Optical Properties of Rubidium Atoms Trapped in Cryogenic Neon and Parahydrogen Solids*

The development of single-atom quantum sensors necessitates long coherence times and the ability to control and detect the states of single atoms. Previous work has shown that rubidium atoms trapped in solid parahydrogen have favorable spin coherence times, however optical fluorescence properties were untested. In this work, we investigate rubidium atoms that are trapped in cryogenic neon and parahydrogen solids. We find that Rb fluoresces efficiently when trapped in neon, while we find no evidence of it fluorescing in parahydrogen. We also find that Rb atoms trapped in neon can be optically cycled billions of times with little evidence of bleaching. Other key optical properties of both systems are discussed.