Efficient entanglement concentration for arbitrary less-hyperentanglement multi-photon W states with linear optics

We present an efficient protocol to concentrate arbitrary less-hyperentangled multi-photon W states to the maximally hyperentangled multi-photon W state with parameter-splitting method and linear optics elements. Compared with previous entanglement concentration works, the present protocol does not need two copies of partially entangled states or the ancillary single photon. Moreover, we discuss the feasibility of the setups of the protocol, concluding that the present protocol is feasible with the current technology. Thus, the protocol may be more meaningful in practical quantum information applications.