Realization of quantum receiver for M-ary signals

In quantum communication theory, a realization of the optimum quantum recei ver that minimizes the error probability is one of fundamental problems. A quantum error cr is described by detection operators. Therefore, it is very important to derive the optimum detection operators for a realization of t he optimum quantum receiver. Irt general, it is difficult to derive the opt imum detection operators, except fur some simple casts. In addition, even i f we could derive the optimum detection operators, it is not trivial what d evice corresponds to the operators. In this paper, we show a realization me thod of a quantum receiver which is described by a projection-valued measur e (PVM) and apply the method to 3-ary phase-shift-keyed (3PSK) coherent-sta te signals.