Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues.
In this article, a fully integrated single photon detector including a silicon avalanche photodiode and a quenching circuit is presented. The low doping concentrations, inherent to the complementary metal–oxide–semiconductor ͑CMOS͒ high-voltage technology used, favor the absorption of red and infrared photons at the depletion region. The detection… (More)
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.
We present a fibre-optical quantum key distribution system. It works at 1550 nm and is based on the plug&play setup. We tested the stability under field conditions using aerial and terrestrial cables and performed a key exchange over 67 km between Geneva and Lausanne.
General Trojan horse attacks on quantum key distribution systems are analyzed. We illustrate the power of such attacks with today's technology and conclude that all system must implement active countermeasures. In particular all systems must include an auxiliary detector that monitors any incoming light. We show that such countermeasures can be efficient,… (More)
Quantum cryptography could be integrated in various existing concepts and protocols to secure Metropolitan Area Networks communications. One of the possible use of quantum cryptography is within IPSEC. The applications of quantum cryptography are linked to telecom-munication services that require very high level of security in Metropolitan Area Networks.… (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 present a full implementation of a quantum key distribution system using energy-time entangled photon pairs over a 30 km standard telecom fiber quantum channel. Two bases of two orthogonal states are implemented and the setup is shown to be robust to environmental constraints such as temperature variation. Two different ways to manage chromatic… (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)
We present a fibre-optical quantum key distribution system. It works at 1550nm and is based on the plug&play setup. We tested the stability under field conditions using aerial and terrestrial cables and performed a key exchange over 67 km between Geneva and Lausanne. Quantum cryptography or, more exactly, quantum key distribution (QKD) is the most advanced… (More)