Observation of quantum droplets in a strongly dipolar Bose gas

TL;DR

This paper reports the experimental observation of stable quantum droplets in a strongly dipolar Bose gas, demonstrating that quantum fluctuations can stabilize attractive interactions and lead to phase-coherent many-body states.

Contribution

First experimental evidence showing quantum fluctuations stabilize dipolar Bose gases into stable, phase-coherent quantum droplets against mean-field collapse.

Findings

Quantum droplets contain about 800 atoms.

Quantum fluctuations prevent mean-field collapse.

Droplets exhibit phase coherence through interference.

Abstract

Quantum fluctuations are the origin of genuine quantum many-body effects, and can be neglected in classical mean-field phenomena. Here we report on the observation of stable quantum droplets containing $\sim$ 800 atoms which are expected to collapse at the mean-field level due to the essentially attractive interaction. By systematic measurements on individual droplets we demonstrate quantitatively that quantum fluctuations stabilize them against the mean-field collapse. We observe in addition interference of several droplets indicating that this stable many-body state is phase coherent.