Quantum Superpositions of Free Electron Orbital Angular Momentum

电子是最微小的物质粒子，是最小的电荷火花，也是最小的磁铁。我们用这些小的、带电的、有磁性的物体为我们的城市供电，并用它们来存储、处理和交流信息。最近人们发现，在真空中自行运动的电子可以具有一个额外的、潜在有用的性质：轨道运动。单个自由电子也可以以这些轨道状态的组合存在，甚至可以同时显示出相反方向的轨道运动。这个项目的目的是通过在电子束中创建这样的混合轨道状态，如反向旋转的圆形轨道，来了解这些新的电子态的基本性质，并探索测量混合物中不同类型的轨道运动的新方法。要做到这一点，将使用通常用于纳米级成像的商业仪器(透射电子显微镜)。该仪器内部的电子束将通过精心设计的具有复杂图案的纳米级栅格。对光束的影响将使用栅格下游的探测器来测量。如果成功，这项研究将为操纵电子以及测量这种新的量子性质提供一种新的方法，为未来的量子电子学技术铺平道路，并提供探测物质轨道运动的新方法。像所有的量子力学波一样，单个自由电子的波函数可以自我扭曲，形成量子涡旋。这个项目的目的是利用纳米级的衍射全息图和其他新的电子光学设备，通过将自由电子放置在轨道态的相干叠加中来研究这些态的基本量子性质。在自由空间中，反旋转圆轨道叠加中的电子形成了一个电子干涉仪，可以用来探测电子波函数的几何相位、空间相干性和轨道角动量相关相移。除了准备轨道状态叠加的实验外，该项目还开发了非破坏性测量和分类的方法，可能会从散射电子中提供新的信息。

Electrons are the tiniest particle of matter, the smallest spark of charge, and smallest bit of magnet. We power our cities with these small, charged, magnetic objects, and use them to store, process, and communicate information. It was recently discovered that an electron moving by itself in vacuum can possess an additional, potentially useful, property: orbital motion. Individual free electrons can also exist in combinations of these orbital states, and can even be made to exhibit orbital motions in opposite directions at the same time. The purpose of this project is to understand the fundamental nature of these new electron states by creating such mixed orbital states in electron beams, such as counter-rotating circular orbits, and to investigate new ways to measure the different types of orbital motion present in a mixture. To do so, a commercial instrument that is typically used for nanoscale imaging (transmission electron microscope) will be used. The electron beam inside this instrument will be made to pass through nanoscale gratings carefully designed with complicated patterns. The effect on the beam will be measured using detectors downstream from the gratings. If successful, this research will provide a new way to manipulate the electron as well as measure this new quantum property, paving the way for future technologies in quantum electronics and providing new ways to probe orbital motion in matter. Like all quantum mechanical waves, the wave function of a single free electron can be twisted on itself to form a quantum vortex. The purpose of this project is to investigate the fundamental quantum nature of these states by placing free electrons in coherent superpositions of orbital states using nanoscale diffraction holograms and other new electron optical devices. Electrons in superpositions of counter-rotating circular orbits form an electron interferometer in free space, and it can be used to probe geometric phases, spatial coherence, and orbital angular momentum-dependent phase shifts of the electron wavefunction. In addition to experiments preparing superpositions of orbital states, the project also develops ways to nondestructively measure and sort them, potentially providing new information from scattered electrons.