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. Their extrinsic nature promises easy device integration through nano implantation. Specifically, chromium in the 4+ charge state (Cr⁴⁺) in silicon carbide (SiC) produces an S = 1 ground state and an S = 0 excited state with a strain insensitive near-telecom Λ-like optical-spin interface. In previous demonstrations the ground state spin control was limited by material quality. In this work [1], we study the formation Cr⁴⁺ in a commercial SiC substrate through implantation and annealing, enabling optical and coherent spin characterization. We measure an ensemble optical hole linewidth of 31 MHz, an order of magnitude narrower compared to as-grown samples. Through a detailed investigation of the Cr⁴⁺ governing transition dynamics, we optimize for high readout fidelities (79%). We report T₁ times greater than 1 s at T = 15 K with a T₂^* = 317 ns and a T₂ = 81 μs limited by the ensemble density. These results demonstrate Cr⁴⁺ in SiC to be an optically active spin-qubit for integration within hybrid quantum devices.

[1] B. Diler, et. al. arXiv:1909.08778