Atom radio-frequency interferometry

TL;DR

This paper demonstrates a novel atom interferometer using Rydberg states in cesium to measure RF wave phase and amplitude with high sensitivity and spatial resolution, without external RF references.

Contribution

It introduces a new atomic interferometry technique utilizing internal atomic states for RF phase and amplitude measurement, eliminating the need for external RF references.

Findings

Achieved RF phase measurement sensitivity of 2 mrad.

Demonstrated RF phase and amplitude measurements with sub-millimeter optical spatial resolution.

Constructed interferometric loops in cesium atom internal states for RF sensing.

Abstract

We realize and model a Rydberg-state atom interferometer for measurement of phase and intensity of radio-frequency (RF) electromagnetic waves. A phase reference is supplied to the atoms via a modulated laser beam, enabling atomic measurement of the RF wave's phase without an external RF reference wave. The RF and optical fields give rise to closed interferometric loops within the atoms' internal Hilbert space. In our experiment, we construct interferometric loops in the state space $\{ 6P_{3/2}, 90S_{1/2}, 91S_{1/2}, 90P_{3/2} \}$ of cesium and employ them to measure phase and intensity of a 5 GHz RF wave in a room-temperature vapor cell. Electromagnetically induced transparency on the $6S_{1/2}$ to $6P_{3/2}$ transition serves as an all-optical interferometer probe. The RF phase is measured over a range of $\pi$, and a sensitivity of 2 mrad is achieved. RF phase and amplitude measurements at sub-millimeter optical spatial resolution are demonstrated.