Abstract: Quantum systems can share correlations which are stronger than those allowed by any classical (or local) theory. It is however unknown what limits the strength of quantum correlations. Information-causality (IC) has recently been proposed as the physical principle that would define quantum nonlocality. Indeed, this principle is always satisfied by quantum physics and succeed in ruling out many supra-quantum correlations (at least when only two systems are considered).
In this talk I will present a recent work where we investigate the behavior of IC in the multipartite scenario. We consider the simplest framework, where three distant parties establish correlations by measuring, each, two observables with two possible outcomes. We show that all, but one, nonlocal extremal correlations in this scenario violate information causality. This undetected correlation is shown to satisfy any bipartite physical principle.
Joint work with T. H. Yang, D. Cavalcanti, C. Teo and V. Scarani from CQT, Singapore. (available in arXiv:1108.2293)