Inhomogeneous Light Shift Effects on Atomic Quantum State Evolution in Non-Destructive Measurements

TL;DR

This paper investigates how inhomogeneous light shifts affect atomic quantum state evolution during non-destructive measurements, demonstrating experimental analysis and methods to reverse dephasing effects using spin echo techniques.

Contribution

It introduces a simple model for inhomogeneous light shifts and demonstrates how spin echo can mitigate their effects in non-destructive atomic measurements.

Findings

Inhomogeneous light shifts cause measurable dephasing in atomic states.

The simple light shift model accurately describes experimental data.

Spin echo techniques can reverse inhomogeneous phase shifts.

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 nonuniform 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. 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.