16-QAM Quantum Receiver with Hybrid Structure Outperforming the Standard Quantum Limit

Abstract

Abstract. Quantum receivers which can discriminate phase shift keying (PSK) and pulse position modulation (PPM) signals below the standard quantum limit have been proposed and some have been demonstrated experimentally. But for quadrature amplitude modulation (QAM) signals, few literatures have been reported so far. It is important to reduce the average error probability of QAM signals below the standard quantum limit (SQL), since these modulation have a high spectral efficiency. In this paper, we present a quantum receiver for 16-QAM signals discrimination with hybrid structure, which contains a homodyne receiver and a displacement receiver. By numerical simulation, we prove that the performance of the quantum receiver can outperform the SQL, and it can be improved by an optimized displacement.

Quantum receiver for large alphabet communication

“…There have been quite a few theoretical studies of quantum receivers for binary and larger alphabets. The protocols studied are pulse amplitude modulation, (a) where the information is encoded as the amplitude of a carrier wave [27], phase shift keying (PSK), where the information is encoded in phase [28,29], and quadrature amplitude modulation (QAM), where a combination of amplitude and phase is used for encoding [30]. To date, quantum receivers that discriminate as many as 4 coherent states with error rates below the SQL have been experimentally demonstrated [31,32].…”