Collaborative Research: Quantum-Coherent Interactions between Free and Guided Electrons and Photons

一般观众摘要：当一束电子在自由空间中经过一个有图案的表面时，就会产生光。在过去的一个世纪里，科学家和工程师们利用这一过程为从卫星通信到微波炉的各种应用提供动力。尽管这些电子驱动的光源已经在许多应用中被证明是成功的，但这些光源背后的一些微观量子物理学仍然知之甚少。因此，我们还不知道这种技术的基本限制。在这个项目中，自由空间电子、图案（或结构）表面和光波之间相互作用的详细量子力学性质将被揭示。具体来说，在这项工作中，单电子在真空中穿行，经过专门设计的纳米长度尺度的表面，将被用来产生单光子；由此产生的相互连接的，所谓的纠缠态，量子态将被研究。这项工作的发现可以通过提供高效、低噪声和可调谐的单电子和单光子源，以及光子的独特量子态源，影响量子计算、量子通信和量子传感等新兴应用。除了这项工作的更广泛的科学影响之外，该计划还将有助于培养本科生和研究生研究人员。此外，这项工作还将包括为高中生提供暑期实习机会，并开发一个由学生主导的系列研讨会，以提高该项目支持的学生的指导、组织和领导技能。摘要：当低能量的自由电子（几到几十keV）与纳米结构材料相互作用时，可以产生从太赫兹到可见域的电磁辐射。最近，研究人员研究了自由电子在纳米级物体和表面附近与经典光相互作用后的量子相干性质。在这个项目中，将探索自由电子、光和纳米结构材料之间相互作用的完整量子性质。具体来说，单个电子将通过定制的纳米结构介导的相互作用产生单个光子，并且电子和光子的量子相干特性将通过实验进行探测。该项目将包括四项实验工作：(1)研究单光子与通过的自由电子的耦合，并利用这种耦合开发预示的单光子和单电子源；(2)利用多重相互作用结构对单光子-单电子耦合的量子相干性进行了贝尔态生成研究；(3)通过纳米结构电子束波导扩展量子相干电子-光子相互作用，使量子效率接近和超过单位；(4)在引导电子束系统中，在这种高效率的状态下，研究多光子产生相互作用，以产生孤立和纠缠的大光子数Fock态集。这项工作将为量子信息科学和技术以及量子增强自由电子和光学计量提供先进的自由电子和光子源。使用光子预示电子到达的能力将使低剂量电子显微镜、改进的电子束光刻和量子增强的自由电子计量学的无射噪声电子源成为可能。此外，本研究中所研究的量子相干电子-光子相互作用可能为高纠缠光子态的紧凑产生提供了一条可行的途径。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

General audience abstract:When a stream of electrons in free space passes over a patterned surface, light is produced. Over the past century, scientists and engineers have used this process to power applications ranging from satellite communications to microwave ovens. Although these electron-driven light sources have proven successful in numerous applications, some of the microscopic, quantum physics underlying these sources has remained poorly understood. As a result, we do not yet know the fundamental limits of this technique. In this project, the detailed, quantum-mechanical nature of the interactions between free-space electrons, patterned (or structured) surfaces, and light waves will be uncovered. Specifically, in this work, single electrons, traveling through vacuum over specially designed surfaces patterned at the nanometer length scale, will be used to generate single photons; and the resulting interconnected, so-called entangled, quantum states will be studied. The findings from this work could impact emerging applications in quantum computing, quantum communication, and quantum sensing by providing efficient, low-noise, and tunable sources of single electrons and single photons, as well as sources of unique quantum states of photons. Beyond the broader scientific impact of this work, this program will also contribute to the training of undergraduate and graduate researchers. Additionally, the effort will include summer internships for high-school students and develop a student-led seminar series that will improve the mentoring, organizational, and leadership skills of the students supported by this program.Technical audience abstract:When low-energy free electrons (few to tens of keV) interact with nanostructured materials, electromagnetic radiation, from the terahertz to the visible domain, can be produced. Recently, researchers have investigated the quantum-coherent nature of free electrons after interacting with classical light in the vicinity of nanoscale objects and surfaces. In this project the complete quantum nature of the interactions between free electrons, light, and nanostructured materials will be explored. Specifically single electrons will generate single photons via an interaction mediated by tailormade nanostructures, and the quantum-coherent properties of the electrons and photons will be experimentally probed. The project will consist of four experimental efforts: (1) The study of the coupling of single photons to a passing free electron and the use of this coupling for the development of heralded single-photon and single-electron sources; (2) The investigation of the quantum coherence of this single-photon-single-electron coupling by using multiple interaction structures for the generation of Bell states; (3) The extension of the quantum-coherent electron-photon interaction via nanostructured electron-beam waveguides in which quantum efficiencies approaching and exceeding unity should be achievable; and (4) The study of multiple photon-generation interactions in this high-efficiency regime within guided electron beam systems to generate both isolated and entangled sets of large-photon-number Fock states. This work will lead to advanced free-electron and photon sources for quantum information science and technology and quantum-enhanced free-electron and optical metrology. The ability to use photons to herald electron arrival would enable shot-noise-free electron sources for low-dose electron microscopy, improved electron beam lithography, and quantum-enhanced free-electron metrology. Furthermore, the quantum-coherent electron-photon interactions studied in this work may additionally provide a viable path for the compact generation of highly-entangled photon states.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.