Damping of local Rabi oscillations in the presence of thermal motion

TL;DR

This paper studies how thermal motion affects the coherence of Rabi oscillations in laser cooled atoms, revealing a decay pattern influenced by temperature and field gradients, with implications for quantum control and sensing.

Contribution

It provides a combined theoretical and experimental analysis of thermal motion effects on Rabi oscillations, introducing an analytical decay model applicable to various atomic configurations.

Findings

Rabi oscillation amplitude decays as exp[-(t/τ)^4]

Coherence time τ decreases with higher temperature and field gradient

Model extends to confined atoms and collisional regimes

Abstract

We investigate both theoretically and experimentally the effect of thermal motion of laser cooled atoms on the coherence of Rabi oscillations induced by an inhomogeneous driving field. The experimental results are in excellent agreement with the derived analytical expressions. For freely falling atoms with negligible collisions, as those used in our experiment, we find that the amplitude of the Rabi oscillations decays with time $t$ as $\exp[-(t/\tau)^4]$, where the coherence time $\tau$ drops with increasing temperature and field gradient. We discuss the consequences of these results regarding the fidelity of Rabi rotations of atomic qubits. We also show that the process is equivalent to the loss of coherence of atoms undergoing a Ramsey sequence in the presence of static magnetic field gradients - a common situation in many applications. In addition, our results are relevant for determining the resolution when utilizing atoms as field probes. Using numerical calculations, our model can be easily extended to situations in which the atoms are confined by a potential or to situations where collisions are important.