A Poisson-Gaussian Noise Limited Quantum Iterative Multi-User System with Non-Ideal Photon-Counting Receiver

Coherent state quantum communication is attracting extensive attention for its great value in terrestrial and satellite information networks. This paper proposes a new non-orthogonal quantum multi-user (MU) iterative detection scheme. At the receiving end, we develop a composite quantum receiver with multi-stage measurement instrument and soft iterative MU detector. Furthermore, based on three-dimensional factor graph, a nonlinear Poisson-Gaussian noise limited coherent-state iterative MU parallel interference cancellation (PIC) algorithm is derived. Our results demonstrate that this system can well support MU communication and achieve good performance. Quantitatively, for the 8 users scenario, the BER of 10^{6} can be obtained when photon numbers is 19. Further numerical results show that the system we designed exhibits superior robustness against imperfections (e.g. quantum mode mismatch and quantum thermal noise).