Multiparticle entanglement and multiparticle protocols

by Mohamed Bourennane (SU Fysikum)

Thursday 29 May 2008, 10:00 → 11:00 Europe/Stockholm

Entanglement is one of the most puzzling features of quantum theory and of great importance for the new field of quantum information theory. The determination of whether a given state is entangled or not is one of the most challenging open problems. For multipartite entangled state Bell inequalities turned out not to be always suited to distinguish genuine multipartite entanglement from biseparable, triseparable, etc. entanglement. Only recently, significant progress in classifying multipartite entanglement has been achieved using entanglement witnesses. These observables can always be used to detect entanglement, when some apriory knowledge about the states under investigation is provided. It has been shown that witness operators can be implemented experimentally in a straightforward way by using local projective measurements, even for multipartite systems. We apply this scheme to experimentally detect entanglement of multiphoton states. These states are used for the realization of quantum multiparty communication protocols such as secret sharing, Byzantine agreement, liar detection, and tele-cloning.