Spin Polarization and Transport at the Nanoscale

与钻石缺陷相关的量子自旋(氮空位色心)可以用来感应磁场，具有前所未有的灵敏度和空间分辨率。这些新型传感器可以在纳米尺度和环境条件下阐明材料和生物分子的结构和动力学。这些传感器成功的一个关键因素是了解它们的环境(由其他钻石自旋缺陷组成)，这些缺陷通常会破坏它们的性能。这个项目的重点不仅是了解氮空位中心与其自旋环境的相互作用，而且还将这些自旋转化为资源。这一目标将通过研究环境自旋特性和动力学以及开发控制技术来操纵和测量它们来实现。反过来，对自旋系统的更好理解和新的控制技术将产生用于传感和生物成像的改进的量子设备。此外，利用钻石中的氮空位中心在纳米尺度上探索自旋动力学的可能性，将促进人们对这种复杂的多体非平衡量子现象的认识，并对更广泛的学科产生影响，包括量子计算和核磁共振。该项目将在一个令人兴奋的多学科研究领域支持研究生研究人员的培训。这个研究项目将探索纳米尺度上的自旋极化的基本物理和潜在的应用，理论和实验之间的协同作用。该项目利用钻石中的氮空位(NV)中心作为种子和传感器，在周围的电子和核自旋环境中检测局部自旋极化。我们的目标是首先通过光学冷却NV中心及其与自旋浴的热接触来实现有效的偏振增强；其次，研究介观自旋环境中的后续动力学(偏振输运)。由于NV探测的高空间分辨率和新的材料工程技术，单自旋系统上的这些现象将能够在纳米尺度上进行研究。该计划的学术价值在于，通过实验和理论模型阐明了自旋扩散现象，研究了传统磁共振技术以前无法获得的尺度。自旋扩散是一个复杂的量子多体过程，它是磁共振实验中的退相干以及动态极化的基础。此外，通过使用工程材料，将研究如何通过电子自旋的准一维浴来促进远距离NV中心之间的相干自旋输运。这些研究将在不同的学科产生更广泛的影响，从量子计算和计量学，到通过动态核极化(DNP)进行蛋白质传感。钻石中的电子自旋可以用作自旋线，在位于NV中心的量子寄存器之间传输量子信息。极化的自旋浴可以通过NV中心来改进量子计量，通过创建纠缠态来实现更长的相干时间和海森堡限制的灵敏度。对自旋扩散的新见解-特别是在自旋扩散势垒-将导致改进的DNP策略，这是一种流行的核磁共振确定蛋白质结构的技术。超极化纳米钻石本身可以用作偏光剂，溶解在感兴趣的生物样品中以提高灵敏度。

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.