Gregoire Ribordy

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We introduce a new class of quantum key distribution protocols, tailored to be robust against photon number splitting (PNS) attacks. We study one of these protocols, which differs from the original protocol by Bennett and Brassard (BB84) only in the classical sifting procedure. This protocol is provably better than BB84 against PNS attacks at zero error.
A secure communication network with quantum key distribution in a metropolitan area is reported. Six different QKD systems are integrated into a mesh-type network. GHz-clocked QKD links enable us to demonstrate the world-first secure TV conferencing over a distance of 45km. The network includes a commercial QKD product for long-term stable operation, and(More)
We investigate the performance of separate absorption multiplication InGaAs/InP avalanche photodiodes as single-photon detectors for 1.3- and 1.55-mum wavelengths. First we study afterpulses and choose experimental conditions to limit this effect. Then we compare the InGaAs/InP detector with a germanium avalanche photodiode; the former shows a lower(More)
We describe a new quantum key distribution (QKD) protocol that differs from the BB84 only in the classical sifting procedure: instead of revealing the basis, Alice reveals a pair of non-orthogonal states. The new protocol is as robust as BB84 against optimal individual eavesdropping, and is much more robust than BB84 against the most general photon-number(More)
Quantum Key Distribution (QKD), the most advanced technology of the field of quantum information, allows two remote parties to exchange a sequence of random bits and subsequently check their secrecy [1]. It has been extensively tested in the past couple of years over distances of a few tens of kilometers [2–6]. Its security relies on the fact that the bits(More)
General Trojan-horse attacks on quantum-key-distribution systems, i.e., attacks on Alice or Bob’s system via the quantum channel, are analyzed. We illustrate the power of such attacks with today’s technology and conclude that all systems must implement active counter measures. In particular, all systems must include an auxiliary detector that monitors any(More)
Document history: During the first year of the SECOQC project [1], Philippe Grangier initiated an internal debate regarding the " comparative advantages " of quantum key distribution (QKD). A first written contribution to this debate, by Philippe Grangier, Louis Salvail, Nicolas Gisin and Thierry Debuisschert [2], was then made available to all SECOQC(More)
An improved « plug & play » interferometric system for quantum key distribution is presented. Self-alignment and compensation of birefringence remain, while limitations due to reflections are overcome. Original electronics implementing the BB84 protocol makes adjustment simple. Key creation with 0.1 photon per pulse at a rate of 325 Hz with a 2.9% QBER –(More)
Some guidelines for the comparison of different quantum key distribution experiments are proposed. An improved « plug & play » interferometric system allowing fast key exchange is then introduced. Self-alignment and compensation of birefringence remain. Original electronics implementing the BB84 protocol and allowing user-friendly operation is presented.(More)
After a short introduction to classic cryptography we explain thoroughly how quantum cryptography works. We present then an elegant experimental realization based on a self-balanced interferometer with Faraday mirrors. This phase-coding setup needs no alignment of the interferometer nor polarization control, and therefore considerably facilitates the(More)