Error performance for non-destructive quantum receiver of M-ary coherent-state signals

Recently, a capacity-achievable quantum collective decoding was proposed. The decoding appears optimal in the limit of an infinite number of signals. However, in the case of finite signals, the error performance is as yet unknown. In the present paper, we apply the idea of quantum collective decoding to the construction of a quantum receiver for M-ary coherent-state signals. We then calculate the error probability of the receiver, and show that its error performance is quasi-optimum.