Observation of interference between two molecular Bose-Einstein condensates

TL;DR

This paper reports the observation of interference patterns between two molecular Bose-Einstein condensates of fermionic lithium atoms, demonstrating quantum coherence and the effects of interactions on condensate overlap.

Contribution

It provides the first direct observation of interference between molecular BECs and explores how interactions affect their coherence and overlap.

Findings

Clear interference pattern observed between condensates

Interference only present in the condensate fraction

Strong interactions suppress interference and prevent penetration

Abstract

We have observed interference between two Bose-Einstein condensates of weakly bound Feshbach molecules of fermionic $^6$Li atoms. Two condensates are prepared in a double-well trap and, after release from this trap, overlap in expansion. We detect a clear interference pattern that unambiguously demonstrates the de Broglie wavelength of molecules. We verify that only the condensate fraction shows interference. For increasing interaction strength, the pattern vanishes because elastic collisions during overlap remove particles from the condensate wave function. For strong interaction the condensates do not penetrate each other as they collide hydrodynamically.