Continuous variable noise-free states in correlated quantum noisy channels

We explicitly compute the evolution of the density operator of a two-mode electromagnetic field when the influence of the thermal fluctuation of the vacuum is common for both modes. From this result, we give an example in which the bundle of quantum noisy channels turns out to be noiseless for the special type of signal states due to the correlation.Comment: revtex4, no figures, The Seventh International Conference on Quantum Communication, Measurement and Computing, Glasgow, UK, from 25th to 29th July 2004. To appear in the AIP Conference Proceeding