Atomic Clock Measurements of Quantum Scattering Phase Shifts Spanning Feshbach Resonances at Ultralow Fields

TL;DR

This study employs an atomic fountain clock to precisely measure quantum scattering phase shifts at ultralow energies across Feshbach resonances, comparing results with theoretical models to validate accuracy.

Contribution

It introduces a high-precision measurement technique for quantum scattering phase shifts at ultralow fields and compares these with theoretical predictions to assess model accuracy.

Findings

Excellent agreement between measurements and theory

Small unexplained statistically significant differences

Validated the accuracy of the theoretical model

Abstract

We use an atomic fountain clock to measure quantum scattering phase shifts precisely through a series of narrow, low-field Feshbach resonances at average collision energies below $1\,\mu$K. Our low spread in collision energy yields phase variations of order $\pm \pi/2$ for target atoms in several $F,m_F$ states. We compare them to a theoretical model and establish the accuracy of the measurements and the theoretical uncertainties from the fitted potential. We find overall excellent agreement, with small statistically significant differences that remain unexplained.