Scheme for linear optical preparation of a type of four-photon entangled state with conventional photon detectors

We propose a simple experimental scheme to prepare a type of four-photon entangled state |chi > that has many interesting entanglement properties and possible applications in quantum information processing with a certain success probability. The proposed setup involves only simple linear optical devices, a single-photon polarization state, three pairs of two-photon polarization entangled states, and the conventional photon detectors that cannot distinguish a single photon from two or more photons, which greatly simplify the experimental realization of the scheme.