Quantum direct communication with continuous variables

¹  MIT - Research Laboratory of Electronics - Cambridge MA 02139, USA
²  Computer Science, University of York - YO10 5DD York, UK, EU
³  CNISM and Dipartimento di Fisica, Università di Camerino - I-62032 Camerino, Italy, EU
⁴  MIT - Department of Mechanical Engineering - Cambridge MA 02139, USA

Corresponding author: pirs@mit.edu

Received: 5 February 2008
Accepted: 12 September 2008

Abstract

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.