Implementation of continuous variable quantum cryptography in optical   fibres using a go-&-return configuration
  We demonstrate an implementation of quantum key distribution with continuous variables based on a go-&-return configuration over distances up to 14km. This configuration leads to self-compensation of polarisation and phase fluctuations. We observe a high degree of stability of our set-up over many hours. 
Matthieu Legre, Hugo Zbinden, Nicolas Gisin