Superactivation of bound entanglement

Phys Rev Lett. 2003 Mar 14;90(10):107901. doi: 10.1103/PhysRevLett.90.107901. Epub 2003 Mar 10.

Abstract

We show that, in a multiparty setting, two nondistillable (bound-entangled) states tensored together can make a distillable state. This is an example of true superadditivity of distillable entanglement. We also show that unlockable bound-entangled states cannot be asymptotically unentangled, providing the first proof that some states are truly bound-entangled in the sense of being both nondistillable and nonseparable asymptotically.