title: Imprinting complete information about a quantum channel on its output state.
abstract: We introduce a novel property of bipartite quantum states, which we call faithfulness, and we say that a state is faithful when acting with a channel on one of the two quantum systems; the output state carries complete information about the channel. The concept of faithfulness can also be extended to sets of states, when the output states altogether carry a complete imprinting of the channel. Measures of degrees of faithfulness are proposed.
authors.affiliation: Quantum Optics and Information Group, Istituto Nazionale di Fisica della Materia, Unità di Pavia and Dipartimento di Fisica A. Volta, via Bassi 6, I-27100 Pavia, Italy. dariano@unipv.it
authors.forename: Giacomo Mauro
authors.initials: GM
authors.lastname: D'Ariano
authors.forename: Paoloplacido
authors.initials: P
authors.lastname: Lo Presti