Stoichiometric Rare-Earth Materials as a Platform for Quantum Memory and Information Processing

Rare-earth atoms in crystalline solids at cryogenic temperatures are a promising platform for quantum memory and quantum information processing due to their exceptional optical and spin coherence properties, lack of motional dephasing, and potential for use in integrated photonics. A major drawback of these systems is the inhomogeneous broadening of the optical transition, which prevents utilizing the longest-lived spin coherence properties available with rare-earth atoms. This inhomogeneity is due to site-to-site variations of the local electrostatic environment, which shifts the electronic states. The dominant source of this variation is point defects in the crystal, a major contribution coming from the random dopants themselves. Rare-earth materials in which the atoms are stoichiometric in the crystal structure, rather than doped, have demonstrated substantially less broadening due to the lack of this source of disorder. A major challenge is identifying and synthesizing suitable samples with sufficiently large inter-atom spacing to remain in the weakly interacting regime. Here we present initial studies of europium-based stoichiometric materials as a platform for quantum memory devices.