Experimental demonstration of long-distance continuous-variable quantum key distribution

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P. Jouguet, S. Kunz-Jaques, A. Leverrier, Ph. Grangier and E. Diamanti
Nature Photonics 7, 378-381 (2013)

Continuous-variable systems represent a valid alternative to QKD systems based on finite-dimensional
encodings. Their major advantage is that they only require standard telecommunication technology, and in
particular, that they do not use photon counters. However, these systems were considered up till now
unsuitable for long-distance communication.

In their work, Jouguet and colleagues overcome all previous limitations and demonstrate for the first time
continuous-variable quantum key distribution over 80 km of optical fibre. The demonstration includes all
aspects of a practical scenario, with real-time generation of secret keys, stable operation in a regular
environment, and use of finite-size data blocks for secret information computation and key distillation.