Entanglement concentration for photon systems assisted with single photons

The entanglement concentration protocols (ECPs) are presented for concentrating arbitrary partially entangled Bell-like state, N-photon GHZ state and N-photon W state, respectively, and the corresponding maximally entangled state can be obtained finally with a certain probability. Besides, compared with other ECPs, the accurate coefficients of the initial partially entangled state in our ECPs do not need to know in advance. Moreover, current ECPs can be repeated to acquire a higher success probability. The devices used in the schemes are linear which leads to flexible operations and improves the performance greatly in the present experiment and our ECPs may be useful in the long-distance quantum information processing.