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

普通观众摘要：当自由空间中的电子流通过有图案的表面时，就会产生光。在过去的一个世纪里，科学家和工程师使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被证明在许多应用中取得了成功，但这些光源背后的一些微观、量子物理仍然知之甚少。因此，我们还不知道这项技术的基本限制。在这个项目中，将揭示自由空间电子、图案化(或结构化)表面和光波之间相互作用的详细量子力学本质。具体地说，在这项工作中，单电子在真空中通过特殊设计的纳米级图案表面传输，将被用来产生单光子；并将研究由此产生的相互关联的所谓纠缠量子态。这项工作的发现可能会影响量子计算、量子通信和量子传感中的新兴应用，因为它提供了高效、低噪声和可调的单电子和单光子源，以及光子的独特量子态的源。除了这项工作的更广泛的科学影响，该计划还将有助于本科生和研究生研究人员的培训。此外，这项工作将包括为高中生提供暑期实习，并开发一系列由学生主导的研讨会，以提高受该计划支持的学生的指导、组织和领导技能。技术受众摘要：当低能自由电子(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区的电磁辐射。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，我们将探索自由电子、光和纳米结构材料之间相互作用的完整量子本质。具体地说，单电子将通过量身定制的纳米结构介导的相互作用产生单光子，并将通过实验探索电子和光子的量子相干性质。该项目将包括四个实验工作：(1)研究单光子与经过的自由电子的耦合，并将这种耦合用于发展预告性的单光子和单电子源；(2)通过使用多个相互作用结构产生Bell态来研究这种单光子-单电子耦合的量子相干性；(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，其中量子效率应该接近和超过1；以及(4)研究在引导电子束系统中的这种高效率区域中的多光子产生相互作用，以产生孤立的和纠缠的大光子数Fock态。这项工作将导致先进的自由电子和光子源，用于量子信息科学和技术，以及量子增强的自由电子和光学计量学。使用光子来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的无散粒噪声电子源成为可能。此外，这项工作中研究的量子相干电子-光子相互作用可能为紧凑地产生高度纠缠的光子态提供了一条可行的途径。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.