We show how continuous variable systems can allow the direct communication of messages with an acceptable degree of privacy. This is possible by combining a suitable phase-space encoding of the plain message with real-time checks of the quantum communication channel. The resulting protocol works properly when a small amount of noise affects the quantum channel. If this noise is non-tolerable, the protocol stops leaving a limited amount of information to a potential eavesdropper.
@article{arxiv.0802.0656,
title = {Quantum Direct Communication with Continuous Variables},
author = {Stefano Pirandola and Samuel L. Braunstein and Stefano Mancini and Seth Lloyd},
journal= {arXiv preprint arXiv:0802.0656},
year = {2008}
}