Quantum simulation using interacting spins in solids

纳米尺度的非侵入性磁成像是在原子尺度上理解有机和无机材料相互作用的关键。使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块状固态材料的研究。这项提议提出了开发和开发一种新型成像工具的途径和方法，这种成像工具是基于钻石中的单原子缺陷与位于钻石表面的电子自旋相耦合的。钻石中的氮空位中心(NV)是一种原子杂质，可以作为磁场、电场和温度的高度局域化传感器。NV电子自旋可以通过光学显微镜探测，不需要与传感设备直接电接触。从杂质中收集的光包含有关其微观量子状态的信息，这种状态会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，并在一秒的积分时间内仅检测到数百个核自旋。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，该传感器填补了成像技术中的一个重要空白，为纳米级软和固态系统中的探头结构和动力学提供了分辨率和灵敏度。然而，它的空间分辨率受到靠近钻石表面的NV中心的不稳定的限制：如果它离钻石表面更近几纳米，它的电荷状态就会改变，不再能够作为量子传感器。这阻止了它用于研究感兴趣的亚纳米分辨率的样品中的核自旋，因为在这些样品中会出现许多有趣的现象。该项目旨在开发一套新的基于钻石表面电子自旋团簇的磁性成像工具，目的是在亚纳米尺度上揭示迄今隐藏的物理现象。我们将利用钻石中单个NV中心和一小群顺磁钻石表面自旋之间的偶极耦合，为附近感兴趣的核自旋提供埃尺度的接近。我们将研究驻留在小分子体积液体中的核自旋，用于亚纳米尺度的传感，我们将探测原子完美的2D材料阵列中的核自旋。这种阵列为探索远程相互作用的二维多体系统中的纳米尺度自旋热化和局域化行为提供了一个平台。这提供了一个令人兴奋的机会，最终解决有关热化和二维多体定位的问题。有人预测，这种由相互作用的自旋组成的系统将显示出长时间的量子态，这与脆弱的量子系统暴露在与环境相互作用时通常观察到的快速热化相反。由于这类系统的复杂性，它们的行为无法通过传统的模拟来捕获，需要使用所谓的量子模拟器：模拟器本身就是量子系统，可以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。利用钻石表面自旋，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.