Coherent control and high-fidelity readout of chromium ions in commercial silicon carbide

Transition metal ions provide a rich set of optically active defect spins in wide bandgap semiconductors. Chromium (Cr⁴⁺) in silicon-carbide (SiC) produces a spin-1 ground state with a narrow, spectrally isolated, spin-selective, near-telecom optical interface. However, previous studies were hindered by material quality resulting in limited coherent control. In this work, we implant Cr into commercial 4H-SiC and show optimal defect activation after annealing above 1600 °C. We measure an ensemble optical hole linewidth of 31 MHz, an order of magnitude improvement compared to as-grown samples. An in-depth exploration of optical and spin dynamics reveals efficient spin polarization, coherent control, and readout with high fidelity (79%). We report T₁ times greater than 1 s at cryogenic temperatures (15 K) with a T₂ ^* = 317 ns and a T₂ = 81 μs, where spin dephasing times are currently limited by spin–spin interactions within the defect ensemble. Our results demonstrate the potential of Cr⁴⁺ in SiC as an extrinsic, optically active spin qubit.