Parth Sabharwal has completed an extensive study of thermal phase fluctuations appearing in narrow superfluid rings, testing some interesting predictions made by a colleague Ludwig Mathey over a decade ago, and we have submitted a manuscript describing his work to Physical Review A.

Thermal Phase Fluctuations in Narrow Superfluid Rings (arXiv)

Using matter-wave interference, we have investigated thermal phase fluctuations in narrow coplanar, concentric rings of ultracold fermionic superfluids. We found that the correlation length decreases with number density, consistent with theoretical expectations. We also observed that increasing the coupling between the rings leads to greater overall coherence in the system. The phase fluctuations increased with a change from periodic to closed boundary conditions as we applied a potential barrier at one point in a ring. These results are relevant for the implementation of proposals to utilize ultracold quantum gases in large and elongated circuit-like geometries, especially those that require deterministic preparation and control of quantized circulation states.