Autofeedback scheme for preservation of macroscopic coherence in microwave cavities

We present a scheme for controlling the decoherence of a linear superposition of two coherent states with opposite phases in a high-$Q$ microwave cavity, based on the injection of appropriately prepared “probe” and “feedback” Rydberg atoms, improving the one presented by D. Vitali et al. [Phys. Rev. Lett. $79$, 2442 (1997)]. In the present scheme, the information transmission from the probe to the feedback atom is directly mediated by a second auxiliary cavity. The detection efficiency for the probe atom is no longer a critical parameter, and the decoherence time of the superposition state can be significantly increased using presently available technology.