来源：ACS Publications
Nanocrystalline CeO2 is a chemically tunable wide-bandgap host lattice of interest for quantum information technologies due to its ability to accommodate optically- and spin-active defects. Here, we investigate CeO2 nanocrystals as hosts for near-infrared-compatible Yb3+ ions as optically active spin quantum bits (qubits). We characterize the as-synthesized Yb3+-doped CeO2 nanocrystals (0.01–10% Yb) by photoluminescence, which reveals short photoluminescence lifetimes dominated by nonradiative decay arising from surface and Ce3+-related defects. Thermal annealing at 700 °C increases crystalline domain sizes (from ∼7 nm to ∼20 nm) and reduces the concentration of Ce3+ defects, yielding an enhancement in excited-state lifetimes. Low-temperature optical spectroscopy reveals at least two distinct Yb3+ lattice sites with cubic and trigonal symmetries, and a ∼5-fold difference in photoluminescence lifetimes between the two sites. Continuous-wave EPR measurements support these site assignments, while pulse EPR measurements further show that annealing the nanocrystals nearly doubles the spin–lattice relaxation time (T1) from 33.9 to 62.7 μs at 0.08% Yb. Phase memory times, however, remain relatively constant, indicating that coherence is limited by dephasing mechanisms (e.g., slowly fluctuating local fields) rather than by spin–lattice relaxation. Collectively, these results establish defect mitigation, rather than dopant identity alone, as a bottleneck in realizing nanocrystalline CeO2 as a viable quantum host. This work provides quantitative benchmarks for optical and spin coherence in CeO2:Yb3+ nanocrystals and highlights defect engineering as a critical pathway toward scalable rare earth-based qubits.