Autofeedback scheme for preservation of macroscopic coherence in microwavecavities

We present a scheme for controlling the decoherence of a linear superpositi on of two coherent states with opposite phases in a high-e microwave cavity , based on the injection of appropriately prepared "probe" and "feedback" R ydberg atoms, improving the one presented by D. Vitali et al. [Phys. Rev. L ett. 79, 2442 (1997)]. In the present scheme, the information transmission from the probe to the feedback atom is directly mediated by a second auxili ary cavity. The detection efficiency for the probe atom is no longer a crit ical parameter, and the decoherence time of the superposition state can be significantly increased using presently available technology. [S1050-2947(9 9)11108-9].