Learn 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.
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)
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)
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 allows two remote parties, Alice and Bob, to generate a secret key, with privacy guaranteed by quantum mechanics. It has been demonstrated in optical fibers by several groups [1,2,3]. However continuous active adjustment, either of polarization or path length in the setups was necessary. Our group introduced in 1997 an(More)
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)
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)
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)
It has been shown theoretically that a light amplifier working on the physical principle of stimulated emission should achieve optimal quantum cloning of the polarization state of light. We demonstrate close-to-optimal universal quantum cloning of polarization in a standard fiber amplifier for telecom wavelengths. For cloning 1-->2 we find a fidelity of(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)