Random-party entanglement distillation in multiparty states

Abstract

We describe various results related to the random-party distillation of multiparty entangled states-that is, conversion of such states into entangled states shared between fewer parties, where those parties are not predetermined. In previous work we showed that certain output states (namely Einstein-Podolsky-Rosen pairs) could be reliably acquired from a prescribed initial multipartite state [namely the W state |W = 1 3 (| 100 + | 010 + | 001 )] via random-party distillation that could not be reliably created between predetermined parties. Here we provide a more rigorous definition of what constitutes "advantageous" random-party distillation. We show that random-party distillation is always advantageous for W-class three-qubit states (but only sometimes for Greenberger-Horne-Zeilinger class states). We show that the general class of multiparty states known as symmetric Dicke states can be readily converted to many other states in the class via random-party distillation. Finally we show that random-party distillation is provably not advantageous in the limit of multiple copies of pure states. © 2008 The American Physical Society.