Nonlinear scattering of atomic bright solitons in disorder

TL;DR

This paper demonstrates nonlinear scattering behavior of atomic bright solitons in a disordered 1D environment, showing collective reflection or transmission distinct from non-interacting particles, with implications for quantum superpositions and interferometry.

Contribution

It provides the first experimental comparison of nonlinear soliton scattering with non-interacting particles in disorder, highlighting collective effects and sensitivity to initial conditions.

Findings

Solitons tend to be either fully reflected or transmitted, unlike independent particles.

Strong fluctuations in reflected fraction depend on soliton velocity and experimental conditions.

Mean-field simulations reproduce the observed nonlinear scattering behavior.

Abstract

We observe nonlinear scattering of 39 K atomic bright solitons launched in a one-dimensional (1D) speckle disorder. We directly compare it with the scattering of non-interacting particles in the same disorder. The atoms in the soliton tend to be collectively either reflected or transmitted, in contrast with the behavior of independent particles, thus demonstrating a clear nonlinear effect in scattering. The observed strong fluctuations in the reflected fraction, between zero and 100%, are interpreted as a consequence of the strong sensitivity of the system to the experimental conditions and in particular to the soliton velocity. This behavior is reproduced in a mean-field framework by Gross-Pitaevskii simulations, and mesoscopic quantum superpositions of the soliton being fully reflected and fully transmitted are not expected for our parameters. We discuss the conditions for observing such superpositions, which would find applications in atom interferometry beyond the standard quantum limit.