Four-photon interference: a realizable experiment to demonstrate violationof EPR postulates for perfect correlations

Bell's theorem reveals contradictions between the predictions of quantum me chanics and the EPR postulates for a pair of particles only in situations i nvolving imperfect statistical correlations. However, with three or more pa rticles, contradictions emerge even for perfect correlations. We describe a n experiment which can be realized in the laboratory, using four-photon ent angled states generated by parametric down-conversion, to demonstrate this contradiction at the level of perfect correlations.