Multifrequency spin resonance in diamond

Magnetic resonance techniques provide a powerful tool for controlling spin systems, with applications ranging from quantum information processing to medical imaging. Nevertheless, the behavior of a spin system under strong excitation remains a rich dynamical problem. In this paper, we examine spin resonance of the nitrogen-vacancy center in diamond under conditions outside the regime where the usual rotating wave approximation applies, focusing on effects of multifrequency excitation and excitation with orientation parallel to the spin quantization axis. Strong-field phenomena such as multiphoton transitions and coherent destruction of tunneling are observed in the spectra and analyzed via numerical and analytic theory. In addition to illustrating the response of a spin system to strong multifrequency excitation, these observations may inform techniques for manipulating electron-nuclear spin quantum registers

Charge State Dynamics During Excitation and Depletion of the Nitrogen Vacancy Center in Diamond

The charge state dynamics of the nitrogen-vacancy (NV) center in diamond play a key role in a wide range of applications, yet remain imperfectly understood. Using single ps-pulses and pulse pairs, we quantitatively investigate the charge dynamics associated with excitation and fluorescence depletion of a single NV center. Our pulsed excitation approach permits significant modeling simplifications, and allows us to extract relative rates of excitation, stimulated emission, ionization, and recombination under 531 nm and 766 nm illumination. By varying the duration between paired pulses, we can also investigate ionization and recombination out of metastable states. Our results are directly applicable to experiments employing stimulated emission-depletion imaging, and can be used to predict optimal operating regimes where excitation and stimulated emission are maximized relative to charge-state-switching processes

Comparing continuous and pulsed nitrogen-vacancy DC magnetometry in the optical-power-limited regime

Ensembles of nitrogen-vacancy (NV) center spins in diamond offer a robust, precise and accurate magnetic sensor. As their applications move beyond the laboratory, practical considerations including size, complexity, and power consumption become important. Here, we compare two commonly-employed NV magnetometry techniques -- continuous-wave (CW) vs pulsed magnetic resonance -- in a scenario limited by total available optical power. We develop a consistent theoretical model for the magnetic sensitivity of each protocol that incorporates NV photophysics - in particular, including the incomplete spin polarization associated with limited optical power; after comparing the models' behaviour to experiments, we use them to predict the relative DC sensitivity of CW versus pulsed operation for an optical-power-limited, shot-noise-limited NV ensemble magnetometer. We find a $\sim 2-3 \times$ gain in sensitivity for pulsed operation, which is significantly smaller than seen in power-unlimited, single-NV experiments. Our results provide a resource for practical sensor development, informing protocol choice and identifying optimal operation regimes when optical power is constrained.Comment: Accepted version (JOSA B). Copyright 2023 Optica Publishing Group. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibite

Probing a spin transfer controlled magnetic nanowire with a single nitrogen-vacancy spin in bulk diamond

The point-like nature and exquisite magnetic field sensitivity of the nitrogen vacancy (NV) center in diamond can provide information about the inner workings of magnetic nanocircuits in complement with traditional transport techniques. Here we use a single NV in bulk diamond to probe the stray field of a ferromagnetic nanowire controlled by spin transfer (ST) torques. We first report an unambiguous measurement of ST tuned, parametrically driven, large-amplitude magnetic oscillations. At the same time, we demonstrate that such magnetic oscillations alone can directly drive NV spin transitions, providing a potential new means of control. Finally, we use the NV as a local noise thermometer, observing strong ST damping of the stray field noise, consistent with magnetic cooling from room temperature to $\sim$150 K.Comment: 6 pages, 5 figures, plus supplementary informatio

Capacitive coupling of atomic systems to mesoscopic conductors

We describe a technique that enables a strong, coherent coupling between isolated neutral atoms and mesoscopic conductors. The coupling is achieved by exciting atoms trapped above the surface of a superconducting transmission line into Rydberg states with large electric dipole moments, that induce voltage fluctuations in the transmission line. Using a mechanism analogous to cavity quantum electrodynamics an atomic state can be transferred to a long-lived mode of the fluctuating voltage, atoms separated by millimeters can be entangled, or the quantum state of a solid state device can be mapped onto atomic or photonic states.Comment: 4 pages, including one figure. v2: Improved discussion of surface effect