Document Type
Article
Publication Date
10-24-2014
Abstract
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.
Publication Source (Journal or Book title)
Nature Communications
Recommended Citation
Takeoka, M., Guha, S., & Wilde, M. (2014). Fundamental rate-loss tradeoff for optical quantum key distribution. Nature Communications, 5 https://doi.org/10.1038/ncomms6235