Indirect Measurement for Optimal Quantum Communication Enhanced by Binary Non-standard Coherent States

It is well known that the Helstrom bound can be improved by generalizing the form of a coherent state. Thus, designing a quantum measurement achieving the improved Helstrom bound is important for novel quantum communication. In the present article, we analytically show that the improved Helstrom bound can be achieved by a projective measurement composed of orthogonal non-standard Schr\"{o}dinger cat states. Moreover, we numerically show that the improved Helstrom bound can be nearly achieved by an indirect measurement based on the Jaynes-Cummings model. As the Jaynes-Cummings model describes an interaction between a light and a two-level atom, we emphasize that the indirect measurement considered in this article has potential to be experimentally implemented.