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Published July 2008 | Published
Journal Article Open

Capacity Theorems for Quantum Multiple-Access Channels: Classical-Quantum and Quantum-Quantum Capacity Regions

Abstract

In this paper, we consider quantum channels with two senders and one receiver. For an arbitrary such channel, we give multiletter characterizations of two different two-dimensional capacity regions. The first region comprises the rates at which it is possible for one sender to send classical information, while the other sends quantum information. The second region consists of the rates at which each sender can send quantum information. For each region, we give an example of a channel for which the corresponding region has a single-letter description. One of our examples relies on a new result proved here, perhaps of independent interest, stating that the coherent information over any degradable channel is concave in the input density operator. We conclude with connections to other work and a discussion on generalizations where each user simultaneously sends classical and quantum information.

Additional Information

© Copyright 2008 IEEE. Reprinted with permission. Manuscript received August 4, 2005; revised October 15, 2007. [Date Published in Issue: 2008-06-17] The work of J. Yard was supported by the Army Research Office MURI under Contract DAAD-19-99-1-0215, by the National Science Foundation under Grant CCR-0311633, by the Stanford Networking Research Center under Grant 1059371-6-WAYTE, by CIFAR through McGill University, by the National Science Foundation (NSF) under Grant PHY-0456720 through Caltech, and by the Center for Nonlinear Studies (CNLS), the Quantum Institute, and the LDRD program of the U.S. Department of Energy through LANL. The work of P. Hayden was supported by CIFAR, by the Sherman Fairchild Foundation, and by the U.S. National Science Foundation under Grant EIA-0086038. Most of this research was done when J. Yard was with the Information Systems Laboratory, Stanford University, Stanford, CA. J. Yard would like to thank T. Cover for much useful input and feedback at many stages during the process of writing of this manuscript, and Y.H. Kim for useful discussions regarding classical multiple-access channels. Communicated by A. Winter, Associate Editor for Quantum Information Theory. Color version of Figure 1 in this paper is available online at http://ieeexplore.ieee.org.

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