Microscopy and Spectroscopy of Topological Quantum Devices

该项目的目标：探索电子在纳米电子设备中的行为方式，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。这个实验性的博士项目涉及探索一种新的量子器件，其电子性质由能带结构拓扑控制。这些系统中的电子被迫沿着表面和边缘移动，在那里它们避免了整体噪声和无序，这可能会提高量子设备的性能，如量子比特和计量标准。该项目的主要目标是：1.检测拓扑超导体中的Majorana零模：学术团队和技术公司(如微软)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--一种在超导体-半导体纳米线末端形成的Majorana零模(MZM)。到目前为止，MZM只被间接观察到，从未在空间上进行显微分辨。扫描门显微镜使用原子力显微镜的尖端作为移动的局部栅电极，将被用来成像作为磁场和栅电压的函数的它们的位置。电路量子电动力学(CQED)将被用于光谱检测嵌入在超导量子比特中的MZM。这项研究的影响可能非常大，因为它将验证MZM的空间位置，这是它们的定义特征之一。2.磁掺杂拓扑绝缘体器件的拓扑带隙成像：我们将探索磁性掺杂的V-VI化合物，并拍摄二维表面态演变为一维边缘沟道时电流的空间分布图像。在不同的载流子密度和磁场下捕获图像应该准确地揭示这种转变是如何发生的，通过与形貌的比较，我们可以了解它是如何受到电离表面和本体杂质、边缘无序和晶体形态变化的影响(有关更多详细信息，请参阅https://magma.tmqs.lu/)。所使用的技术、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级对电子进行成像并验证这些拓扑属性。你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、电子束光刻和低温传输测量等技术。将使用帝国理工学院的量子科学和设备设施进行Millikelvin in-Operando扫描门显微镜、电传输测量和微波光谱分析。

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.