  We report a study on the ultrafast coherent population oscillations (UCPO) in
two level atoms induced by the frequency modulated few-cycle optical pulse
train. The phenomenon of UCPO is investigated by numerically solving the
optical Bloch equations beyond the rotating wave approximation. We demonstrate
that the quantum state of the atoms and the frequency of UCPO may be controlled
by controlling the number of pulses in the pulse trains and the pulse
repetition time respectively. Moreover, the robustness of the population
inversion against the variation of the laser pulse parameters is also
investigated. The proposed scheme may be useful for the creation of atoms in
selected quantum state for desired time duration and may have potential
applications in ultrafast optical switching.
