Enhanced optimal quantum communication by a generalized phase-shift-keying coherent signal

Abstract

It is well known that the maximal success probability of the binary quantum communication can be improved by using a sub-Poissonian nonstandard coherent state as an information carrier. In the present article, we consider the quantum communication with $N$-ary phase-shift-keying ($N$-PSK) signal for an arbitrary positive integer $N>1$. By using nonstandard coherent state, we analytically provide the maximal success probability of the quantum communication with $N$-PSK. Unlike the binary case, there is a case that the guessing probability of $N$-PSK quantum communication can be improved by some non-sub-Poissonian, nonstandard coherent state.