Activating bound entanglement in multi-particle systems

We analyze the existence of activable bound entangled states inmulti-particle systems. We first give a series of examples which illustratesome different ways in which bound entangled states can be activated by lettingsome of the parties to share maximally entangled states. Then, we derivenecessary conditions for a state to be distillable as well as to be activable.These conditions turn out to be also sufficient for a certain family ofmulti-qubit states. We use these results to explicitely to construct statesdisplaying novel properties related to bound entanglement and its activation