Harnessing rare-earth ions in oxides for quantum networks requires integration with bright emitters in III-V semiconductors, but local disorder and interfacial noise limit their optical coherence. Here, we investigate the microscopic origins of the ensemble spectrum in Er3+:TiO2 epitaxial thin films on GaAs and GaSb substrates. Ab initio calculations combined with noise-Hamiltonian modeling and Monte Carlo simulations quantify the effects of interfacial and bulk spin noise and local strain on erbium crystal-field energies and inhomogeneous linewidths. Photoluminescence excitation spectroscopy reveals that Er3+ ions positioned at increasing distances from the III-V/oxide interface produce a systematic blue shift of the Y1→Z1 transition, consistent with strain relaxation predicted by theory. Thermal annealing produces a compensating redshift and linewidth narrowing, isolating the roles of oxygen-vacancy and gallium-diffusion noise. These results provide microscopic insight into disorder-driven decoherence, offering pathways for precise control of hybrid quantum systems for scalable quantum technologies.
@article{arxiv.2511.19668,
title = {Quantum Coherence of Rare-Earth Ions in Heterogeneous Photonic Interfaces},
author = {Henry C. Hammer and Hassan A. Bukhari and Yogendra Limbu and Brett M. Wasick and Christopher Rouleau and Michael E. Flatté and Durga Paudyal and Denis R. Candido and Ravitej Uppu},
journal= {arXiv preprint arXiv:2511.19668},
year = {2025}
}