Multipartite positive-partial-transpose inequalities exponentially stronger than local reality inequalities

Abstract

We show that positivity of every partial transpose of N-partite quantum states implies inequalities on Bell correlations which are stronger than standard Bell inequalities by a factor of 2((N-1)/2). A violation of the inequality implies that the system is in a bipartite distillable entangled state. It turns out that a family of N-qubit bound entangled states proposed by Dur [Phys. Rev. Lett. 87, 230402 (2001)] violates the inequality for N >= 4.