Abstract

We report the first observation of the alteration of fundamental atomic radiative processes due to the illumination of atoms with manifestely quantum or nonclassical light. More specifically we have investigated two-photon excitation with squeezed light. Note that while classical excitation from coherent or thermal light sources results in a quadratic dependence of the excitation rate on incident intensity, the quantum correlations of a squeezed field can give rise to an excitation rate with a linear dependence for small squeezed intensities. V³1 In our experiment we have studied the two-photon transition 6S_1/2 —* 6D_5/2 for trapped atomic Cesium W excited by squeezed-vacuum light generated by a nondegenerate optical parametric oscillator (OPO) M with the basic experimental setup shown in Fig. 1. Our measurements have confirmed deviations of the excitation rate from the usual quadratic form and extent into a regime with slope 1.3. For comparison we have shown that in the case of coherent excitation, the rate of excitation remains quadratic throughout the corresponding region of excitation intensities^[1-3]

© 1995 Optical Society of America