Quantum Feedback for Protection of Schroedinger-cat states
  We review the use of quantum feedback for combatting the decoherence of Schroedinger-cat-like states in electromagnetic cavities, with special emphasys on our recent proposal of an automatic mechanism based on the injection of appropriately prepared ``probe'' and ``feedback'' Rydberg atoms. In the latter 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 linear superposition state can be significantly increased using presently available technology. 
Mauro Fortunato (1), Paolo Tombesi (1), David Vitali (1), and   Jean-Michel Raimond (2) ((1) University of Camerino, Italy, ...