Complete elimination of information leakage in continuous-variable   quantum communication channels
  In all lossy communication channels realized to date, information is inevitably leaked to a potential eavesdropper. Here we present a communication protocol that does not allow for any information leakage to a potential eavesdropper in a purely lossy channel. By encoding information into a restricted Gaussian alphabet of squeezed states we show, both theoretically and experimentally, that the Holevo information between the eavesdropper and the intended recipient can be exactly zero in a purely lossy channel while minimized in a noisy channel. This result is of fundamental interest, but might also have practical implications in extending the distance of secure quantum key distribution. 
Christian S. Jacobsen and Lars S. Madsen and Vladyslav C. Usenko and   Radim Filip and Ulrik L. Andersen
quant-ph