Atom-interferometric test of the equivalence principle at the $10^{-12}$ level

TL;DR

This paper reports a highly sensitive atom interferometry experiment comparing two rubidium isotopes to test the equivalence principle, achieving a precision of 1.8×10⁻¹² and finding no violation.

Contribution

It introduces a dual-species atom interferometer with 2-second free-fall time that significantly improves the precision of equivalence principle tests.

Findings

Measured Eötvös parameter η = (1.6 ± 1.8 (stat) ± 3.4 (sys)) × 10⁻¹²

Achieved sensitivity of 5.4 × 10⁻¹¹ per √Hz

Demonstrated no violation of the equivalence principle at this precision

Abstract

Does gravity influence local measurements? We use a dual-species atom interferometer with $2\,\text{s}$ of free-fall time to measure the relative acceleration between $^{85}$Rb and $^{87}$Rb wave packets in the Earth's gravitational field. Systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. We find an E\"otv\"os parameter of $\eta = [1.6\; \pm\; 1.8\; \text{(stat)}\; \pm \; 3.4 \; \text{(sys)}] \times 10^{-12}$, consistent with zero violation of the equivalence principle. With a resolution of up to $1.4 \times 10^{-11} \, g$ per shot, we demonstrate a sensitivity to $\eta$ of $5.4 \times 10^{-11}\,/\sqrt{\text{Hz}}$.