Observation of large-area matter-wave interference in caustic BEC flow

The ability of atoms to exhibit wave-like interference is one of the hallmark effects of quantum mechanics. While interference patterns based on different internal atomic states are readily exploited in atom-interferometric measurements, the observation of extended matter wave interference patterns based on different motional paths of a single state is far more difficult. This is due to the short wavelengths typically associated with matter waves, and the fact that interatomic interactions can easily affect the dynamics, leading to solitonic excitations.

Here, we present a new experimental geometry that employs caustics to circumvents these difficulties. We observe intricate large-area matter-wave interference fringes in various geometries. Our results include the observation of the famous Pearcey diffraction pattern known from optical interferences.

This work presents a new platform for the study of matter-wave interference and offers interesting analogies to flow observed in other contexts, including 2D electron gases.