Coupling light to a nuclear spin gas with a two-photon linewidth of five millihertz

Abstract

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.

Strong coupling of alkali spins to noble-gas spins with hour-long coherence time

“…The hybridization of optically-accessible alkali spins and long-lived noble-gas spins opens several intriguing possibilities. One route motivated by quantum information applications is using the alkali spins as mediators between photons and noble-gas spins [34]. The strong spin-spin coupling can improve the performance of such applications by enhancing the indirect coupling to photons.…”

“…It is employed for readout of noblegas-based sensors and for inherent suppression of sensitivity to magnetic fields [2][3][4]9]. Recently, we used alkali spins as off-resonant mediators to couple light to noble-gas spins bidirectionally [34]. However, these works have been limited to the regime of detuned or overdamped coupling, with the alkali spin relaxation exceeding the coupling strength to the noble-gas spins.…”