Understanding the dopant-driven impact on electronic and crystal structure of erbium-doped oxides for quantum memory

Quantum communication networks rely on qubits, such as photons, for secure long-distance communication. High-fidelity rare-earth ion (REI) memory systems, especially erbium (Er³⁺) in oxide hosts with C-band emission properties, are crucial for synchronizing entanglement for signal amplification in quantum networks [1,2]. Oxides offer growth simplicity, CMOS compatibility, and long coherence times. However, embedding Er³⁺ introduces defects, disrupting the host lattice and resulting in photoluminescence linewidth and lifetime variations in Er-doped oxide films with unclear causes [3,4]. In this work, we employed synchrotron-based X-ray tools, including X-ray absorption spectroscopy and diffraction, to investigate Er-doped titanium oxides electronic and crystal structures as doping levels vary. This information is crucial for controlling the tunability of excited state lifetimes and rare-earth defect linewidths to mitigate decoherence.