Coherence and Coupling of Driven Spins in Silicon Carbide

Selectively interfacing solid-state defect electron spins to desired control mechanisms and quantum systems is an ongoing challenge in quantum science, particularly in the face of ubiquitous environmental noise. We demonstrate a selection of emergent properties in a remarkably coherent solid-state spin system, the silicon carbide divacancy, when subjected to periodic drives. These properties give rise to new interaction channels and substantially increased protection from environmental fluctuations. In particular, we establish electrically driven coherent quantum interference by applying microwave-frequency electric fields to drive the divacancy's highly responsive excited-state orbitals and induce Landau-Zener-Stückelberg interference fringes. When combined with the divacancy's highly coherent spin and optical subsystems, this interaction can serve as the basis for a spin-to-photon interface in the microwave regime. Then, by applying a continuous microwave-frequency drive resonant with two of the three ground-state spin levels of the divacancy, we construct a robust qubit embedded in a decoherence-protected subspace. The qubit is protected from magnetic, electric, and temperature fluctuations, which account for nearly all relevant decoherence channels in the solid state. This culminates in an increase of the qubit's inhomogeneous dephasing time by over four orders of magnitude (to >22 milliseconds), while its Hahn-echo coherence time approaches 64 milliseconds. Both of these developments elevate the silicon carbide divacancy defect above its already promising status as a platform for quantum information processing, and open the door to real-world applications requiring robust and controllable quantum properties in a technologically mature solid-state host.