Activating bound entanglement in multiparticle systems - art. no. 022302

We analyze the existence of activable bound entangled states in multipartic le systems. We first give a series of examples that illustrate some differe nt ways in which bound entangled states can be activated by letting some of the parties share maximally entangled states. Then, we derive necessary co nditions for a state to be distillable as well as to be activable. These co nditions turn out to be also sufficient for a certain family of multiqubit states. We use these results to explicitely construct states displaying pro perties related to bound entanglement and its activation.