Irreversibility for all bound entangled states

Abstract

We derive a new inequality for entanglement for a mixed four-partite state. Employing this inequality, we present a one-shot lower bound for entanglement cost and prove that entanglement cost is strictly larger than zero for any entangled state. We demonstrate that irreversibility occurs in the process of formation for all non-distillable entangled states. In this way we solve a long standing problem, of how "real" is entanglement of bound entangled states. Using the new inequality we also prove impossibility of local-cloning of a known entangled state.

The publication version. As noted in quant-ph/0510035, the result also implies that the mathematical definition of entangled states is equivalent to the physical definition in the sense of states preparation by LOCC