Optimal conversion of Bose condensed atoms into molecules via a Feshbach resonance

TL;DR

This paper uses a genetic algorithm to optimize magnetic field sweeps for converting atomic Bose-Einstein condensates into molecules via Feshbach resonance, significantly improving conversion efficiency over linear sweeps.

Contribution

It introduces a genetic algorithm approach to find optimal magnetic field sweeps, achieving over 95% atom-to-molecule conversion in short times, surpassing traditional linear methods.

Findings

Optimal sweeps yield >95% conversion efficiency

Linear sweeps result in only a few percent conversion

Optimal sweep form is independent of interaction strength and resonance width

Abstract

In many experiments involving conversion of quantum degenerate atomic gases into molecular dimers via a Feshbach resonance, an external magnetic field is linearly swept from above the resonance to below resonance. In the adiabatic limit, the fraction of atoms converted into molecules is independent of the functional form of the sweep and is predicted to be 100%. However, for non-adiabatic sweeps through resonance, Landau-Zener theory predicts that a linear sweep will result in a negligible production of molecules. Here we employ a genetic algorithm to determine the functional time dependence of the magnetic field that produces the maximum number of molecules for sweep times that are comparable to the period of resonant atom-molecule oscillations, $2\pi\Omega_{Rabi}^{-1}$. The optimal sweep through resonance indicates that more than 95% of the atoms can be converted into molecules for sweep times as short as $2\pi\Omega_{Rabi}^{-1}$ while the linear sweep results in a conversion of only a few percent. We also find that the qualitative form of the optimal sweep is independent of the strength of the two-body interactions between atoms and molecules and the width of the resonance.