Berlin 2014 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 64: Quantum information: Concepts and methods V

Q 64.1: Talk

Friday, March 21, 2014, 14:00–14:15, Kinosaal

Experimental test of a four-party GHZ-theorem — •Marie-Christine Röhsner, Chiara Greganti, Stefanie Barz, and Philip Walther — Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria

Nonlocality - the fact that quantum mechanical objects can exhibit correlations that cannot be explained by assigning local hidden variables to each object - plays a major role in quantum information science. Whereas two-party nonlocality has already been thoroughly investigated in the last decades of research, the multiparticle case is a more complex subject and still holds some open questions. The Greenberger-Horne-Zeilinger (GHZ) theorem allows us to experimentally test the predictions of quantum mechanics against those of local hidden variable theories using multiparticle states. Here we present an experimental test of a GHZ-theorem for 4-qubit states using an irreducible set of mutually commuting observables. We use sets of measurements in which every single-qubit observable appears an even number of times. Therefore the overall product of the measurement outcomes will always be +1 in any local hidden variable theory. On the contrary quantum mechanics predicts an outcome of -1. [1] The experiment is realized by using an entangled 4-qubit photonic cluster state. We measure five different 4-qubit-observables which allows us to demonstrate genuine 4-party irreducible nonlocality.

[1] M. Waegell, arXiv:1307.6264 [quant-ph].