Searching for decoherence-free subspaces in cavity quantum electrodynamics

We construct a model which describes a recently performed experiment [Phys. Rev. A 64, 050301(R) (2001)] in which an entangled state between two modes of a single cavity is built. Environmental effects are taken into account and the results agree with the experimental findings. Moreover, the model predicts, for different conditions of the same experiment, a decoherence-free subspace. These conditions are analyzed and slightly different experiments suggested in order to test its viability.