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Evaluation of the phase randomness of a light source in quantum-key-distribution systems with an attenuated laser

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Please use this identifier to cite or link to this item:http://hdl.handle.net/2115/57548

Title: Evaluation of the phase randomness of a light source in quantum-key-distribution systems with an attenuated laser
Authors: Kobayashi, Toshiya Browse this author
Tomita, Akihisa Browse this author →KAKEN DB
Okamoto, Atsushi Browse this author →KAKEN DB
Issue Date: 18-Sep-2014
Publisher: American Physical Society
Journal Title: Physical Review A
Volume: 90
Issue: 3
Start Page: 32320
Publisher DOI: 10.1103/PhysRevA.90.032320
Abstract: Phase-randomized light is one of the key assumptions in the security proof of the Bennett-Brassard 1984 (BB84) quantum-key-distribution (QKD) protocol using an attenuated laser. Though the assumption has been believed to be satisfied for conventional systems, it should be reexamined for current high-speed QKD systems. The phase correlation may be induced by the overlap of the optical pulses, the interval of which decreases as the clock frequency increases. The phase randomness was investigated experimentally by measuring the visibility of interference. An asymmetric Mach-Zehnder interferometer was used to observe the interference between adjacent pulses from a gain-switched distributed feedback laser diode driven at 10 GHz. Low visibility was observed when the minimum drive current was set far below the threshold, while interference emerged when the minimum drive current was close to the threshold. The theoretical evaluation on the impact of the imperfect phase randomization provides target values for the visibility to guarantee the phase randomness. The experimental and theoretical results show that secure implementation of decoy BB84 protocol is achievable even for the 10-GHz clock frequency by using the laser diode under proper operating conditions.
Rights: ©2014 American Physical Society
Type: article
URI: http://hdl.handle.net/2115/57548
Appears in Collections:情報科学院・情報科学研究院 (Graduate School of Information Science and Technology / Faculty of Information Science and Technology) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 富田 章久

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