Tip-Enhanced Molecular and Quantum Cavity Nano-Optics

在化学系化学测量和成像（CMI）计划的支持下，科罗拉多大学的Markus Raschke教授和他的团队正在开发一种称为尖端增强强耦合（TESC）的技术，作为测量和控制与光强耦合的单量子力学粒子特性的新方法。研究人员在扫描探针显微镜中的一个非常尖锐的金属尖端和一个镜面之间形成一个非常小的空腔，以将光捕获在包含单个粒子的空间区域中。通过原子精度调整腔的大小，使团队能够控制光与物质之间的相互作用，以形成由腔量子电动力学（cQED）描述的光-物质混合态。他们的方法克服了传统的腔体尺寸，被探测的粒子数量和测量温度要求的限制。这项工作提供了对强腔-发射极相互作用性质的基本理解，并实现了量子相干相互作用的室温控制，从而实现了新形式的单分子光谱学，量子传感和光化学控制。该项目利用了新开发的尖端增强强耦合（TESC）方法，该方法在扫描等离子体激元尖端和样品基底之间提供了以原子精度控制的皮腔模式体积。所得到的耦合强度甚至在室温下超过退相干，以单独寻址、动态调谐、主动控制和成像与光强耦合的单量子发射器。通过光致发光测量，TESC用于探测2D材料中的胶体量子点和固态缺陷作为模型量子发射体，以建立单发射体-单光子极限，并证明强耦合中的纠缠、光学非线性和光子阻塞。延伸到飞秒时间域，绝热飞秒纳米聚焦TESC测量这些发射器使用相干四波混频的竞争弛豫路径。结合固态发射器的变温TESC和低温尖端增强拉曼光谱（TERS）作为分子内振动能量重新分布的探针，工作导致对耦合的内部和外部电子和振动自由度的退相干的量子态分辨的基本理解。因此，这项工作有助于回答化学系统中电子波函数、声子和振动的工程量子相干性的基本极限问题--与任何形式的基于固态的量子技术有关的信息。为了实现其目标，该项目包括多样化的研究生和本科生培训，通过将cQED整合到课程课程中来发展劳动力，以及与行业合作，以加速量子信息应用的量子发射器开发。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, Professor Markus Raschke and his group at the University of Colorado are developing a technique called tip-enhanced strong coupling (TESC) as a new approach for measuring and controlling the properties of single quantum mechanical particles that are strongly coupled with light. The researchers form a very small cavity between a very sharp metallic tip in a scanning probe microscope and a mirror surface to trap light in a region of space containing the single particle. Tuning the cavity size with atomic precision allows the team to control the interaction between light and matter in order to form light-matter hybrid states that are described by cavity quantum electrodynamics (cQED). Their approach overcomes traditional limitations in cavity size, number of particles being probed, and temperature requirements for the measurements. The work provides a fundamental understanding of the properties of strong cavity-emitter interactions and enables room-temperature control of quantum coherent interactions, enabling new forms of single-molecule spectroscopy, quantum sensing, and control of photochemistry. This project takes advantage of the newly developed approach of tip-enhanced strong coupling (TESC), which provides a pico-cavity mode volume controlled with atomic precision between a scanning plasmonic tip and the sample substrate. The resulting coupling strength exceeds decoherence even at room temperature to individually address, dynamically tune, actively control, and image single quantum emitters that are strongly coupled with light. Through photoluminescence measurements, TESC is used to probe colloidal quantum dots and solid-state defects in 2D materials as model quantum emitters in order to establish the single emitter-single photon limit and to demonstrate entanglement, optical nonlinearities, and photon blockade in strong coupling. Extending into the femtosecond time domain, adiabatic femtosecond nano-focused TESC measures the competing relaxation pathways of these emitters using coherent four-wave mixing. In combination with variable temperature TESC of solid-state emitters, and low-temperature tip-enhanced Raman spectroscopy (TERS) as a probe of intramolecular vibrational energy redistribution, the work leads to a quantum-state-resolved fundamental understanding of decoherence to coupled internal and external electronic and vibrational degrees of freedom. The work thus helps answer the question of the fundamental limit of engineering quantum coherence of electronic wavefunctions, phonons, and vibrations in chemical systems – information pertinent to any form of solid-state-based quantum technologies. To achieve its goals, the project includes diverse graduate and undergraduate training, workforce development through cQED integration into the course curriculum, and industry collaborations to accelerate quantum emitter development for quantum information applications.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.