The squashed entanglement of a quantum channel

Masahiro Takeoka, Saikat Guha, Mark M. Wilde

研究成果: Article査読

62 被引用数 (Scopus)

抄録

This paper defines the squashed entanglement of a quantum channel as the maximum squashed entanglement that can be registered by a sender and receiver at the input and output of a quantum channel, respectively. A new subadditivity inequality for the original squashed entanglement measure of Christandl and Winter leads to the conclusion that the squashed entanglement of a quantum channel is an additive function of a tensor product of any two quantum channels. More importantly, this new subadditivity inequality, along with prior results of Christandl and Winter, establishes the squashed entanglement of a quantum channel as an upper bound on the quantum communication capacity of any channel assisted by unlimited forward and backward classical communication. A similar proof establishes this quantity as an upper bound on the private capacity of a quantum channel assisted by unlimited forward and backward public classical communication. This latter result is relevant as a limitation on rates achievable in quantum key distribution. As an important application, we determine that these capacities can never exceed log((1+η)/(1-η)) for a pure-loss bosonic channel for which a fraction η of the input photons make it to the output on average. The best known lower bound on these capacities is equal to log(1/(1-η)). Thus, in the high-loss regime for which η ≪ 1, this new upper bound demonstrates that the protocols corresponding to the above lower bound are nearly optimal.

本文言語English
論文番号6832533
ページ(範囲)4987-4998
ページ数12
ジャーナルIEEE Transactions on Information Theory
60
8
DOI
出版ステータスPublished - 2014 8月
外部発表はい

ASJC Scopus subject areas

  • 情報システム
  • コンピュータ サイエンスの応用
  • 図書館情報学

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