First-principles investigation of Er³⁺-doped CeO₂ as a solid-state spin qubit platform

Er³⁺-doped CeO₂ is a promising spin qubit platform for quantum communication networks, due to the sharp optical transitions of Er³⁺ in the telecom-C band, the possibility of data storage in ¹⁶⁷Er nuclear spins, and the low nuclear spin concentration of CeO₂. Recent experimental investigations demonstrate a homogeneous linewidth of 440 kHz and spin coherence time (T₂) of 0.66 μs at 4 K, which are promising properties. However, the measured linewidth is larger than the lifetime-limited homogeneous broadening of Er³⁺ and the measured spin T₂ is larger than the predicted spin T₂ in CeO₂ [1]. Hence, it is important to investigate the prevalent decoherence mechanisms that lead to optical and spin broadening. Using hybrid density functional theory (DFT) and time-dependent DFT, we report the many-body electronic structure and excited-state properties of Er³⁺-doped CeO₂. We investigate different decoherence mechanisms, including non-radiative decay and charge diffusion due to the surrounding oxygen vacancies, polarons, and their complexes with Er³⁺. Our results provide insight into the predominant decoherence pathways in this system, as well as data that can be used in noise models. Importantly, our framework can be extended to investigate Er³⁺ in other systems of keen interest, e.g., CaWO₄ and Si.

[1] J. Zhang et al., npj Quantum Inf, 2024; G. Grant et al., APL Mater 2024



Work supported by AFOSR CFIRE project, DOE/BES MICCoM center, and Argonne LDRD.