Quantum correlation between photons separated by more than 10 km

Summary form only given.In this presentation experimental results of a two-photon interference experiment will be presented and discussed. The two photons, produced by parametric downconversion in a KNbO/sub 3/ crystal, were analyzed with two interferometers physically separated by more than 10 km with the source roughly at the center. The results clearly indicate that the famous spooky action at a distance extends over very large distances. Indeed, from the measured two-photon fringe visibility of 81.6% we infer a violation of the Bell inequality by 10 standard deviations.