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Quantum Capacities of Channels with small Environment

Michael M. Wolf, David Perez-Garcia

Phys. Rev. Lett. 98, 130501 **, (2007)

DOI: 10.1103/PhysRevLett.98.130501 Pfeil
**: quant-ph/0606132 Pfeil

Abstract: We investigate the capacity of bosonic quantum channels for the transmission of quantum information. Achievable rates are determined from measurable moments of the channel by showing that every channel can asymptotically simulate a Gaussian channel which is characterized by second moments of the initial channel. We calculate the quantum capacity for a class of Gaussian channels, including channels describing optical fibers with photon losses, by proving that Gaussian encodings are optimal. Along the way we provide a complete characterization of degradable Gaussian channels and those arising from teleportation protocols.