Nuclear spins of noble gases feature extremely long coherence times but are inaccessible to optical photons. Here we realize a coherent interface between light and noble-gas spins that is mediated by alkali atoms. We demonstrate the optical excitation of the noble-gas spins and observe the coherent back-action on the light in the form of high-contrast two-photon spectra. We report on a record two-photon linewidth of 5±0.7 mHz (millihertz) above room-temperature, corresponding to a one-minute coherence time. This experiment provides a demonstration of coherent bi-directional coupling between light and noble-gas spins, rendering their long-lived spin coherence accessible for manipulations in the optical domain.
@article{arxiv.2102.00229,
title = {Coupling light to a nuclear spin gas with a two-photon linewidth of five millihertz},
author = {Or Katz and Roy Shaham and Ofer Firstenberg},
journal= {arXiv preprint arXiv:2102.00229},
year = {2021}
}