title: Capacities of lossy bosonic memory channels.
abstract: We introduce a general model describing correlated noise effects in quantum optical communication via attenuating media. The memory effects account for the environment finite relaxation times, which are unavoidable in any realistic model. The use of a proper set of collective field variables allows us to unravel the memory, showing that the n-fold concatenation of the memory channel is unitarily equivalent to the direct product of n single-mode lossy bosonic channels. We then compute the ultimate (classical and quantum) transmission rates, showing their enhancement with respect to the memoryless case and proving that coherent state encoding is optimal.
authors.affiliation: Dipartimento di Fisica, Università di Camerino, via Madonna delle Carceri 9, I-62032 Camerino, Italy.
authors.forename: Cosmo
authors.initials: C
authors.lastname: Lupo
authors.forename: Vittorio
authors.initials: V
authors.lastname: Giovannetti
authors.forename: Stefano
authors.initials: S
authors.lastname: Mancini