Superactivation of Bound Entanglement
  We show that, in a multi-party setting, two non-distillable (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 non-distillable and non-separable asymptotically. 
Peter W. Shor, John A. Smolin and Ashish V. Thapliyal