Deterministic and Scalable Coupling of Single 4H‐SiC Spin Defects into Bullseye Cavities

ABSTRACT Silicon carbide (SiC) has attracted significant attention as a promising quantum material due to its ability to host long‐lived, optically addressable color centers with solid‐state photonic interfaces. The CMOS compatibility of 4H‐SiCOI (silicon‐carbide‐on‐insulator) makes it an ideal platform for integrated quantum photonic devices and circuits. However, the deterministic integration of single spin defects into high‐performance photonic cavities on this platform has remained a key challenge. In this work, we demonstrate the deterministic and scalable coupling of both ensemble (PL4) and single PL6 spin defects into monolithic bullseye cavities on the 4H‐SiCOI platform. By tuning the cavity resonance, we achieve a 40‐fold enhancement of the zero‐phonon line (ZPL) intensity from ensemble PL4 defects, corresponding to a Purcell factor of approximately 5.0. For deterministically coupled single PL6 defects, we observe a threefold increase in the saturated photon count rate, confirm single‐photon emission, and demonstrate coherent control of the spin state through optically detected magnetic resonance (ODMR), resonant excitation, and Rabi oscillations. These advancements establish a viable pathway for developing scalable, high‐performance SiC‐based quantum photonic circuits.