Quantum Channel Capacities with Passive Environment Assistance

Siddharth Karumanchi, Stefano Mancini, Andreas Winter, Dong Yang

Research output: Contribution to journalArticleResearchpeer-review

18 Citations (Scopus)


© 2016 IEEE. We initiate the study of passive environment-assisted communication via a quantum channel, modeled as a unitary interaction between the information carrying system and an environment. In this model, the environment is controlled by a benevolent helper, who can set its initial state such as to assist sender and receiver of the communication link (the case of a malicious environment, also known as jammer, or arbitrarily varying channel, is essentially well-understood and comprehensively reviewed). Here, after setting out precise definitions, focusing on the problem of quantum communication, we show that entanglement plays a crucial role in this problem: indeed, the environment-assisted capacity where the helper is restricted to product states between the channel uses is different from the one with unrestricted helper. Furthermore, prior shared entanglement between the helper and the receiver makes a difference, too.
Original languageEnglish
Article number7393566
Pages (from-to)1733-1747
JournalIEEE Transactions on Information Theory
Publication statusPublished - 1 Apr 2016


  • Quantum channels
  • entanglement
  • quantum capacity
  • superactivation


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