Optically Active Point Defects in 4H–SiC: Identification of Microscopic Mechanisms and Prospects for Quantum Applications

Abstract Optically active point defects in 4H‐polytype silicon carbide (4H–SiC) are promising solid‐state platforms for quantum technologies, offering long spin coherence times, near‐infrared optical transitions, and compatibility with mature semiconductor processing. This review surveys benchmark qubit candidates such as the divacancy and silicon vacancy, alongside unresolved systems including those associated with AB‐lines and PL5/PL6. The material's strategic advantages and the experimental methods—photoluminescence, optically detected magnetic resonance, electron spin resonance, electron nuclear double resonance, and isotope substitution—that enable defect identification and spin‐photon interface development are highlighted. Computational approaches, including hybrid‐functional theory and constrained density functional theory, are discussed for predicting formation energies, zero‐phonon lines, and spin‐Hamiltonian parameters. Defect‐engineering routes are also examined, such as irradiation, implantation, and laser writing, highlighting annealing protocols that govern defect creation and migration. By consolidating insights from both established and unresolved defect families, this review emphasizes the dual challenge and opportunity of advancing defect identification, engineering, and integration. The outlook highlights the need for refined spectroscopic and computational tools to resolve the microscopic origins of enigmatic centers, as well as strategies to stabilize and control their spin and optical properties. Together, these directions chart a pathway for 4H–SiC to evolve from a promising host material into a scalable platform for next‐generation quantum technologies.