ENTANGLEMENT AND PHOTONS

Novel methods of producing and analyzing entangled states of photons a re presented. E.g., using multiport beam splitters, it will be possibl e to study Einstein-Podolsky-Rosen correlations in higher dimensional Hilbert space. As an explicit example, we present the design and theor y of a multiport beam splitter with three input ports and three output ports, such that any amplitude incident at one input port is distribu ted equally over the output ports. Results for a two-photon, two-tritt er Bell experiment, where novel EPR correlations occur, will be presen ted. General conditions are presented for an optical experiment involv ing independent sources that are a valid test of local realism. Using independent sources, one can realize an ''event-ready'' Bell-EPR exper iment in which one can measure directly the probabilities of the vario us outcomes including nondetection of both particles. The proposal inv olves two parametric down-converters. Subcoherence-time monitoring of the idlers provides a noninteractive quantum measurement entangling an d preselecting the independent signals without touching them. The cond itions for high fringe visibility and particle collection efficiency a s required for a Bell test are given. A proposal for a GHZ test is pre sented.