One-step distillation of local-unitary-equivalent GHZ-type states

Abstract

Entanglement distillation plays a very important role in quantum information science. Distillation of high-purity Greenberger–Horne–Zeilinger (GHZ) states has been widely studied. We here show that a pure GHZ-type entangled state or its local unitary (LU)-equivalent state could be extracted from two copies of a particular multipartite mixed state (e.g., an X state) in a single step. Such one-step distillation schemes for LU-equivalent states are expected to shed light on mixed-state manipulation and purification, as well as establish a link between entanglement classification and distillation.