Minimally destructive, Doppler measurement of a quantized, superfluid flow

TL;DR

This paper introduces a minimally destructive in-situ Doppler-based method to measure persistent currents in superfluid Bose-Einstein condensates, enabling precise detection of flow velocities relevant for atomtronic applications.

Contribution

It presents a novel Doppler shift measurement technique for quantifying superfluid flow in a ring-shaped condensate, advancing non-invasive flow detection methods.

Findings

Successfully measured persistent currents via phonon mode precession

Demonstrated minimally destructive in-situ flow measurement

Potential applications in atomtronic devices

Abstract

The Doppler effect, the shift in the frequency of sound due to motion, is present in both classical gases and quantum superfluids. Here, we perform an in-situ, minimally destructive measurement, of the persistent current in a ring-shaped, superfluid Bose-Einstein condensate using the Doppler effect. Phonon modes generated in this condensate have their frequencies Doppler shifted by a persistent current. This frequency shift will cause a standing-wave phonon mode to be "dragged" along with the persistent current. By measuring this precession, one can extract the background flow velocity. This technique will find utility in experiments where the winding number is important, such as in emerging `atomtronic' devices.