All previous tests of local realism have studied correlations between single-particle measurements. In the present experiment, we have performed a Bell experiment on three particles in which one of the measurements corresponds to a projection onto a maximally-entangled state. We show theoretically and experimentally, that correlations between these entangled measurements and single-particle measurements are too strong for any local-realistic theory and are experimentally exploited to violate a CHSH-Bell inequality by more than 5 standard deviations. We refer to this possibility as "entangled entanglement".
@article{arxiv.quant-ph/0508183,
title = {Experimental Entangled Entanglement},
author = {Philip Walther and Kevin J. Resch and Caslav Brukner and Anton Zeilinger},
journal= {arXiv preprint arXiv:quant-ph/0508183},
year = {2009}
}