A sparse quantum coherent state multi-user communication system based on partitioned detection

Abstract

The present invention belongs to the field of quantum communication technology, specifically a sparse quantum coherent state multi-user communication system based on partition detection. The present invention 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; the receiving end includes a partition detection quantum receiving module and a multi-user decoding module; the present invention sets a switch at the transmitting end to realize sparse processing of multi-user transmitted signals, which can reduce multi-user interference and improve the quality of the communication system; 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 according to the measurement results of the current partition, thereby improving the detection and decoding accuracy; the system of the present invention has strong resistance to multi-user interference, fast system convergence speed, and good 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 convergence of the Internet of Things (IoT) and 5G and 6G is driving the realization of faster and more reliable communication systems, while also placing greater demands and higher requirements on the performance of these systems. Traditional communication technologies face a range of challenges, such as information security and limited transmission rates. At the same time, information technology based on classical communication theory is gradually approaching the Standard Quantum Limit (SQL). Within the framework of classical communication theory, the only way to continuously approach this performance limit is through various technical strategies. To push the performance envelope, scientists have rationally generalized classical communication theory. Quantum communication technology, based on the properties of quantum mechanics, has become a key technology for resolving the performance challenges of traditional communication systems. This provides a new perspective for building novel communication systems and offers new research directions for the efficiency and security of future communication systems. Scientists have discovered that the error rate performance of quantum communication systems can exceed the SQL and reach a new limit—the Helstrom limit.

[0003] Designing a physically feasible quantum receiver and corresponding iterative detection algorithm for communication systems that gradually approaches the Helstrom limit has become a major focus for researchers. The Kennedy receiver was the first proposed quantum receiver, and its performance can surpass the SQL at large photon numbers. However, it still lags significantly behind the Helstrom limit. The Dolinar receiver is the first structured receiver to theoretically reach the Helstro limit using physically feasible measurements and real-time optical feedback. However, this receiver requires precise local laser intensity control, making its practical implementation at high data rates challenging. Subsequently, various quantum receivers and detection and decoding algorithms have been proposed and experimentally verified, but none have achieved both superior performance and low complexity. Partitioned detection quantum receivers, on the other hand, achieve flexible control of reception performance by optimizing partitioning strategies, thereby improving overall system efficiency. When combined with a suitable detection and decoding algorithm, they can achieve satisfactory reception performance while maintaining low computational complexity.

[0004] Non-Orthogonal Multiple Access (NOMA) technology enables multiple users to simultaneously access the same frequency band or coding resources in a non-orthogonal manner, supporting large-scale connections and flexible user access, thereby improving spectrum utilization and system capacity. Similar to classical communications, multi-user access technology in quantum communications is also key to improving system performance. However, current quantum communication research mostly focuses on quantum receiver design in single-user communication systems, with less involvement in multi-user scenarios. Even in cases involving multiple users, they often face severe 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 present invention provides a sparse quantum coherent state multi-user communication system based on a partitioned detection receiver, comprising 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 partitioned 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 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 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 bits are sent or not, thereby achieving the sparseness of the coding sequence and obtaining the sparse sequence z k ; The sparse mapping module is also called the 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 partitioned detection quantum receiving module receives signals transmitted from free space and divides the received signals into N partitioned signals using N-1 beam splitters. Within each partition, the signal is displaced by the local oscillator field, and then the superposition field is detected by photons using a photon detector. The local oscillator field of the nth partition is updated and calculated based on the detection results transmitted from the previous partition.

[0014] The multi-user decoding module, within each partition, uses a quantum multi-user iterative detection algorithm for decoding. This algorithm, based on the Turbo principle, transmits and feeds back external information between two soft-input and soft-output modules to achieve separate decoding of multi-user signals.

[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] (1) At the transmitting end,

[0018] (1) In the channel coding module, for the kth user, the information bits it sends 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 takes a value of 0 or 1, and Ld represents the length of the information bit sequence. In order to correspond to the quantum coherent state signals |α> and |-α>, the present invention maps bit 0 to -1 through the 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 π 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 transmitted signal. The state information of the transmitter switch is provided at the receiving end, so the switch information is known to the receiving algorithm. The moment when no symbols are transmitted is called the "idle" state.

[0021] In the sparse pattern mapping unit, the switch and interleaver depths are the same, ensuring that at least one chip per bit of information remains in the "closed" state. Otherwise, that bit of information cannot be transmitted, resulting in an increase in the system bit error rate (BER). Furthermore, the sparsity cannot be less than the repetition code rate, otherwise some bits of information will inevitably be unable 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 of s 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, which is 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 and is transmitted.

[0032] (2) At the receiving end:

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

[0034] The transmission signal states of K users are binary phase shift keying (BPSK) coherent state signals and "idle". 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. 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 after N-1 is τ 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 used to perform the displacement operation; when n>1, the local oscillator field signal is:

[0053]

[0054] After the shift, 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 detection efficiency of the detector, n b The number of photons counted for background light darkness.

[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 transferred to the nth partition and iterated as the prior probability:

[0062]

[0063] After all N partitions are 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, s k [j] = 0, corresponding posterior information External Information

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

[0069]

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

[0071]

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

[0073]

[0074] Q 1,n represents z k,n Average light intensity under [j] = +1:

[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, 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, which can reduce multi-user interference and improve the quality of the communication system.

[0081] (2) A partitioned detection quantum receiver is used at the receiving end, and a multi-user soft detection decoding algorithm is designed in combination with iterative interference cancellation. The receiving end updates the local oscillator field signal in the next partition based on the measurement results of the current partition, 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 This is a diagram of the transmitting end structure of the sparse quantum coherent state multi-user communication system based on partition detection of the present invention.

[0084] Figure 2 Schematic diagram of sparse NOMA signal transmission in the present invention.

[0085] Figure 3 This is a diagram of the receiving end structure 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 of the system proposed in the present invention and the non-sparse system based on Kennedy receiver.

[0087] Figure 5 This is a graph showing how the system bit error rate proposed in the present invention changes with the number of partitions. DETAILED DESCRIPTION

[0088] The present invention is further described below through 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, and the information d k After bit mapping and channel coding, the mapping sequence c is obtained k and coding sequence u k , and then each user's unique interleaver π k Random interleaving generates interleaved sequence x k In the sparse mapping module, the encoding 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 sent into free space for transmission.

[0090] like Figure 2 Figure 1 shows a simple schematic diagram of sparse NOMA signal transmission. The initial information sequence for four users is first encoded with a 1 / 4 rate repetition code, then deorthogonalized by an interleaver to form a NOMA sequence. A switch is then used to retain half of the repetitions in the NOMA sequence, resulting in "1 / 2 sparseness." Retaining 1 / 4 of the repetitions in the NOMA sequence results in "1 / 4 sparseness."

[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 from 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 . Use the Gamma-Gamma distribution containing double random numbers to represent I, 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 consists of two parts: a partition detection quantum receiver and a multi-user signal decoding unit. Figure 3 The figure shows the receiver architecture of the sparse quantum coherent state NOMA communication system based on partitioned detection. The partitioned detection receiver shifts the partitioned signal to the vacuum state through a shift operation, minimizing detection errors. Therefore, if the switching information is known, there is no need to detect the "idle" state of the transmitter.

[0098] In the partitioned detection and receiving module, the received signal is divided into N partitioned signals by N-1 beam splitters. Within each partition, the signal is shifted by the local oscillator field, and then the superposition field is detected by photon detectors. The local oscillator field of the nth partition is updated based on the detection results transmitted from the previous partition.

[0099] Within each partition, the quantum multi-user iterative detection algorithm proposed in this paper is used for decoding. This algorithm, based on the Turbo principle, transmits and feeds external information between the internal soft-output module and the external soft-output module to achieve separation and decoding of multi-user signals.

[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 each channel {I 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 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 partitioned detection. Figure 4 The exit diagrams for a quantum communication system based on a partitioned detection receiver with N=2 partitions and a quantum communication system based on a traditional Kennedy receiver are presented. It can be seen that the proposed system converges after five iterations, reaching a convergence point of (1.00, 0.98), while the traditional Kennedy receiver-based quantum communication system converges after six iterations, reaching a convergence point of (0.99, 0.83). This demonstrates that the proposed quantum communication system achieves a lower bit error rate and faster convergence after iterations.

[0104] Figure 5 A graph showing the bit error rate of a sparse quantum coherent state multi-user communication system based on partition detection as a function of the number of partitions is presented, as well as the bit error rate of a quantum multi-user communication system based on a Kennedy receiver. This graph clearly shows that the bit error rate of the system proposed in the present invention is significantly related to the number of partitions. As the number of partitions increases, the system bit error rate gradually decreases. This is because the larger the number of partitions, the more accurate the estimation of the local oscillator field and the higher the photon detection accuracy. Furthermore, 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, demonstrating the superior 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 solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. A sparse quantum coherent state multi-user communication system based on a partitioned detection receiver, characterized in that: It includes a transmitting end and a receiving 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 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 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 bits are sent or not, thereby achieving the sparseness of the coding sequence and obtaining the sparse sequence z k ; The coherent state modulation module converts the sparse sequence z k Modulate it into a quantum coherent state signal and then send it into free space for transmission; On the receiving end: The partition detection quantum receiving module receives the signal transmitted from free space and divides the received signal into N partition signals using N-1 beam splitters. Within each partition, the signal is displaced by the local oscillator field, and then the superposition field is detected by photons using a photon detector. The local oscillator field of the nth partition is updated and calculated based on the detection result transmitted from the previous partition. The multi-user decoding module, i.e., within each partition, uses a quantum multi-user iterative detection algorithm for decoding. This algorithm, based on the Turbo principle, transmits and feeds back external information between two soft-input and soft-output modules, thereby completing the separation and decoding of multi-user signals. 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.

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, the information bits it sends 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 Indicates the length of the information bit sequence; in order to correspond to the quantum coherent state signals |α and |-α>, bit 0 is mapped to -1 through the 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.

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 status of the user's information at a specific time, thereby achieving sparse transmission of the signal; The switcher has the same depth as the interleaver and ensures that at least one chip per bit of information remains 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 status 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, which is 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 and is transmitted.

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 the vacuum state through a shift operation to minimize the detection error; for the "idle" state of the transmitting end, if the switch information is known, there is no need to detect it; The transmission signal states of K users are binary phase-shift keying coherent state signals and "idle" respectively. 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. 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, with the unit set to meters; The transmittance after N-1 is τ 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 ; 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 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 the photons in the nth partition, and r n The probability of [j] photons follows a Poisson distribution: Where η is the detection efficiency of the detector, n b The number of photons counted for background light 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 transferred to the nth partition and iterated as the prior probability: After all N partitions are 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, s k [j] = 0, corresponding posterior information External Information when When, s k [j] = 1, r is received in the nth partition n The posterior information corresponding to [j] photons is: The external information expression of the quantum soft interference elimination multi-user decoding algorithm based on partitioned detection reception is: Among them, Q 0,n represents z k,n Average light intensity of [j] = -1: Q 1,n represents z k,n Average light intensity under [j] = +1: 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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