Abstract
Various parameters of a trapped collection of cold and ultracold atoms can be determined non-destructively by measuring the phase shift of an off-resonant probe beam, caused by the state-dependent index of refraction of the atoms. The dispersive light–atom interaction, however, gives rise to a differential light shift (ac Stark shift) between the atomic states which, for a non-uniform probe intensity distribution, causes an inhomogeneous dephasing between the atoms. In this paper, we investigate the effects of this inhomogeneous light shift in non-destructive measurement schemes in cold caesium. We interpret our experimental data on dispersively probed Rabi oscillations and Ramsey fringes in terms of a simple light shift model which is shown to describe the observed behavior well. Furthermore, we show that by using spin echo techniques, the inhomogeneous phase shift distribution between the two clock levels can be reversed.
Highlights
In the present paper we analyze these inhomogeneous effects by studying the evolution of clock–state Rabi oscillations, and we perform Ramsey spectroscopy measurements to further characterize the dephasing
We use a dispersive phase shift measurement to non– destructively probe the populations of the clock states in a cold Cs ensemble when subjected to near resonant microwave pulses
The strong dependence of the Rabi oscillation envelope on the probe pulse photon numbers — causing a differential light shift between the clock states and adding a relative phase between the clock states — can only be explained by the inhomogeneity of the light– atom interaction, which is intrinsic to the experimental setup
Summary
P. Windpassinger et al.: Inhomogeneous Light Shift Effects on Quantum State Evolution. The interrogation of the (inhomogeneous) sample induces an inhomogeneous light shift across the atomic sample, which is detected with a non–uniform detection efficiency. In the present paper we analyze these inhomogeneous effects by studying the evolution of clock–state Rabi oscillations, and we perform Ramsey spectroscopy measurements to further characterize the dephasing. We investigate the reversibility of the probe–introduced dephasing with spin echo techniques
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