Two-photon four-qubit cluster state generation based on a polarization-entangled photon pair

We propose and experimentally demonstrate a two-photon four-qubit cluster state generator using linear optics and a single polarization-entangled photon-pair source based on spontaneous parametric down-conversion (SPDC). Our novel scheme provides greater design flexibility compared to previous schemes that rely on hyperentanglement. (c) 2007 Optical Society of America.