9809010v1

related topics
{information, entropy, channel}
{states, state, optimal}
{vol, operators, histories}
{entanglement, phys, rev}
{state, phys, rev}
{error, code, errors}
{operator, operators, space}
{let, theorem, proof}
{key, protocol, security}
{observables, space, algebra}

On Quantum Fidelities and Channel Capacities

H. Barnum, E. Knill, M. A. Nielsen

abstract: We show the equivalence of two different notions of quantum channel capacity: that which uses the entanglement fidelity as its criterion of success in transmission, and that which uses the minimum fidelity of pure states in a subspace of the input Hilbert space as its criterion. As a corollary, any source with entropy rate less than the capacity may be transmitted with high entanglement fidelity. We also show that a restricted class of encodings is sufficient to transmit any quantum source which may be transmitted on a given channel. This enables us to simplify a known upper bound for the channel capacity. It also enables us to show that the availability of an auxiliary classical channel from encoder to decoder does not increase the quantum capacity.

oai_identifier:
oai:arXiv.org:quant-ph/9809010
categories:
quant-ph
comments:
13 pages, uses IEEEtran.cls, rawfonts.sty, somedefs.sty. Submitted to IEEE Transactions on Information Theory
arxiv_id:
quant-ph/9809010
journal_ref:
IEEE Trans.Info.Theor. 46 (2000) 1317-1329
created:
1998-09-04

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