Quantum capacity can be greater than private information for arbitrarily many uses

D. Elkouss, Sergii Strelchuk

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

Abstract

The quantum capacity of a quantum channel is always smaller than the capacity of the channel for private communication. However, both quantities are given by the infinite regularization of respectively the coherent and the private information. Here, we construct a family of channels for which the private and coherent information can remain strictly superadditive for unbounded number of uses. We prove this by showing that the coherent information is strictly larger than the private information of a smaller number of uses of the channel. It turns out that even though the quantum capacity is upper bounded by the private capacity, the non-regularized quantities can be interleaved. From an operational point of view, the private capacity can be used for gauging the practical value of quantum channels for secure communication and, consequently, for key distribution. We thus show that in order to evaluate the interest a channel for this task it is necessary to optimize the private information over an unlimited number of uses of the channel.

Original languageEnglish
Title of host publication10th Conference on the Theory of Quantum Computation, Communication and Cryptography, TQC 2015
PublisherSchloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
Pages64-72
Number of pages9
Volume44
ISBN (Electronic)9783939897965
DOIs
Publication statusPublished - 1 Nov 2015
Event10th Conference on the Theory of Quantum Computation, Communication and Cryptography, TQC 2015 - Brussels, Belgium
Duration: 20 May 201522 May 2015

Conference

Conference10th Conference on the Theory of Quantum Computation, Communication and Cryptography, TQC 2015
CountryBelgium
CityBrussels
Period20/05/1522/05/15

Keywords

  • Capacity
  • Private information
  • Quantum channels

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