Multiphoton entanglement: production and applications

Some new experiments leading to observation of multi-photon entanglement will be presented. They utilize multi-pair emissions in a down-conversion crystal. In configurations that avoid interferometric overlaps this leads to a high visibility multi-photon interference. General theoretical results concerning the influence of photon statistics and distinguishability on the interference effects in such experiments is be given. Methods of detection of entanglement in multi-qubit systems, via Bell's theorem and a non-linear generalization of entanglement witnesses, will be presented. Finally it will be shown that multi-photon entanglement can be applied to reduce of communication complexity of some computational tasks.