Coherent quantum control of nitrogen vacancy spin with nanoscale magnets

Coherent control of the nitrogen-vacancy (NV) center in diamond is commonly achieved by microwave fields from conventional antennas, which suffer from scalability and thermal noise. Their spatially extended field profiles also limit their specificity in driving one NV spin without affecting other NV spins. Here, we investigate quantum control of a single NV center with microwave fields generated from a nanoscale magnet that is proximal to the NV center. Our results show nanoscale coherent control with high contrast Rabi oscillations using nearfield microwaves from shape anisotropic nanomagnets of lateral dimensions down to 200 $\mathrm{nm}$ , driven by surface acoustic wave (SAW) excitation. Furthermore, we show that varying the acoustic power driving such nanomagnets can achieve control over Rabi frequency. We also report spin-spin relaxation time ( $T_2$ ) of the NV center, measured up to 3.48 $\pm$ 0.01 μs using microwave pulses generated by such nanomagnets. The use of the nanoscale magnets to implement highly localized coherent quantum control can replace thermally noisy microwave circuits and demonstrate a path to scalable quantum computing and sensing with NV-defects in diamond and other spin qubits.