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Ramsey Interferometry Quantifies Spectator-Crosstalk in Silicon Carbide S=3/2 Qudits

Researchers at Gwangju Institute of Science and Technology used broadband Ramsey interferometry to quantify spectator‑crosstalk in silicon‑vacancy (SiV) qudits in 4H‑SiC. The technique mapped off‑resonant microwave‑driven transitions, revealing a deterministic six‑branch structure that matches analytic predictions without any frequency fitting. Numerical time‑domain propagation reproduced the detuning maps, confirming the model’s accuracy. The work provides a practical framework for calibrating pulses, suppressing leakage, or even exploiting spectator lines to improve qudit control and measurement fidelity.