title: Direct and reverse secret-key capacities of a quantum channel.
abstract: We define the direct and reverse secret-key capacities of a memoryless quantum channel as the optimal rates that entanglement-based quantum-key-distribution protocols can reach by using a single forward classical communication (direct reconciliation) or a single feedback classical communication (reverse reconciliation). In particular, the reverse secret-key capacity can be positive for antidegradable channels, where no forward strategy is known to be secure. This property is explicitly shown in the continuous variable framework by considering arbitrary one-mode Gaussian channels.
authors.affiliation: MIT-Research Laboratory of Electronics, Cambridge, Massachusetts 02139, USA.
authors.forename: Stefano
authors.initials: S
authors.lastname: Pirandola
authors.forename: Raul
authors.initials: R
authors.lastname: García-Patrón
authors.forename: Samuel L
authors.initials: SL
authors.lastname: Braunstein
authors.forename: Seth
authors.initials: S
authors.lastname: Lloyd