Optimal multi-photon entanglement concentration with the photonic Faraday rotation**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474168 and 61401222), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20151502), the Qing Lan Project of Jiangsu Province, China, and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Abstract

We put forward an optimal entanglement concentration protocol (ECP) for recovering an arbitrary less-entangled multi-photon Greenberger–Horne–Zeilinger (GHZ) state into the maximally entangled GHZ state based on the photonic Faraday rotation in low-quality (Q) cavity. In the ECP, only one pair of less-entangled multi-photon GHZ state and one auxiliary photon are required, and the concentration task can be realized by local operations. Moreover, our ECP can be used repeatedly to further concentrate the discarded items of conventional ECPs, which can increase its success probability largely. Under the practical imperfect detection condition, our protocol can still work with relatively high success probability. This ECP has application potential in current and future quantum communication.