Barium-based Rydberg atom quantum technologies with long Rydberg coherence

Abstract

The short Doppler-limited coherence time of the laser-excited Rydberg state, usually orders of magnitude shorter than the lifetime of the Rydberg state, hinders the Rydberg-mediated quantum technologies. Here, we show that a 649~nm~$-$~658~nm two-photon excitation of the $6sng~^1G_4$ Rydberg state from a long-lived d-orbital clock state of barium can be achieved with a two-photon wavevector that is tiny, which effectively removes the Doppler-limited decoherence. Moreover, the $6sng~^1G_4$ Rydberg state has strong dipole-dipole interaction due to small Förster defect with nearby Rydberg states and possesses long radiative lifetime. These can benefit quantum computing based on individually trapped neutral atoms, and can enable long-lived Rydberg polaritons in atomic media, which brings fresh opportunities in all-optical quantum information.