Enhanced spin coherence of rubidium atoms in solid parahydrogen*

Alkali atoms trapped in solid parahydrogen are optically addressable and have excellent spin coherence properties. They retain these properties at high spin densities, making them a promising platform for applications such as atomic magnetometry in the solid phase. We have identified the physical mechanism that limits the ensemble T$_2^*$ as electrostatic in nature, and are able to achieve significantly longer T$_2^*$ times by using nonclassical spin superposition states. By contrast, we find the spin-echo T$_2$ is limited by interactions that are magnetic in nature. Progress towards identifying the source of this magnetic decoherence will be discussed.