Abstract

Communication protocols based on quantum states of light have attracted increasing interest in the recent years, since they offer the possibility of enhancing either the communication capacity or the security by exploiting the very quantum nature of the information carriers. While first theoretical ideas and practical realizations started from discrete variables (DC) coding (practically based on the weak laser beams and SPDC-generated photon pairs), the continuous variables (CV) approach (supposing the use of coherent beams and entangled beam pairs) to the quantum information processing is aimed at the increase of the effectiveness and reliability of the quantum information protocols [1]. Though being the subject to the environmental influence and thus performing always imperfectly, the CV-based quantum systems require the study of the effect the environment has on the quantum information processing schemes which is done by analyzing the perturbance of the corresponding quantum states.

© 2007 IEEE