Fundamental rate-loss tradeoff for optical quantum key distribution

Since 1984, various optical quantum key distribution (QKD) protocols have been proposed and examined. In all of them, the rate of secret key generation decays exponentially with distance. A natural and fundamental question is then whether there are yet-to-be discovered optical QKD protocols (without...

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Bibliographic Details
Published in:Nature communications, Vol. 5 (2014), p. 5235
Main Author: Takeoka, Masahiro (Author)
Other Involved Persons: Guha, Saikat ; Wilde, Mark M
Format: electronic Article
Language:English
ISSN:2041-1723
Item Description:Date Completed 06.04.2015
Date Revised 24.10.2014
published: Electronic
Citation Status PubMed-not-MEDLINE
Copyright: From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Physical Description:Online-Ressource
DOI:10.1038/ncomms6235
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  • Since 1984, various optical quantum key distribution (QKD) protocols have been proposed and examined. In all of them, the rate of secret key generation decays exponentially with distance. A natural and fundamental question is then whether there are yet-to-be discovered optical QKD protocols (without quantum repeaters) that could circumvent this rate-distance tradeoff. This paper provides a major step towards answering this question. Here we show that the secret key agreement capacity of a lossy and noisy optical channel assisted by unlimited two-way public classical communication is limited by an upper bound that is solely a function of the channel loss, regardless of how much optical power the protocol may use. Our result has major implications for understanding the secret key agreement capacity of optical channels-a long-standing open problem in optical quantum information theory-and strongly suggests a real need for quantum repeaters to perform QKD at high rates over long distances