Square Wave Population Oscillations in a Two-Level Atom

V. A. Kaselskii

Michael W. Noel, W. M. Griffith, Thomas F. Gallagher

We present a detailed experimental study of the frequency-modulated excitation of a two-level atom, using a microwave field to drive transitions between two Rydberg Stark states of potassium. In the absence of a modulation the interaction is the standard model of the Rabi problem, producing sinusoidal oscillations of the population between the two states. In the presence of a frequency modulation of the interacting field, however, the time evolution of the system is significantly modified, producing square wave oscillations of the population, sinusoidal oscillations at a different frequency, or even sinusoidal oscillations built up in a series of stair steps. The three responses described above are each found in a different regime for the frequency of the modulation with respect to the unmodulated Rabi frequency: the low-, high-, and intermediate-frequency regimes, respectively.

V. M. Akulin, É. P. Garsevanishvili

Xiaoyong Li, Guo‐Li Wang, Xiaoxin Zhou

By using the B -spline expansion technique and a model potential of the alkali atoms, the properties of frequency-modulated excitation of Rydberg potassium atoms in a static electric field and a microwave field are investigated by using the time-dependent two-level approach. We successfully reproduce the square wave oscillations in the low frequency, the stair step population oscillations in the intermediate frequency, and the multiphoton transitions in the high frequency with respect to the unmodulated Rabi frequency, which have been observed experimentally by Noel et al. [ Phys. Rev. A 58 2265 (1998) ]. Furthermore, we also numerically obtain the discretized Rabi oscillations predicted in the Landau—Zener accumulation model.

Anatoly S. Pazgalev, N. N. Yakobson

PAUL M. RADMORE