Five-second coherence of a single spin with single-shot readout in silicon carbide*

The neutral divacancy (VV⁰) in silicon carbide (SiC) is a spin defect that boasts a near-infrared spin-photon interface [1], long coherence times [2], and is hosted in a material that provides opportunities for wafer-scale semiconductor device engineering. Despite these advantages, single-shot readout (SSR)--deterministic measurement of the quantum state--has long been an outstanding hurdle for defect spins in SiC. Here, we present a demonstration of SSR of a single VV⁰ using spin-to-charge conversion (SCC) [3]. This SCC technique maps the spin state onto a long-lived charge state that can be optically read out. Using this technique, we achieve over 80% readout fidelity of the spin state without pre- or post-selection and harness the high signal-to-noise ratio of the readout to measure ultralong spin coherence times. We apply pulsed dynamical decoupling sequences to an isotopically purified host material and use SCC to measure single-spin T₂ times exceeding five seconds, over two orders of magnitude greater than previously reported for this system. The SSR demonstrated here unlocks key capabilities for SiC-based systems, such as entanglement distribution and enhanced ac-sensitivity in quantum sensing schemes. These results also pave the way for integration of defects into single-charge sensitive, classical electrical devices.

[1] D. J. Christle et al., Phys. Rev. X. 7, 1–12 (2017).

[2] H. Seo et al., Nat. Comm. 7, 12935 (2016).

[3] C. P. Anderson, E. O. Glen et al., arXiv:2110.01590v2 (5 October 2021)