Microwave Spin Control of a Tin-Vacancy Qubit in Diamond

The negatively charged tin-vacancy (SnV⁻) center in diamond is a promising solid-state qubit for
applications in quantum networking due to its high quantum efficiency, strong zero phonon emission, and
reduced sensitivity to electrical noise. The SnV⁻ has a large spin-orbit coupling, which allows for long spin
lifetimes at elevated temperatures, but unfortunately suppresses the magnetic dipole transitions desired for
quantum control. Here, by use of a naturally strained center, we overcome this limitation and achieve high-
fidelity microwave spin control. We demonstrate a π-pulse fidelity of up to 99.51 $\pm$ 0.03% and a Hahn-
echo coherence time of T$_2$ $^{echo}$ = 170.0 $\pm$ 2.8 μs, both the highest yet reported for SnV− platform. This
performance comes without compromise to optical stability, and is demonstrated at 1.7 K where ample
cooling power is available to mitigate drive-induced heating. These results pave the way for SnV⁻ spins to
be used as a building block for future quantum technologies.