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Bell inequalities and distillability in N-quantum-bit systems

Antonio Acin, Valerio Scarani, Michael M. Wolf

Phys. Rev. A 66, 042323 **, (2002)

DOI: 10.1103/PhysRevA.66.042323 Pfeil
**: quant-ph/0206084 Pfeil

Abstract: The 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.