Multi-Photon Entanglement and Quantum Non-Locality

Abstract

We review recent experiments concerning multi-photon Greenberger-HorneZeilinger (GHZ) entanglement. We have experimentally demonstrated GHZ entanglement of up to four photons by making use of pulsed parametric downconversion. On the basis of measurements on three-photon entanglement, we have realized the first experimental test of quantum non-locality following from the GHZ argument. Not only does multi-particle entanglement enable various fundamental tests of quantum mechanics versus local realism, but it also plays a crucial role in many quantum-communication and quantumcomputation schemes.

Quantum imaging with N-photon states in position space

“…So far, up to six time-entangled photons have been produced through entanglement swapping [1] and photon triplets start being produced through cascaded nonlinear processes [2] or photon number post-selection in a single parametric process [3]. Multi-photon interferometry techniques have been developed to demonstrate the hyperentanglement of a large number of qubits [4] as well as phase super-sensitivity [5,6] (for a recent revue on N-photon entanglement and interferometry see [7]). Spatial entanglement [8] is particularly interesting for quantum information processing and communication because large Hilbert spaces can be easily manipulated using passive masks or active spatial light modulator [9][10][11][12][13][14].…”