Nonadditivity of bipartite distillable entanglement follows from a conjecture on bound entangled Werner states

An even stronger effect that bound entangled states can have is presented; states which are conjectured to be undistillable become distillable by adding positive partial transpose (PPT) bound entanglement. These conjectured bound entangled states are referred to as negative partial transpose (NPT) bound entangled states.