Hardy's nonlocality for generalized n-particle GHZ states

In this Letter we extend Hardy's nonlocality proof for two spin-1/2 particles [Phys. Rev. Lett. 71 (1993) 1665] to the case of n spin-1/2 particles configured in the generalized GHZ state. We show that, for all n greater than or equal to 3, any entangled GHZ state violates the Bell inequality associated with the Hardy experiment. This feature is important since it has been shown [Phys. Rev. Lett. 88 (2002) 210402] that, for all n odd, there are entangled GHZ states that do not violate any standard n-particle correlation Bell inequality. (C) 2004 Elsevier B.V. All rights reserved.