermitian operator whose eigenvalues ​​are complex; The coherent state |α> can be expressed as a coherent superposition of the photon number state |n>: The average number of photons in the coherent state |α> If |α| 2 =0, indicating that the number of photons is 0, corresponding to the vacuum state |0>; The modulated quantum coherent state signal enters the free space for transmission.

6. The sparse quantum coherent state multi-user communication system according to claim 5, characterized in that: In the partition detection quantum receiving module, the partition signal is shifted to a vacuum state through a displacement operation to minimize the detection error; for the "idle" state of the transmitting end, under the condition of known switch information, it is not necessary to detect it; The transmission signal states of K users are binary phase shift keying coherent state signal and "idle" respectively; among them, the coherent state signal set is {α>,|-α>}, and the signal is expressed as: The symbol I is used to represent the channel coefficient. The channel coefficient of the kth user is I k ; After being transmitted through the free space channel, it reaches the receiving end, and the received signal at time j is: Use the Gamma-Gamma distribution containing double random numbers to represent I, and its probability density function is: Γ(·) is the Gamma function, K n (·) is the modified nth-order Bessel function of the second kind, α c and β c is the flicker parameter, and α c >0,β c >0, the calculation expression is: in, is the Rytov variance, Refers to the refractive index, k = 2π / λ refers to the light wave factor, λ refers to the wavelength, d = (kD 2 / 4L) 12 is the geometric factor, D is the diameter of the receiving aperture, and L is the link distance, which is set in meters; The transmittance is τ through N-1 n The beam splitter is divided into N equal partitions, and the partition signal is: β m >Expressed as the direct product of N partition signals: The transmittance of the beam splitter is: In the nth partition, the receiver first performs a shift operation, signal |β m,n >Local Oscillator Field The displacement is caused by the action of photons; the average field strength of the superposition field in units of photons is expressed as: Among them, ξ∈(0,1] is the mode mismatch coefficient between the local oscillator field and the signal field, τ n ∈(0,1] is the transmittance of the beam splitter; When n=1, the local oscillator field signal can be randomly assumed to be a certain signal field, and the signal field can be used to perform the displacement operation; when n>1, the local oscillator field signal is: After the displacement, the single photon number resolution detector is used to count photons in the nth partition, and r n The probability of [j] photons follows a Poisson distribution: Where η is the detector detection efficiency, n b The number of photons counted for background light and darkness; When calculating the local oscillator field of each zone, m * The value of is determined according to the maximum a posteriori probability criterion: p post_m,n The posterior probability of detecting r[j] photons in the nth partition is calculated by the Bayesian criterion: The posterior probability of the signal of the n-1th partition is passed to the nth partition and iterated as the prior probability: After all N partitions have been detected, the maximum a posteriori criterion is used to make the final decision of the receiver.

7. The sparse quantum coherent state multi-user communication system according to claim 6, characterized in that: In the multi-user decoding module, the quantum multi-user iterative detection decoding algorithm is specifically: make The signal received by the nth partition is: when When k [j] = 0, corresponding posterior information External Information when When k [j] = 1, r is received in the nth partition n The a posteriori information corresponding to [j] photons is: The external information expression of the quantum soft interference elimination multi-user decoding algorithm based on partition detection reception is: Among them, Q 0,n Indicates z k,n Average light intensity of [j] = -1: Q 1,n Indicates z k,n [j] = average light intensity under +1 conditions: n est,k,n with n' est,k,n They are the interference between multi-user information: Before the first iteration of the first partition, initialize the prior probability p a_1,1 =p a_0,1 =0.5, prior information In the first iteration of the nth partition, the prior information By outputting the external information of the last iteration of the previous partition After the last iteration of the Nth partition, a hard decision is made on the last output a posteriori information to obtain the decoding value for each user information sequence.

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