License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.TQC.2014.48
URN: urn:nbn:de:0030-drops-48054
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2014/4805/
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Cubitt, Toby ; Mancinska, Laura ; Roberson, David ; Severini, Simone ; Stahlke, Dan ; Winter, Andreas

Bounds on Entanglement Assisted Source-channel Coding Via the Lovász Theta Number and Its Variants

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Abstract

We study zero-error entanglement assisted source-channel coding (communication in the presence of side information). Adapting a technique of Beigi, we show that such coding requires existence of a set of vectors satisfying orthogonality conditions related to suitably defined graphs G and H. Such vectors exist if and only if theta(G) <= theta(H) where theta represents the Lovász number. We also obtain similar inequalities for the related Schrijver theta^- and Szegedy theta^+ numbers.

These inequalities reproduce several known bounds and also lead to new results. We provide a lower bound on the entanglement assisted cost rate. We show that the entanglement assisted independence number is bounded by the Schrijver number: alpha^*(G) <= theta^-(G). Therefore, we are able to disprove the conjecture that the one-shot entanglement-assisted zero-error capacity is equal to the integer part of the Lovász number. Beigi introduced a quantity beta as an upper bound on alpha^* and posed the question of whether beta(G) = \lfloor theta(G) \rfloor. We answer this in the affirmative and show that a related quantity is equal to \lceil theta(G) \rceil. We show that a quantity chi_{vect}(G) recently introduced in the context of Tsirelson's conjecture is equal to \lceil theta^+(G) \rceil.

BibTeX - Entry

@InProceedings{cubitt_et_al:LIPIcs:2014:4805,
  author =	{Toby Cubitt and Laura Mancinska and David Roberson and Simone Severini and Dan Stahlke and Andreas Winter},
  title =	{{Bounds on Entanglement Assisted Source-channel Coding Via the Lov{\'a}sz Theta Number and Its Variants}},
  booktitle =	{9th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2014)},
  pages =	{48--51},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-73-6},
  ISSN =	{1868-8969},
  year =	{2014},
  volume =	{27},
  editor =	{Steven T. Flammia and Aram W. Harrow},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{http://drops.dagstuhl.de/opus/volltexte/2014/4805},
  URN =		{urn:nbn:de:0030-drops-48054},
  doi =		{10.4230/LIPIcs.TQC.2014.48},
  annote =	{Keywords: source-channel coding, zero-error capacity, Lov{\'a}sz theta}
}

Keywords: source-channel coding, zero-error capacity, Lovász theta
Collection: 9th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2014)
Issue Date: 2014
Date of publication: 11.12.2014

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