Nanotesla Magnetometry with the Silicon Vacancy in Silicon Carbide

Silicon carbide is a promising host material for spin-defect-based quantum sensors owing to its commercial availability and established techniques for electrical and optical microfabricated device integration. The negatively charged silicon vacancy is one of the leading spin defects studied in silicon carbide owing to its near-telecom photoemission, high spin number, and nearly temperature-independent ground-state zero-field splitting. We report the realization of nanotesla shot-noise-limited ensemble magnetometry based on optically detected magnetic resonance with the silicon vacancy in $4H$ silicon carbide. By coarsely optimizing the anneal parameters and minimizing power broadening, we achieve a sensitivity of $50\phantom{\rule{0.2em}{0ex}}\mathrm{nT}/\sqrt{\mathrm{Hz}}$ and a theoretical shot-noise-limited sensitivity of $3.5\phantom{\rule{0.2em}{0ex}}\mathrm{nT}/\sqrt{\mathrm{Hz}}$. This is accomplished without utilizing complex photonic engineering, control protocols, or applying excitation powers greater than a watt. This work demonstrates that the silicon vacancy in silicon carbide provides a low-cost and simple approach to quantum sensing of magnetic fields.