Violations of local realism in multiphoton interference experiments

Spontaneous parametric down-conversion is a convenient source of pairs of entangled photons. Within special interferometric configurations involving either two sources of this kind or double emissions from such a source, one can oh serve three-photon Greenberger-Horne-Zeilenger-type interference effects. Unfortunately, events of some other types necessarily occur. It is shown that under specific operational conditions, thus far not met by the experiments, the entirety of the phenomena observed in such experiments has no local realistic model. However, one can show this only by analyzing the entire pattern of all events predicted by quantum mechanics.