Spin Decoherence Dynamics of Er 3 + in CeO 2 Films

Developing telecom-compatible spin-photon interfaces is essential towards scalable quantum networks. Erbium ions (Er³⁺) exhibit a unique combination of a telecom (1.5 μm) optical transition and an effective spin-1/2 ground state, but identifying a host that enables heterogeneous device integration while preserving long optical and spin coherence remains an open challenge. We explore the potential of Er³⁺:CeO₂ films on silicon and study the Er³⁺ spin coherence, offering low nuclear spin density and the potential for on-chip integration. We demonstrate a 38.8 μs spin coherence, which can be extended to 176.4 μs with dynamical decoupling. Pairing experiments with cluster correlation expansion calculations, we identify spectral diffusion induced by bath Er³⁺ spin flip-flops as the dominant decoherence mechanism and provide pathways to millisecond-scale coherence.