Measuring gravity by holding atoms

TL;DR

This paper advances atom interferometry by optimizing lattice-based measurements, achieving high precision in gravity measurement, and demonstrating potential for probing fundamental physics phenomena.

Contribution

It introduces a method to enhance lattice interferometer sensitivity and systematically suppress errors, enabling high-precision gravity measurements surpassing free-fall techniques.

Findings

Achieved a measurement accuracy of 6.2 nm/s^2, four times better than free-fall methods.

Successfully measured the attraction of a miniature source mass.

Ruled out certain dark energy theories within their parameter space.

Abstract

Despite being the dominant force of nature on large scales, gravity remains relatively elusive to experimental measurement. Many questions remain, such as its behavior at small scales or its role in phenomena ascribed to dark matter and dark energy. Atom interferometers are powerful tools for probing Earth's gravity, the gravitational constant, dark energy theories and general relativity. However, they typically use atoms in free fall, which limits the measurement time to only a few seconds, and to even briefer intervals when measuring the interaction of the atoms with a stationary source mass. Recently, interferometers with atoms suspended for as long as 70 seconds in an optical lattice have been demonstrated. To keep the atoms from falling, however, the optical lattice must apply forces that are billion-fold as strong as the putative signals, so even tiny imperfections reduce sensitivity and generate complex systematic effects. As a result, lattice interferometers have yet to demonstrate precision and accuracy on par with their free fall counterparts and have yet to be used for precision measurement. Here, we optimize the sensitivity of a lattice interferometer and use a system of signal inversions and switches to suppress and quantify systematic effects. This enables us to measure the attraction of a miniature source mass, ruling out the existence of screened dark energy theories over their natural parameter space. More importantly, the combined accuracy of $6.2~\rm{nm/s}^2$ is four times as good as the best similar measurements with freely falling atoms, demonstrating the advantages of lattice interferometry in fundamental physics measurements. Further upgrades may enable measuring forces at sub-millimeter ranges, the gravitational Aharonov-Bohm effect and the gravitational constant, compact gravimetry, and testing whether the gravitational field itself has quantum properties.