Stabilization of a solid-state spin qubit in a decoherence-protected subspace*

Basal divacancies in silicon carbide (SiC) are solid-state spin systems with excellent spin coherence properties due to a clock transition at zero magnetic field [1,2]. When embedded in a decoherence-protected subspace (DPS) using a microwave dressing drive, the spin becomes highly insensitive to magnetic and electric fluctuations caused by impurities in the surrounding SiC lattice, resulting in record-long spin dephasing times greater than 22 ms [2]. Operation at the zero-field condition is accomplished using vector-magnetic control of the local field guided by analytical models of the DPS ground-state energy levels. Ramsey spectroscopy within the DPS is used to perform feedback that negates the effects of hertz-level shifts to the DPS energy levels that would otherwise introduce spurious dephasing. This demonstration of the coherence measurement of an electron spin qubit in a DPS indicates that utilizing this technique could lead to similar improvements in other systems where long coherence times and fast control are needed.
[1] Miao, K. et al. Sci. Adv. 5 (2019)
[2] Miao, K. et al. Science 369, 1493–1497 (2019)