Multi-photon Entanglement Concentration Protocol for Partially Entangled W States with Projection Measurement

Abstract

We propose a novel entanglement concentration protocol (ECP) for nonlocal N-photon systems in a partially entangled pure W-class state, following some ideas in the work by Deng (Phys. Rev. A 85:022311, 2012). Our ECP resorts to an ancillary single photon and the projection measurement on it. Compared with other ECPs for W-class states, our ECP requires only one copy of the multipartite entangled system in a partially entangled W-class pure state, not two copies, which reduces the difficulty of its implementation largely. Moreover, it requires only one of the N parties in quantum communication to perform the local unitary operation for reconstructing the standard W state from the W-class state and it only resorts to linear optical elements for its implementation. All these advantages make our ECP more feasible than others in practical applications in quantum communication.