Coherent mechanical driving of chromium ion spins in commercial silicon carbide

Transition metal ions provide a rich set of defect-bound spin qubits in wide bandgap semiconductors with an optical interface and are promising candidates for hybrid quantum systems. For example, chromium in the 4+ charge state (Cr⁴⁺) in 4H silicon carbide (4H-SiC) produces a spin-1 ground state with T₁ times longer than a second below 15 K and a spin-0 first excited state. Optical transitions between the two states form a Λ-like system, with spin selective optical transitions insensitive to strain. The ground state spins, however, are expected to be highly strain susceptible. To test this, we use a Cr implanted commercial 4H-SiC substrate, with a fabricated surface acoustic wave resonator. Despite the fact that the defects are only 100 nm below the highly processed sample surface, we observe narrow optical transitions, allowing for spin sublevel addressability. We use this interface to characterize coherent spin-phonon interactions within the device. Our results demonstrate the potential of transition metal ion based qubits for hybrid quantum architectures.