Optimized decision strategy for quadrature phase-shift-keying unambiguous states discrimination

Quantum-enhanced measurement can unambiguously discriminate coherent states with accuracy beyond what is fundamentally possible with conventional technologies. However, this advantage can be achieved only if quantum-enhanced measurement technologies are robust against to real-world imperfections. Improving resistance to real-world imperfections such as imperfect interference and dark count rate to enhance performance is of particular importance for an unambiguous state discrimination scenario. In this paper, we demonstrate an optimized decision strategy for quadrature phase-shift-keying unambiguous states discrimination, which to make the correct probability close to optimal. In addition, the error probability of the scheme is lower than ideal heterodyne measurement scheme when the average photon number of the signal is less than 4.5. The optimized decision strategy is based on the probability of photon-detection in measurement. Our demonstration shows that optimized decision strategy can provide practical advantages over conventional technologies for coherent optical communication.