Coherent State Preparation and Observation of Rabi Oscillations in a   Single Molecule
  We report on the excitation of single molecules via narrow zero-phonon transitions using short laser pulses. By monitoring the Stokes-shifted fluorescence, we studied the excited state population as a function of the delay time, laser intensity, and frequency detuning. A pi-pulse excitation was demonstrated with merely 500 photons, and 5 Rabi cycles were achieved at higher excitation powers. Our findings are in good agreement with theoretical calculations and provide a first step toward coherent manipulation of the electronic states of single molecules with few photons. 
Ilja Gerhardt and Gert Wrigge and Gert Zumofen and Jaesuk Hwang and   Alois Renn and Vahid Sandoghdar