Linear optical generation of multipartite entanglement with conventional photon detectors

A simple experimental scheme is proposed to generate a three-photon entangled W state and a genuine four-photon entangled state parallel to chi(00)> that has many interesting entanglement properties and possible applications in quantum information processing. These multipartite entangled states can be generated with a certain success probability. We show that even when the quantum efficiency of the detector is eta=0.75, the success probability can reach 2.8x10(-3) for W-state production and 3.0x10(-9) for parallel to chi(00)>-state production. The scheme is based only on simple linear optical elements and conventional photon detectors, which greatly decrease the experimental difficulty of implementing linear optical quantum computation.