'Double-slit' and multiple-path Interference studies from Rb excited and ionized by high-resolution laser radiation.

高分辨率激光辐射激发和电离铷的“双缝”和多路干涉研究。

• 批准号: EP/V027689/1
• 负责人: Andrew Murray
• 金额: $ 72.36万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV027689%2F1
• 关键词: Double; slit; multiple; path; Interference

The double-slit experiment using electrons to produce interference at a detector was voted as one of the 5 'most beautiful experiments in physics' by Physics World readers in 2002. Recent experiments in 2013 demonstrated that SINGLE electrons that were detected before the next electron was emitted also produce an interference pattern when the signal builds up over time. This convincingly shows individual electrons have both wave-like & particle-like character, as predicted by Richard Feynman in the early 1960's. Feynman thought such experiments would never be done, however advances in technology since then have now made this possible. The interference pattern arises since we do not know which slit the electron passes through. We assign a wavefunction to the electron, & the slits then define 2 possible pathways for the wave to travel from source to detector. The wavefronts beyond the slits then recombine at the detector, & the square of their sum gives the probability an electron is detected. If the peak of one wave meets the trough of another, the waves cancel & there is zero probability an electron will be detected at that position. By contrast, if two peaks or two troughs arrive at a point, there is then maximum probability an electron will be detected. An interference pattern is hence produced across the detector, which depends on how the waves recombine at any given point.In Manchester we recently invented a new type of 'double-slit' experiment in a single atom, where the 'slits' are replaced by atomic states 1 & 2 excited by lasers. The laser beam that excites state 1 also ionizes state 2, whereas the laser exciting state 2 ionizes state 1. There are then 2 pathways to ionization, & we do not know which was taken to produce the detected photoelectron. We again have to add the wavefunctions from each path to determine the outcome, leading to interference. The states (slits) can be turned on or off (effectively opening or closing individual slits) by selectively tuning & detuning the lasers & this allows us to determine the interference pattern.In the new experiments to be carried out in this proposal we will explore this process in much greater detail, by selecting different excited states & by using different laser polarizations. Our collaborators in Germany theoretically predict this will produce large changes to the ensuing pattern. A further prediction we will explore is that injection of a third laser beam can selectively control the interference. This new idea has no analogy in a conventional double-slit experiment & may find application in other areas where wavefunctions must be manipulated (e.g. quantum computing).There is no reason why these processes must be confined to single atoms & the second facet of this work will explore how laser excitation & ionization can be applied to arrays of atoms. We will first cool the atoms to close to absolute zero in a magneto-optical trap, before creating a periodic array of excited atoms using a standing-wave laser. The atoms will then be ionized by a second laser, set so that the de Broglie wavelength of the emerging photoelectrons is comparable in size to the dimensions of the array. Interference will once again occur, however now the summation is for waves from ALL sites from which the photoelectrons are born. The resulting yield then depends on both the individual atoms, as well as their position in the array. This is expected to be similar to the effect a diffraction grating has on light, however now the waves are for electrons rather than photons. By altering the properties of the lasers we can 'shape' the grating in different ways, which will change the electron distribution that is produced. Initial models from our collaborators support these ideas & experiments are needed to test & refine the models. This work could find application in electron diffraction studies of surfaces & for controlling the injection of electrons into particle accelerators.

2002年，利用电子在探测器上产生干涉的双缝实验被《物理世界》的读者评选为“物理学中最美丽的5个实验”之一。2013年的实验表明，在下一个电子发射之前检测到的单个电子也会在信号随着时间的推移而积累时产生干涉图样。这令人信服地表明，单个电子既有波的性质，又有粒子的性质，正如理查德·费曼在20世纪60年代早期所预测的那样。费曼认为这样的实验永远不会完成，然而从那时起，技术的进步使这成为可能。干涉图样的出现是因为我们不知道电子通过哪个狭缝。我们给电子分配一个波函数，然后狭缝定义了波从源到检测器的两条可能的路径。然后，狭缝之外的波前在探测器处重新组合，它们和的平方给出了电子被探测到的概率。如果一个波的波峰与另一个波的波谷相遇，两个波就会相互抵消&在那个位置检测到电子的概率为零。相比之下，如果两个波峰或两个波谷到达一个点，那么检测到电子的概率最大。在曼彻斯特，我们最近发明了一种新型的单原子“双缝”实验，其中“缝”被激光激发的原子态1和2所取代。激发态1的激光束也电离态2，而激光激发态2电离态1。然后有两条电离途径，我们不知道哪一条产生了检测到的光电子。我们再次必须将每条路径的波函数相加，以确定结果，从而导致干涉。通过选择性地调谐和失谐激光，可以打开或关闭状态（狭缝）（有效地打开或关闭单个狭缝），这使我们能够确定干涉图样。在本提案中进行的新实验中，我们将通过选择不同的激发态和使用不同的激光偏振来更详细地探索这一过程。我们在德国的合作者理论上预测，这将对随后的模式产生巨大的变化。我们将探索的进一步预测是，注入第三束激光可以选择性地控制干涉。这个新的想法在传统的双缝实验中没有类似的东西，可能会在波函数必须被操纵的其他领域（例如量子计算）中找到应用。没有理由这些过程必须局限于单个原子，这项工作的第二个方面将探索如何将激光激发和电离应用于原子阵列。我们将首先在磁光阱中将原子冷却到接近绝对零度，然后使用驻波激光器创建激发原子的周期性阵列。然后，原子将被第二束激光电离，激光的设置要使出现的光电子的布罗意波长与阵列的尺寸相当。干涉将再次发生，但是现在求和是针对来自光电子产生的所有位置的波。因此，最终的产量取决于单个原子以及它们在阵列中的位置。这被认为与衍射光栅对光的影响类似，但现在的波是电子而不是光子。通过改变激光器的特性，我们可以以不同的方式“塑造”光栅，这将改变产生的电子分布。我们合作者的初始模型支持这些想法，需要实验来测试和完善模型。这项工作可以在表面的电子衍射研究中找到应用&用于控制电子注入粒子加速器。

项目成果

Laser-atom interaction simulator derived from quantum electrodynamics

基于量子电动力学的激光-原子相互作用模拟器

• DOI: 10.1103/physreva.105.053117
• 发表时间: 2022
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Patel M

Measurements of the Kr (e, 2e) differential cross section in the perpendicular plane, from 2 eV to 120 eV above the ionization threshold

垂直平面中 Kr (e, 2e) 微分截面的测量，电离阈值以上 2 eV 至 120 eV

• DOI: 10.48550/arxiv.2304.00956
• 发表时间: 2023
• 作者: Murray A

Measurements of the Kr ( e , 2 e ) differential cross section in the perpendicular plane from 2 to 120 eV above the ionization threshold

在高于电离阈值 2 至 120 eV 的垂直平面内测量 Kr ( e , 2 e ) 微分截面

• DOI: 10.1103/physreva.107.062807
• 发表时间: 2023
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Murray A

An undergraduate physics experiment to measure the frequency-dependent impedance of inductors using an Anderson bridge

使用安德森电桥测量电感器频率相关阻抗的本科物理实验

• DOI: 10.1119/5.0148114
• 发表时间: 2023
• 期刊: American Journal of Physics
• 影响因子: 0.9
• 作者: Murray A

A low-cost and reliable laser shutter interlock using a software-command interface

使用软件命令接口的低成本且可靠的激光快门联锁

• DOI: 10.1088/1361-6501/ac8ca7
• 发表时间: 2022
• 期刊: Measurement Science and Technology
• 影响因子: 2.4
• 作者: Rogers J