Fig. 5: Coherent manipulation and sensing of electron and nuclear spins in a Cr[Na] single crystal.

A Rabi oscillation of spin qubits in Cr[Na] under different microwave driving frequencies (\({\omega }_{1}\)). B Rabi frequency (\({\omega }_{{Rabi}}\)) as a function of \({\omega }_{1}\), showing complex behavior due to the interplay between microwave driving, electron spin-spin self-interaction (S = 3/2), and electron-nuclear hyperfine interaction. C A Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence for nuclear spin sensing experiments. The dashed brackets represent the N repetition of \({\pi }_{Y}\) refocusing pulse. The nuclear magnetic resonance (NMR) dips are periodic with the resonant nuclear rotation frequency with the period \({\tau }_{I}\). D Coherence contrast (the CPGM echo/envelop decay) as a function of the CPMG inter-pulse delay (\({\tau }_{{CPMG}}\)) for the Cr[Na] single crystal with the magnetic field (B) aligned close to the [001] crystallographic direction, measured at 4 K (green) and 20 K (red). The gray data set is the 20 K results that are below the noise levels. E NMR frequency spectrum obtained by Fourier transformation of the CPMG coherence contrast shown in (D) demonstrating nuclear spin sensing at 4 and 20 K. The marked positions indicate NMR frequency of ¹³³Cs that interacts with Cr³⁺ spin qubit centers.