Continuous variable quantum cryptography using coherent states

Frédéric Grosshans (1) , Philippe Grangier (1)

1 Laboratoire Charles Fabry de l'Institut d'Optique / Optique quantique

We propose several methods for quantum key distribution (QKD) based upon the generation and transmission of random distributions of coherent or squeezed states, and we show that they are are secure against individual eavesdropping attacks. These protocols require that the transmission of the optical line between Alice and Bob is larger than 50 %, but they do not rely on "non-classical" features such as squeezing. Their security is a direct consequence of the no-cloning theorem, that limits the signal to noise ratio of possible quantum measurements on the transmission line. Our approach can also be used for evaluating various QKD protocols using light with gaussian statistics.

Domaines: Physique Quantique [quant-ph]

Frédéric Grosshans, Philippe Grangier. Continuous variable quantum cryptography using coherent states. Physical Review Letters, 2002, 88, pp.057902. ⟨10.1103/PhysRevLett.88.057902⟩. ⟨hal-00509124⟩