Detection scheme for quantum multiple access channel with noisy coherent state

Quantum detection techniques based on multi-access quantum channel promise efficient quantum optimal solutions to quantum multi-user detection. "Discrete coherent state"(DCS) approximation method is a practical model for solving the mixed-state detection problem. Generally, the input states are pure states, while the output states are turned out to be mixed states corrupted by the noise in quantum channel. In this paper, we consider the detection scheme with DCS approximation in a quantum multiple access channel. We deduce the error probability of symbol rate of the detection algorithm with DCS detection scheme in multi-user detection fashion. By numerical simulations, we analyze and compare the performance of this detection scheme with different degree approximation. It is shown that this detection scheme is available for the quantum multi-user detection. For a normal noise, say jV=0.1, we will get the 10^-3 when number of photons Ns go to 18.