Entanglement-assisted local transformations between inequivalent classes of three-particle entangled states

We show that bipartite and tripartite entangled states cannot be used as catalysis states to enable local transformations inbetween inequivalent classes of three-particle entangled states which are non-interchangeable under local transformations. We find the optimal protocol for conversion of a certain family of the W-states and an EPR-pair into the GHZ-state. (C) 2001 Elsevier Science B.V. All fights reserved.