The optimum detection operators are derived for several linearly independent signal sets. The quantum minimax strategy is applied to the M-ary coherent state signals such as binary phase shift, ternary symmetric, ternary phase shift, and quadrature phase shift. It is shown that the detection process induces a kind of quantum interference between signal quantum states and measurement states. © 1996 The American Physical Society.

• Received 17 April 1996

DOI:https://doi.org/10.1103/PhysRevA.54.1691