Coherent 13C Nuclear Spin State Readout Driven by Spin Density Mediated NV Centers in Isotopically Purified 6H-28SiC.

Here we study the hyperfine interactions of the nitrogen-vacancy (NV) centers in a 6H-SiC crystal with remote 13C nuclear spins using high-resolution EPR and ENDOR spectroscopy, with c-axis of the crystal aligned parallel to an external magnetic field of 3.4 T. Fine-tuned Mims pulse sequences, combined with isotopic enrichment by nonmagnetic 28Si, yield a high nuclear spin readout contrast of η ≈ 35% for detecting 13C NMR transitions. The extracted hyperfine interaction constants indicate that the NV electron spin couples to 13C nuclei located in the fifth or sixth coordination shells. Coherent 13C nuclear Rabi oscillations are observed at a temperature of 120 K with an estimated decay time T2,Rabi ≈ 10 ms. TRIPLE resonance spectroscopy reveals an indirect J-coupling between 14N and 13C nuclei mediated by the distributed spin density of the optically polarized NV defect. The measured J-coupling of 5-6 Hz corresponds to an information transfer time of t ≈ 90 ms between nuclear qubits under a strong magnetic field (3.4 T).