Optically Active Yb3+ Spin Defects in Cerium Oxide Nanocrystals

Controlling defects in wide‑bandgap nanomaterials is central to building scalable quantum systems. In this work, we demonstrated optically active and spin-bearing Yb³⁺ defects in CeO₂ nanocrystals, establishing quantitative benchmarks for excited‑state optical lifetimes, spin‑lattice relaxation (T₁), and spin coherence (T_m). We identified two distinct Yb³⁺ lattice sites with ~5× lifetime differences, and we directly linked these to local defect environments. We showed that annealing at 700 °C reduces Ce³⁺and oxygen‑vacancy defects, nearly doubling the T₁ spin lifetime and improving optical lifetimes.

This work establishes defect mitigation as the key bottleneck for realizing rare‑earth spin qubits in colloidal nanocrystal hosts and establishes CeO₂:Yb³⁺ nanocrystals as a platform for future IRG efforts in rare‑earth qubits. It directly supports the IRG mission to integrate synthesis, defect engineering, and quantum characterization to create next‑generation spin-photon interfaces based on nanocrystals. It demonstrates the power of MEM-C-enabled collaboration (synthetic chemistry + spectroscopy + EPR) to uncover structure-property relationships essential for scalable quantum technologies.