title: Entanglement cost of bipartite mixed states.
abstract: We compute the entanglement cost of several families of bipartite mixed states, including arbitrary mixtures of two Bell states. This is achieved by developing a technique that allows us to ascertain the additivity of the entanglement of formation for any state supported on specific subspaces. As a side result, the proof of the irreversibility in asymptotic local manipulations of entanglement is extended to two-qubit systems.
authors.affiliation: Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: G
authors.initials: G
authors.lastname: Vidal
authors.forename: W
authors.initials: W
authors.lastname: Dür
authors.forename: J I
authors.initials: JI
authors.lastname: Cirac