Creation and coherent control of Cr⁴⁺ spin ensembles in commercial silicon carbide

Optically active defect spins in solid-state materials, such as the nitrogen-vacancy center in diamond and vacancy complexes in silicon carbide (SiC), are an important resource for quantum technologies. Their electronic spins show promise as long-lived qubits with optical addressability. Recent work in 4H-SiC demonstrates the potential of transition metal defects [1]. In particular, Cr⁴⁺ has a spin-1 electronic ground state with long T₁ times at cryogenic temperatures. High zero phonon line emission (73%), and narrow inhomogeneous optical ensemble linewidths (<7 GHz) of Cr⁴⁺ enable optical spin initialization as well as readout using resonant near-infrared excitation. Here, we demonstrate that ion implantation followed by annealing at temperatures up to 1900 ^oC results in Cr⁴⁺ ensembles with spectral-hole linewidths that are an order of magnitude narrower compared to as-grown samples. Improvements in material preparation and photon collection allow for coherent control and measurement of the spin properties of Cr⁴⁺ defects, highlighting their potential for quantum information processing.

[1] W. F. Koehl, et. al. Phys. Rev. B 95, 035207 (2017)