Qubit Channels Which Require Four Inputs to Achieve Capacity: Implications for Additivity Conjectures
量子物理
2007-05-23 v2
摘要
An example is given of a qubit quantum channel which requires four inputs to maximize the Holevo capacity. The example is one of a family of channels which are related to 3-state channels. The capacity of the product channel is studied and numerical evidence presented which strongly suggests additivity. The numerical evidence also supports a conjecture about the concavity of output entropy as a function of entanglement parameters. However, an example is presented which shows that for some channels this conjecture does not hold for all input states. A numerical algorithm for finding the capacity and optimal inputs is presented and its relation to a relative entropy optimization discussed.
引用
@article{arxiv.quant-ph/0403176,
title = {Qubit Channels Which Require Four Inputs to Achieve Capacity: Implications for Additivity Conjectures},
author = {Masahito Hayashi and Hiroshi Imai and Keiji Matsumoto and Mary Beth Ruskai and Toshiyuki Shimono},
journal= {arXiv preprint arXiv:quant-ph/0403176},
year = {2007}
}
备注
19 pages, 15 figures. several typos corrected in v2