Quantum key distribution with an efficient countermeasure against correlated intensity fluctuations in optical pulses

Ken Ichiro Yoshino, Mikio Fujiwara, Kensuke Nakata, Tatsuya Sumiya, Toshihiko Sasaki, Masahiro Takeoka, Masahide Sasaki, Akio Tajima, Masato Koashi, Akihisa Tomita

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

Quantum key distribution (QKD) allows two distant parties to share secret keys with the proven security even in the presence of an eavesdropper with unbounded computational power. Recently, GHz-clock decoy QKD systems have been realized by employing ultrafast optical communication devices. However, security loopholes of high-speed systems have not been fully explored yet. Here we point out a security loophole at the transmitter of the GHz-clock QKD, which is a common problem in high-speed QKD systems using practical band-width limited devices. We experimentally observe the inter-pulse intensity correlation and modulation pattern-dependent intensity deviation in a practical high-speed QKD system. Such correlation violates the assumption of most security theories. We also provide its countermeasure which does not require significant changes of hardware and can generate keys secure over 100 km fiber transmission. Our countermeasure is simple, effective and applicable to wide range of high-speed QKD systems, and thus paves the way to realize ultrafast and security-certified commercial QKD systems.

Original languageEnglish
Article number8
Journalnpj Quantum Information
Volume4
Issue number1
DOIs
Publication statusPublished - 2018 Dec 1
Externally publishedYes

ASJC Scopus subject areas

  • Computer Science (miscellaneous)
  • Statistical and Nonlinear Physics
  • Computer Networks and Communications
  • Computational Theory and Mathematics

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