Entanglementassisted communication of classical and quantum information
Abstract
We consider the problem of transmitting classical and quantum information reliably over an entanglementassisted quantum channel. Our main result is a capacity theorem that gives a threedimensional achievable rate region. Points in the region are rate triples, consisting of the classical communication rate, the quantum communication rate, and the entanglement consumption rate of a particular coding scheme. The crucial protocol in achieving the boundary points of the capacity region is a protocol that we name the classicallyenhanced father protocol. The classicallyenhanced father protocol is more general than other protocols in the family tree of quantum Shannon theoretic protocols, in the sense that several previously known quantum protocols are now child protocols of it. The classicallyenhanced father protocol also shows an improvement over a timesharing strategy for the case of a qubit dephasing channelthis result justifies the need for simultaneous coding of classical and quantum information over an entanglementassisted quantum channel. Our capacity theorem is of a multiletter nature (requiring a limit over many uses of the channel), but it reduces to a singleletter characterization for at least three channels: the completely depolarizing channel, the quantum erasure channel, and the qubit dephasing channel.
 Publication:

arXiv eprints
 Pub Date:
 November 2008
 arXiv:
 arXiv:0811.4227
 Bibcode:
 2008arXiv0811.4227H
 Keywords:

 Quantum Physics;
 Computer Science  Information Theory
 EPrint:
 23 pages, 5 figures, 1 table, simplification of capacity regionit now has the simple interpretation as the unit resource capacity region translated along the classicallyenhanced father tradeoff curve