Quantum spins associated with defects in diamond (Nitrogen-Vacancy color centers) can be used to sense magnetic fields with an unprecedented combination of sensitivity and spatial resolution. These novel sensors could elucidate the structure and dynamics of materials and biomolecules at the nano-scale and ambient conditions. A critical ingredient to the success of these sensors is the understanding of their environment (composed of other diamond spin defects) that usually spoil their properties. The focus of this project is not only to understand the interaction of Nitrogen-Vacancy centers with their spin environment, but also to turn these spins into a resource. This goal will be accomplished by studying the environmental spin properties and dynamics and by developing control techniques to manipulate and measuring them. In turns, a better understanding of the spin system and novel control techniques will yield improved quantum devices for sensing and bio-imaging. In addition, the ability to explore spin dynamics at the nano-scale, a possibility opened by the use of Nitrogen-Vacancy centers in diamond, will advance the knowledge of this complex, many-body non-equilibrium quantum phenomenon and have impact in broader disciplines, including quantum computation and MRI. This project will support the training of graduate student researchers in an exciting and multidisciplinary research field.
This research program will explore fundamental physics and potential applications of spin polarization at the nanoscale, with a synergistic interplay between theory and experiment. The project exploits the Nitrogen-Vacancy (NV) center in diamond as a seed and sensor of local spin polarization in the surrounding electronic and nuclear spin environment. The goals are to first achieve efficient polarization buildup via optical cooling of the NV center and its thermal contact with the spin bath; and second, to investigate the subsequent dynamics (polarization transport) in the mesoscopic spin environment. Thanks to high spatial resolution of NV detection and to novel material engineering techniques, these phenomena on single-spin systems, will be able to be studied at the nano-meter scale. The intellectual merit of the program lies in elucidating, via experiments and theoretical models, the phenomenon of spin diffusion, investigating scales not previously accessible to conventional magnetic resonance techniques. Spin diffusion is a complex quantum many-body process, which underlies, for example, decoherence in magnetic resonance experiments as well as dynamic polarization. In addition, by using engineered materials, how to promote coherent spin transport between distant NV centers, mediated by a quasi-one dimensional bath of electronic spins, will be studied. These studies will have a broader impact in different disciplines, from quantum computation and metrology, to protein sensing via dynamic nuclear polarization (DNP). Electronic spins in diamond can be used as spin wires to transfer quantum information between quantum registers located at the NV centers. A polarized spin bath can be used to improve quantum metrology via NV centers, by achieving longer coherence time and Heisenberg-limited sensitivity via the creation of an entangled state. Novel insight into spin diffusion -especially at the spin diffusion barrier- would lead to improved strategies for DNP, a popular technique in protein structure determination with NMR. Hyper-polarized nano-diamonds could themselves be used as polarizing agents, dissolved in bio-samples of interest for improved sensitivity.
