Microscopy and Spectroscopy of Topological Quantum Devices

项目目标：探索电子在纳米电子器件中的行为已经彻底改变了我们对量子系统的理解，并为广泛的固态量子技术奠定了基础。这个实验博士项目涉及探索一类新的量子器件，其电子特性由带结构拓扑控制。这些系统中的电子被迫沿着表面和边缘移动，从而避免了大量噪声和无序，这可能会提高量子比特和计量标准等量子设备的性能。该项目的主要目的是：1。探测拓扑超导体中的马约拉纳零模式：学术团队和微软等科技公司正在开发一种拓扑量子计算机，该计算机使用一种特殊类型的离域电子——马约拉纳零模式（MZM）——在超导体半导体纳米线的末端形成。迄今为止，MZMs仅被间接观察到，从未在显微镜下进行空间分辨。扫描栅极显微镜使用原子力显微镜的尖端作为可移动的局部栅极，将用于成像它们的位置作为磁场和栅极电压的函数。电路量子电动力学（cQED）将用于光谱检测嵌入超导量子比特的MZMs。这项研究的影响可能非常大，因为它将验证MZMs的空间位置，这是它们的定义特征之一。2. 成像磁掺杂拓扑绝缘体器件的拓扑间隙：我们将探索磁掺杂V-VI化合物，并拍摄电流在二维表面状态演变为一维边缘通道时的空间分布图像。捕获不同载流子密度和磁场下的图像应该可以准确地揭示这种转变是如何发生的，通过与地形进行比较，我们可以了解它是如何受到电离表面和块状杂质、边缘无序和晶体形态变化的影响的（参见https://magma.tmqs.lu/了解更多细节）。使用的技术、活动和设备：您将使用一系列低温扫描探针显微镜技术在纳米尺度上成像电子并验证这些拓扑特性。您还将学习电路量子电动力学、原子力显微镜、扫描电子显微镜、电子束光刻和低温输运测量等技术。米利开尔文在操作中扫描门显微镜、电输运测量和微波光谱将使用帝国理工学院的量子科学和设备设施进行。

Aims of the project: Probing how electrons behave in nanoelectronic devices has revolutionised our understanding of quantum systems and laid the foundations for a wide range of solid-state quantum technologies. This experimental PhD project involves probing a new class of quantum device whose electronic properties are governed by bandstructure topology. Electrons in these systems are forced to move along surfaces and edges where they avoid bulk noise and disorder, potentially improving the performance of quantum devices like qubits and metrological standards. The main aims of the project are:1. Detecting Majorana zero modes in topological superconductors: Academic teams and technology companies such as Microsoft are developing a topological quantum computer using a special type of delocalised electron - a Majorana zero mode (MZM) - that forms at the ends of superconductor-semiconductor nanowires. MZMs have so far only been observed indirectly and never spatially resolved microscopically. Scanning gate microscopy, which uses the tip of an atomic force microscopic as a mobile local gate electrode, will be used to image their position as a function of magnetic field and gate voltage. Circuit quantum electrodynamics (cQED) will be used to spectroscopically detect MZMs embedded in superconducting qubits. The impact of this study is potentially very high as it will verify the spatial location of MZMs, one of their defining features. 2. Imaging topological gaps in magnetically-doped topological insulator devices: We will explore magnetically-doped V-VI compounds and take images of the spatial distribution of currents as two-dimensional surface states evolve into the one-dimensional edge channels. Capturing images at different carrier density and magnetic field should reveal precisely how this transition takes place, and by comparing with topography we can understand how it is affected by ionised surface and bulk impurities, edge disorder, and variations in crystal morphology (see https://magma.tmqs.lu/ for more details).Techniques, activities, and equipment used: You will use a range of low temperature scanning probe microscopy techniques to image electrons at the nanoscale and verify these topological properties. You will also learn techniques such as circuit quantum electrodynamics, atomic force microscopy, scanning electron microscopy, electron-beam lithography and low-temperature transport measurements. Millikelvin in-operando scanning gate microscopy, electrical transport measurements, and microwave spectroscopy will be performed using the Quantum Science and Device Facility at Imperial.