Bose-Einstein condensation in large time-averaged optical ring potentials

TL;DR

This paper demonstrates the creation of large, smooth ring traps for Bose-Einstein condensates using time-averaged optical potentials, enabling potential applications in matter wave interferometry and superfluidity studies.

Contribution

It introduces a method to produce smooth, large-diameter ring traps for BECs with optical intensity correction, advancing trapped matter wave interferometry.

Findings

Successfully created smooth ring traps up to 300 μm in diameter

Observed low energy excitations constraining potential smoothness

Good agreement between experimental results and simulations

Abstract

Interferometric measurements with matter waves are established techniques for sensitive gravimetry, rotation sensing, and measurement of surface interactions, but compact interferometers will require techniques based on trapped geometries. In a step towards the realization of matter wave interferometers in toroidal geometries, we produce a large, smooth ring trap for Bose-Einstein condensates using rapidly scanned time-averaged dipole potentials. The trap potential is smoothed by using the atom distribution as input to an optical intensity correction algorithm. Smooth rings with a diameter up to 300 $\mu$m are demonstrated. We experimentally observe and simulate the dispersion of condensed atoms in the resulting potential, with good agreement serving as an indication of trap smoothness. Under time of flight expansion we observe low energy excitations in the ring, which serves to constrain the lower frequency limit of the scanned potential technique. The resulting ring potential will have applications as a waveguide for atom interferometry and studies of superfluidity.