Direct measurement of the concurrence of hybrid entangled state based on parity check measurements**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474168 and 11747161) and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China.

Abstract

The hybrid entangled state is widely discussed in quantum information processing. In this paper, we propose the first protocol to directly measure the concurrence of the hybrid entangled state. To complete the measurement, we design parity check measurements (PCMs) for both the single polarization qubit and the coherent state. In this protocol, we perform three rounds of PCMs. The results show that we can convert the concurrence into the success probability of picking up the correct states from the initial entangled states. This protocol only uses polarization beam splitters, beam splitters, and weak cross-Kerr nonlinearities, which is feasible for future experiments. This protocol may be useful in future quantum information processing.