Universal coherence protection and electrical control of spins in silicon carbide*

Recent advances in material quality have led to the isolation of single optically active divacancy (VV) spin qubits in commercially available silicon carbide (SiC) wafers [1-3]. In particular, basally oriented VVs exhibit excellent spin and optical properties when operated near zero magnetic field. We isolate single kh basal VVs in 4H-SiC, where we demonstrate inhomogeneous spin dephasing times approaching 200 µs and Hahn-echo coherence times >1 ms. We map the excited-state fine structure of the kh VV and find near-transform-limited optical coherence in both time and frequency domains. The high degree of optical coherence allows us to implement gigahertz-frequency light-matter interactions, resulting in electrically controlled Landau-Zener-Stückelberg interferometry with the VV orbital levels [1].

The application of periodic driving to the ground-state spin can augment the coherence properties of an already robust spin qubit. Continuous driving of the kh VV’s spin clock transitions results in dressed spin states that are highly resilient against environmental noise, yielding a qubit embedded in a decoherence-protected subspace (DPS) that is robust to magnetic, electric, and temperature fluctuations [2]. We demonstrate arbitrary spin control in the DPS, allowing us to measure record-long electron spin dephasing times >22 ms – a 10,000-fold improvement over the undriven spin at nonzero magnetic fields. Since only a few key components are needed to achieve such improvements, we expect these techniques to be readily extended to other quantum architectures.

[1] K. C. Miao, et al., Sci. Adv. 5 (2019)
[2] K. C. Miao, et al., Science 369 (2020)
[3] C. P. Anderson*, A. Bourassa*, et al., Science 366 (2019)

In collaboration with C. P. Anderson, S. L. Bayliss, J. P. Blanton, A. Bourassa, A. L. Crook, S. J. Whiteley, G. Wolfowicz, G. Thiering, P. Udvarhelyi, V. Ivády, H. Abe, T. Ohshima, Á. Gali, and D. D. Awschalom.