Fast transitionless expansions of cold atoms in optical Gaussian beam traps

TL;DR

This paper compares three methods for rapidly expanding cold atoms in optical traps, highlighting inverse engineering as the most effective in minimizing motional excitation and analyzing perturbation effects.

Contribution

It introduces and compares inverse engineering, bang-bang, and adiabatic methods for fast atomic expansion, emphasizing the advantages of inverse engineering in optical Gaussian-beam traps.

Findings

Inverse engineering outperforms other methods in minimizing excitation.

Increasing laser beam waist mitigates perturbations.

Perturbations include anharmonicity, coupling, and frequency mismatch.

Abstract

We study fast expansions of cold atoms in a three-dimensional Gaussian-beam optical trap. Three different methods to avoid final motional excitation are compared: inverse engineering using Lewis-Riesenfeld invariants, which provides the best overall performance, a bang-bang approach, and a fast adiabatic approach. We analyze the excitation effect of anharmonic terms, radial-longitudinal coupling, and radial-frequency mismatch. In the inverse engineering approach these perturbations can be suppressed or mitigated by increasing the laser beam waist.