Archive ouverte UNIGE | last documents for author 'Michael Wolf'https://archive-ouverte.unige.ch/Latest objects deposited in the Archive ouverte UNIGE for author 'Michael Wolf'engViolation of Bell s inequalities and distillability for N qubitshttps://archive-ouverte.unige.ch/unige:47353https://archive-ouverte.unige.ch/unige:47353We consider quantum systems composed of N qubits, and the family of all Bell's correlation inequalities for two two-valued measurements per site. We show that if an N-qubit state ρ violates any of these inequalities, then it is at least bipartite distillable. Indeed there exists a link between the amount of Bell's inequality violation and the degree of distillability. Thus, we strengthen the interpretation of Bell's inequalities as detectors of useful entanglement.Fri, 27 Feb 2015 14:36:21 +0100Bell's inequalities and distillability in N-quantum-bit systemshttps://archive-ouverte.unige.ch/unige:47351https://archive-ouverte.unige.ch/unige:47351The relation between Bell inequalities with two two-outcome measurements per site and distillability is analyzed in systems of an arbitrary number of quantum bits. We observe that the violation of any of these inequalities by a quantum state implies that pure-state entanglement can be distilled from it. The corresponding distillation protocol may require that some of the parties join into several groups. We show that there exists a link between the amount of the Bell inequality violation and the size of the groups they have to form for distillation. Thus, a strong violation is always sufficient for full N-partite distillability. This result also allows for a security proof of multi-partite quantum key distribution (QKD) protocols.Fri, 27 Feb 2015 14:35:27 +0100