Fusion of W-like states in optical system

An effective scheme is proposed for preparing large-scale maximally entangled W states by fusing arbitrary-size polarization entangled W or W-like states via polarization-dependent beam splitter (PDBS). In our scheme, Wm+n-1 state can be generated from an n-qubit W state and an m-qubit W state, and Wm+n+t-2 state can be generated from W-m, W-n and W-t states. The fusion process can start with Bell states too. Because PDBS has selective transmission rates for different polarization states, our fusion has a distinct property, i.e. a large-scale maximally entangled W state can he generated by fusing small-size W-like states, and the cost analyses indicate that our fusion scheme is more efficient than the previous one in fusing W-like states. In addition, there is no need for any controlled quantum gate and any ancillary photon in our scheme, so it is simple and feasible.