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Passive Decoy-State Quantum Key Distribution with Coherent Light

Escuela de Ingeniería de Telecomunicación, Department of Signal Theory and Communications, University of Vigo, Campus Universitario, Vigo 36310, Pontevedra, Spain
ICFO-Institut de Ciències Fotòniques, Mediterranean Technology Park, Castelldefels 08860, Barcelona, Spain
ICREA-Institució Catalana de Recerca i Estudis Avanc¸ats, Barcelona 08010, Spain
Author to whom correspondence should be addressed.
Entropy 2015, 17(6), 4064-4082;
Received: 31 March 2015 / Revised: 26 May 2015 / Accepted: 9 June 2015 / Published: 12 June 2015
(This article belongs to the Special Issue Quantum Cryptography)
PDF [443 KB, uploaded 12 June 2015]


Signal state preparation in quantum key distribution schemes can be realized using either an active or a passive source. Passive sources might be valuable in some scenarios; for instance, in those experimental setups operating at high transmission rates, since no externally driven element is required. Typical passive transmitters involve parametric down-conversion. More recently, it has been shown that phase-randomized coherent pulses also allow passive generation of decoy states and Bennett–Brassard 1984 (BB84) polarization signals, though the combination of both setups in a single passive source is cumbersome. In this paper, we present a complete passive transmitter that prepares decoy-state BB84 signals using coherent light. Our method employs sum-frequency generation together with linear optical components and classical photodetectors. In the asymptotic limit of an infinite long experiment, the resulting secret key rate (per pulse) is comparable to the one delivered by an active decoy-state BB84 setup with an infinite number of decoy settings. View Full-Text
Keywords: quantum cryptography; quantum key distribution; quantum communication quantum cryptography; quantum key distribution; quantum communication
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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MDPI and ACS Style

Curty, M.; Jofre, M.; Pruneri, V.; Mitchell, M.W. Passive Decoy-State Quantum Key Distribution with Coherent Light. Entropy 2015, 17, 4064-4082.

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