Quantum simulation using interacting spins in solids

纳米尺度的非侵入性磁成像是理解原子尺度上有机和无机材料相互作用的关键。利用磁共振技术检测电子和核自旋已经改变了结构生物学和大块固态材料的研究。该提案提出了开发和利用一种新型成像工具的路径和方法，该工具基于金刚石中的单原子缺陷与位于金刚石表面的电子自旋耦合。金刚石中的氮空位中心（NVs）是原子杂质，可以作为磁场和电场以及温度的高度局部化传感器。NV电子自旋可以通过光学显微镜探测，而不需要传感装置的直接电接触。从杂质收集的光包含有关其微观量子态的信息，这些信息将因其环境的任何变化而改变。例如，该系统允许将单个电子自旋定位到单个晶格位置，并且在一秒的积分时间内仅检测几百个核自旋。由于它是非侵入性的，并在环境条件下提供纳米级的空间分辨率，这种传感器填补了成像技术的重要空白，提供了分辨率和灵敏度的探针结构和动态在纳米级的软和固态系统。然而，它的空间分辨率受到靠近金刚石表面的NV中心的不稳定性的限制：如果它距离金刚石表面超过几纳米，它的电荷状态就会改变，它不再能够作为量子传感器。这阻止了它用于研究具有亚纳米分辨率的感兴趣样品中的核自旋，其中发生了许多有趣的现象。该项目旨在开发一套新的基于金刚石表面电子自旋团簇的磁成像工具，目的是揭示迄今为止隐藏的亚纳米级物理现象。我们将利用钻石中单个NV中心和一小群顺磁性钻石表面自旋之间的偶极耦合，以提供与附近感兴趣的核自旋的埃级接近。我们将研究原子核自旋驻留在亚纳米尺度传感液体的几个分子体积，我们将探测原子完美的二维材料阵列中的原子核自旋。这样的阵列提供了一个平台，探索纳米级的自旋热化和本地化行为在远程相互作用，二维，多体系统。这为最终解决二维热化和多体定位问题提供了一个令人兴奋的机会。据预测，这种由相互作用的自旋组成的系统将表现出长寿命的量子态，这与脆弱的量子系统暴露于与环境的相互作用时通常观察到的快速热化相反。由于这些系统的复杂性，它们的行为无法通过传统模拟来捕获，需要使用所谓的量子模拟器：模拟器本身就是量子系统，并捕获感兴趣的物理相互作用和动力学。在这里，我们将处于一个独特的位置，通过自旋控制和哈密顿工程技术来探索这个多体量子模拟器的相空间。利用金刚石表面自旋，我们的目标是揭示复杂自旋系统中的自旋热化动力学和多体效应。

Non-invasive magnetic imaging at the nanometre scale holds the key to understanding the interactions of organic and inorganic materials on the atomic scale. Sensing of electronic and nuclear spins using magnetic resonance techniques has already transformed structural biology and the study of bulk solid-state materials. This proposal sets out the path and methods to develop and exploit a new type of imaging tool based on single atomic defects in diamond coupled to electronic spins located right at the surface of diamond. Nitrogen vacancy centres (NVs) in diamond are atomic impurities that can serve as highly localised sensors for magnetic and electric fields, and temperature. The NV electronic spin can be probed through an optical microscope, not requiring direct electrical contacting of the sensing device. The light collected from the impurity contains information about its microscopic quantum state, which will be altered by any change in its environment. This system allows, for instance, the localization of individual electronic spins to single lattice sites and the detection of only a few hundred nuclear spins in one second of integration time. Because it is non-invasive and provides nanometre scale spatial resolution under ambient conditions, this sensor fills an important gap in imaging techniques, providing the resolution and sensitivity to probe structure and dynamics in soft and solid state systems on the nanometre scale. However, its spatial resolution is limited by the instability of the NV centre close to the surface of diamond: if it lies closer than a few nanometres to the diamond surface, its charge state changes and it is no longer able to act as a quantum sensor. This prevents its use for studying nuclear spins in samples of interest with sub-nanometre resolution, where many interesting phenomena occur. This project aims to develop a new set of magnetic imaging tools based on electronic spin clusters at the surface of diamond with the goal of revealing hitherto concealed physical phenomena at the sub-nanometre scale. We will exploit the dipolar coupling between a single NV centre in diamond and a small cluster of paramagnetic diamond surface spins to provide angstrom-scale proximity to nearby nuclear spins of interest. We will investigate nuclear spins residing in few-molecule volumes of liquids for sub-nm scale sensing and we will probe nuclear spins in the atomically perfect arrays of 2D materials. Such arrays provide a platform for exploring the nanoscale spin thermalisation and localisation behaviour in long-range interacting, two-dimensional, many-body systems. This presents an exciting opportunity to finally resolve questions regarding thermalisation and many-body localisation in two dimensions. It has been predicted that such systems composed of interacting spins will exhibit long-lived quantum states, contrary to the rapid thermalisation that is typically observed when fragile quantum systems are exposed to interactions with an environment. Due to the complexity of such systems, their behaviour cannot be captured by conventional simulations and require the use of so-called quantum simulators: simulators that are in themselves quantum systems and capture the physical interactions and dynamics of interest. Here, we will be in a unique position to explore the phase space of this many-body quantum simulator through spin control and Hamiltonian engineering techniques. Using the diamond surface spins, we aim to reveal spin thermalisation dynamics and many-body effects in complex spin systems.