Scientists observed quantum "rain" for the first time

At the Quantum Mixtures Laboratory of the National Institute of Optics, scientists have for the first time recorded the phenomenon of capillary instability in an unusual medium - an ultra-dilute quantum gas. The work is published in the journal Physical Review Letters (PRL).

Capillary instability, or Plateau-Rayleigh instability, manifests in phenomena such as the breaking of a water jet into droplets or the formation of soap bubbles. It is related to surface tension - the tendency of a liquid to minimize its surface area. For the first time, this classical behavior has been reproduced in a system governed by the laws of quantum mechanics.

At ultra-low temperatures, atoms lose their individuality and behave as a single quantum entity. Under such conditions, it is possible to create so-called quantum droplets - self-sustaining clusters of atoms stabilized by quantum effects. Researchers led by Alessia Burchianti used optical methods to create and observe the evolution of such a droplet from a mixture of ultracold potassium and rubidium atoms.

After being released in an optical waveguide, the droplet stretched into a thin filament, which, upon reaching a critical length, broke up into smaller droplets. Their number depended on the length of the original filament, similar to how a liquid jet breaks up in the macroscopic world.

"We have for the first time described the decay of a quantum droplet as a consequence of capillary instability - such behavior in atomic gases has not been observed before," explained Chiara Fort from the University of Florence.

According to the scientists, the results of the study open the way to creating arrays of quantum droplets that could be used in future quantum technologies.