A scanning quantum probe microscopy suite to boost the development of quantum circuits

噪声和退相干对固态量子计算的发展提出了严峻的挑战。通常，这种退相干和相关的量子比特参数漂移可以归因于原子尺度的材料缺陷，其中所知甚少，存在于用于构建量子电路的材料中。半导体行业（经典计算）在其早期面临着非常相似的材料挑战，但今天它显示出卓越的质量和产量。除了巨大的工程努力，这在很大程度上可以归因于新的纳米材料表征工具的出现。例如，原子力显微镜和扫描隧道显微镜的发展，以及广泛的衍生扫描探针显微镜（SPM）技术，使人们能够深入了解材料和完美的器件制造。量子计算现在已经成熟到一个水平，在它完全被利用之前，与材料相关的类似挑战仍然存在。因此，很明显，用于缺陷缓解的量子SPM（“扫描量子探针显微镜”，SQPM）工具将在未来几十年内推动量子计算（以及一般的量子技术）向前发展。然而，挑战（特别是在微波状态下运行的量子器件，如超导电路）是它们以前所未有的方式对缺陷敏感：缺陷具有非常低的能量尺度和低密度，使得相关缺陷无法通过传统技术检测。然而，这些微小的缺陷仍然对量子电路的相干性产生有害影响。到目前为止，现有的纳米级表征工具都无法像量子电路那样“看到材料缺陷”。该项目的目标是在开发SQPM工具方面迈出第一步，这些工具有朝一日将推动量子处理器材料的改进，从而彻底改变计算。这将通过建立在PI在量子机制中检测和控制单个材料缺陷和低温SPM仪器方面开发的现有能力来实现，以构建一个SQPM平台，该平台能够托管高相干量子电路，其中可以定位单个缺陷-将空间，结构和光谱缺陷属性直接与器件性能相关联。

Noise and decoherence poses a critical challenge for the development of quantum computing in the solid-state. Usually, this decoherence and associated qubit parameter drift can be attributed to atomic-scale material defects, of which little is known, present in the materials used to build quantum circuits. The semiconductor industry (classical computing) faced very similar material challenges in its early days, yet today it shows remarkable quality and yield. Apart from a tremendous engineering effort, much of this can be attributed to the emergence of new nanoscale material characterisation tools. For instance, the development of atomic force microscopy and scanning tunnelling microscopy, together with a broad range of derived scanning probe microscopy (SPM) techniques has allowed to gain in-depth knowledge of materials and perfect device fabrication. Quantum computing has now matured to a level where similar challenges related to materials remains before it can fully be exploited. It is thus clear that quantum SPM ('scanning quantum probe microscopy', SQPM) tools for defect mitigation will be essential to drive quantum computing (and quantum technologies in general) forward in the decades to come. However, the challenge (in particular with quantum devices operating in the microwave regime, such as superconducting circuits) is that they are sensitive to defects in a completely unprecedented way: the defects have very low energy scales and low densities, making the relevant defects impossible to detect by conventional techniques. Yet these otherwise minute defects still have detrimental effects on the coherence of quantum circuits. To date none of the existing nanoscale characterisation tools are capable of 'seeing the material defects' the way quantum circuits sees and suffers from them. This project aims to take the first fundamental steps in developing the SQPM tools that will one day drive the progress of refined materials for quantum processors posed to revolutionise computing. This will be achieved by building on existing capabilities developed by the PI in detection and control of individual material defects and cryogenic SPM instrumentation in the quantum regime, to construct a SQPM platform capable of hosting high coherence quantum circuits where individual defects can be located - correlating spatial, structural, and spectral defect properties directly with device performance.