Coherent Electron Control

量子力学理论告诉我们电子、原子以及构成物质的所有粒子在微观尺度下的行为。经典力学理论告诉我们，桥梁、汽车以及构成我们日常世界中物体的所有部件在宏观尺度上是如何运动的。以一种平稳的方式将两者统一起来，得出微观和宏观尺度的一致理论，这是一个未解决的问题（“量子测量问题”），困扰了科学家大约一个世纪。为了解决这个问题，需要研究介于微观和宏观之间的中间尺度的物体。这就是“相干电子控制”项目的目标。电子被放置在墙壁中可控制数量的物质附近，因此两者如何相互作用的描述既不容易被量子力学描述，也不容易被经典力学描述。可用的最佳临时描述，称为退相干理论，可以用这种方法检验其极限。在实际应用方面，电子和壁之间的相互作用已经阻止了基于电子的敏感设备的发展，称为电子干涉仪。这些壁破坏了电子有用的量子力学特性。如果能够克服这种“退相干”，就可以制造出测量磁场微小变化的电子设备，从而可能有助于探测扭曲地球磁场的水下潜艇。纳米光栅被用作将电子束分成两部分的装置。这两部分被重新组合并表现出量子力学干涉。将掺杂硅、金和石墨烯等其他材料的壁以及超导材料放置在电子束附近，用于将电子束退相干，从而使量子力学干涉消失。四种不同的现有微观理论可以通过收集的实验数据进行测试；退相干理论是这四种理论不可分割的一部分。所获得的知识将用于控制和减少退相干，并应用于扩大现有电子干涉仪的尺寸。通过这种方式，它将试图构建世界上最大和最灵敏的电子干涉仪。本研究项目为研究生、本科生和高中生在自由电子量子光学的新研究领域提供了经验。

The theory of Quantum Mechanics tells us how electrons, atoms, and all particles that make up matter, behave at a microscopic scale. The theory of Classical Mechanics tells us how bridges, cars, and all parts that make up the objects in our everyday world, behave at a macroscopic scale. Unifying the two in a smooth way, to arrive at a consistent theory of both the microscopic and macroscopic scales is an unsolved problem (the "Quantum Measurement Problem") that has perplexed scientists for about one century. To solve this problem, objects at an intermediate scale, in between the microscopic and macroscopic, need to be studied. This is what the project: "Coherent Electron Control" is aiming to do. Electrons are placed close to a controllable amount of material in a wall, so that the description of how the two interact is neither easily described by Quantum Mechanics, nor Classical Mechanics. The best provisional description available, which is called decoherence theory, can be tested to its limits in this way. On the practical side, the interaction between electrons and walls has stopped the development of sensitive devices based on electrons, called electron interferometers. The walls destroy the useful quantum mechanical properties of the electrons. If this "decoherence" can be overcome, electron devices can be constructed that measure small changes in magnetic fields, and may thus assist, for example, in the detection of submerged submarines that distort the Earth's magnetic field. Nanofabricated gratings are used as devices that split electron beams into two parts. These two parts are recombined and show quantum mechanical interference. Walls of doped silicon, gold, and other materials such as graphene and superconductive materials will be placed close to the electron beams used to decohere the electron beams, which causes the quantum mechanical interference to disappear. Four different existing microscopic theories can be tested by the experimental data that will be collected; decoherence theory is an integral part of all four. The knowledge gained will be used to control and reduce the decoherence and be applied to enlarge the size of existing electron interferometers. In this way it will be attempted to construct the largest and most sensitive electron interferometer in the world. This research project provides experience to graduate students, undergraduate students and high school students in the new research area of free electron quantum optics.