Designing stoichiometric materials with Eu³⁺ for photon-based quantum information storage

Rare-earth cations are a promising platform for quantum information storage because of their long coherence times and well-shielded 4f orbital optical transitions. Though systems under study typically have dilute rare-earth cation concentrations, this leads to inhomogeneity within the structure and thus broadens the linewidth of critical hyperfine transitions. Stoichiometric rare-earth crystals, specifically those with Eu³⁺, offer a promising alternative for finding naturally narrow inhomogeneous linewidth materials. Promising candidates have been selected from experimental and computational databases. Additionally, unrealized stoichiometric compounds with mononuclidic cations and large predicted Eu³⁺ separation have been predicted to be stable with density functional theory energy calculations. Single crystals of several materials, including metal-organic frameworks and oxides, have been grown. Once made, their environmental stability and intrinsic defects are monitored with diffraction and spectroscopy techniques. Cryogenic photoluminescence excitation measurements are then used to probe the linewidth of the important ⁵D₀→⁷F₀ transition of Eu³⁺, revealing critical design factors.

This work is supported by the DOE NQI research center Q-NEXT.