Polarization-entangled W state using parametric down-conversion -: art. no. 064301

An experimental scheme for preparing a polarization entangled W states from four photons emitted by parametric down-conversion is,proposed. We consider two different configurations and a method of improving, the yield by using single-photon sources. In the proposed scheme, one uses only linear optical elements and, photon detectors, so that this scheme is feasible by current technologies.