Abstract

We put forward an efficient entanglement concentration protocol (ECP) for recovering the single-photon less-entangled $W$ state into the maximally entangled $W$ state with only two conventional auxiliary photons. The ECP includes two local steps, both of which are based on the weak cross-Kerr nonlinearities and the variable beam splitter (VBS). Benefiting from the cross-Kerr nonlinearities and the VBS, the ECP can be used repeatedly to further concentrate the less-entangled $W$ state. All the advantages indicate that our protocol may be feasible and convenient in current quantum communications areas.

© 2012 Optical Society of America

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