A scheme for distinguishing between binary signals of nonorthogonal coherent states with the minimum average error is proposed. In contrast to the well-known Dolinar scheme, it does not use a feedback process. Instead, it achieves the same minimum error bound by only unitary transformations and photon number counting. It is shown that the required transformation should produce the appropriate Schrödinger-cat states. An example of the Hamiltonian generating such a process is derived from a multiphoton nonlinear optical process. © 1996 The American Physical Society.

• Received 18 December 1995

DOI:https://doi.org/10.1103/PhysRevA.54.2728