Observation of the Rabi-resonance spectrum

By use of a double-resonance technique, a spectrum of Rabi resonances has been observed. These resonances are enhancements in the dynamic response of a quantum system's population to rapid changes in the phase of a perturbing electromagnetic field. Theoretically, it is shown that the appearance of a spectrum, as opposed to a single Rabi resonance, is due to the fact that the phase of the field changes discretely by {π} radians, rather than sinusoidally. In the presence of {π}-radian phase changes, the quantum system's dynamic response is found to be similar to a damped harmonic oscillator driven by a {δ}-function force term. In this harmonic-oscillator approximation the Rabi-resonance spectrum arises naturally, resulting from a resonant enhancement of the atomic coherence.