A trapped ultracold atom force sensor with a $\mu$m-scale spatial resolution

TL;DR

This paper demonstrates a high-resolution quantum force sensor using ultracold rubidium atoms in a vertical lattice, achieving micrometer spatial resolution and high sensitivity to gravitational forces through a Ramsey-Raman interferometer.

Contribution

It introduces a method to maintain high vertical resolution while reducing atomic interactions by adjusting confinement, enhancing sensor sensitivity.

Findings

Achieved micrometer-scale vertical spatial resolution.

Maintained high sensitivity to gravitational force with a relative sensitivity of 5×10⁻⁶ at 1s.

Sensitivity improved to 8×10⁻⁸ after one hour of averaging.

Abstract

We report on the use of an ultracold ensemble of $^{87}$Rb atoms trapped in a vertical lattice as a source for a quantum force sensor based on a Ramsey-Raman type interferometer. We reach spatial resolution in the low micrometer range in the vertical direction thanks to evaporative cooling down to ultracold temperatures in a crossed optical dipole trap. In this configuration, the coherence time of the atomic ensemble is degraded by inhomogeneous dephasing arising from atomic interactions. By weakening the confinement in the transverse direction only, we dilute the cloud and drastically reduce the strength of these interactions, without affecting the vertical resolution. This allows to maintain an excellent relative sensitivity on the Bloch frequency, which is related to the local gravitational force, of $5\times10^{-6}$ at 1\,s which integrates down to $8\times10^{-8}$ after one hour averaging time.