Observation of the Vacuum-Rabi Spectrum for One Trapped Atom
  The transmission spectrum for one atom strongly coupled to the field of a high-finesse optical resonator is observed to exhibit a clearly resolved vacuum-Rabi splitting characteristic of the normal modes in the eigenvalue spectrum of the atom-cavity system. A new Raman scheme for cooling atomic motion along the cavity axis enables a complete spectrum to be recorded for an individual atom trapped within the cavity mode, in contrast to all previous measurements in cavity QED that have required averaging over many atoms. 
A. Boca, R. Miller, K. M. Birnbaum, A. D. Boozer, J. McKeever, and H.   J. Kimble