title: Catalysis in nonlocal quantum operations.
abstract: We show how entanglement can be used, without being consumed, to accomplish unitary operations that could not be performed without it. When applied to infinitesimal transformations, our method makes equivalent, in the sense of Hamiltonian simulation, a whole class of otherwise inequivalent two-qubit interactions. The new catalysis effect also implies the asymptotic equivalence of all such interactions.
authors.affiliation: Institut für Theoretische Physik, Universität Innsbruck, A-6020 Innsbruck, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Vidal
authors.forename: J I
authors.initials: JI
authors.lastname: Cirac