UC Berkeley

Matter wave interferometry with laser pulses has become a powerful tool for precision measurement. Optical resonators, meanwhile, are an indispensable tool for control of laser beams. We have combined these two components, and built the first atom interferometer inside of an optical cavity. This apparatus was then used to examine interactions between atoms and a small, in-vacuum source mass. We measured the gravitational attraction to the source mass, making it the smallest source body ever probed gravitationally with an atom interferometer. Searching for additional forces due to screened fields, we tightened constraints on certain dark energy models by several orders of magnitude. Finally, we measured a novel force mediated by blackbody radiation for the first time.

Utilizing technical benefits of the cavity, we performed interferometry with adiabatic passage. This enabled new interferometer geometries, large momentum transfer, and interferometers with up to one hundred pulses. Performing a trapped interferometer to take advantage of the clean wavefronts within the optical cavity, we performed the longest duration spatially-separated atom interferometer to date: over ten seconds, after which the atomic wavefunction was coherently recombined and read out as interference to measure gravity. This work demonstrates the feasibility and utility of bringing a cavity to atom interferometry.