QLC: EAGER: Collaborative Research: Developing Experiment and Theory for Entangled Photon Spectroscopy

仅供草稿！该研究项目关注的是理解光与分子相互作用时产生的量子现象。光可以被认为涉及被称为光子的能量束，这个项目的重点是分子几乎同时吸收两个光子。通常情况下，光子是相互独立的，但存在一种量子效应，即两个光子相互纠缠，两个光子的吸收是强相关的。当这种情况发生时，两个光子的吸收速度可以提高许多个数量级，这在从电子设备到化学传感的各种应用中都很有意义。然而，人们对这一过程知之甚少，已经进行的少数几个实验显示，类似分子的行为相互矛盾。因此，这项研究包括测量和计算模型，以研究纠缠光子的吸收。从事这一项目的学生和博士后正在接受新的实验和理论技术方面的培训，这些技术可能会在基于这些独特的量子效应的新技术开发过程中发挥作用。此外，皮？S正在积极开展与他们的研究相关的推广项目，涉及到广泛的社会阶层。在这个项目中，量子光学实验方法和量子电子计算方法正在被用于研究通过纠缠双光子吸收(ETPA)可获得的有机分子的新性质。实验和理论都利用了自发参量下转换过程中产生的光子的量子纠缠，以及随后分子中电子态的激发。理论上预测，ETPA现象将表现出有趣的非经典效应，如吸收速率与入射光子通量的线性关系，而不是二次关系。在之前的工作中，派？S之一的古德森在他的实验室里开发了实验方法，使测量各种分子的ETPA截面成为可能，并且确实观察到了对光子通量的线性依赖。在这项早期工作中，令人惊讶的是，一些分子显示出显着的ETPA横截面，而其他名义上相似的分子则没有显示出可观察到的ETPA。更进一步，在这项工作中，理论和实验的目的是了解参与ETPA的中间态。理论研究包括计算耦合激发态的跃迁矩，这是电子结构理论通常缺少的一种能力。然而，该项目利用了另一个PI，Schatz的一种新的TDDFT方法来计算能量和过渡矩，并由此计算ETPA横截面。结果正在与使用一种新设备的泵浦-探测纠缠时间分辨测量进行比较，目的是找出中间态在ETPA中的作用。该理论的成功实施将导致对尚未研究的分子进行有趣的ETPA行为的预测，这将刺激进一步的实验工作，从而发现新的分子性质。该项目还涉及培养研究生和博士后，使他们能够发展自己的职业生涯，探索量子世界尚未考虑的方向。此外，PIS有积极的外展计划，在这些计划中，本提案中描述的研究在从量子力学研究生课程到面向公众的演讲的各个层面上呈现。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。

DRAFT ONLY!The research project is concerned with understanding quantum phenomena that are arise when light interacts with molecules. Light can be thought of as involving bundles of energy known as photons, and the focus of this project involves the near-simultaneous absorption of two photons by molecules. The photons normally act independently, but there is a quantum effect in which two photons become entangled, and absorption of the two photons is strongly correlated. When this happens, the rate of absorption of two photons can be enhanced by many orders of magnitude, which is of interest in applications that range from electronic devices to chemical sensing. However the process is poorly understood, with the few experiments that have been done showing conflicting behavior for similar molecules. The research therefore includes both measurements and computational modeling to study the absorption of entangled photons. Students and postdocs who work on this project are being trained in new experimental and theoretical techniques that are likely to play a role as new technologies are developed based on these unique quantum effects. In addition, the PI?s are engaging in active outreach programs related to their research that touches on broad segments of society.In this project a quantum optical experimental approach and a quantum electronic computational approach are being applied to investigate new properties of organic molecules that are accessible through entangled two-photon absorption (ETPA). Both experiment and theory take advantage of the quantum entanglement of photons created by the process of spontaneous parametric down conversion and the subsequent excitation of electronic states in molecules. The phenomenon of ETPA has been theoretically predicted to exhibit interesting non-classical effects such as linear rather than quadratic dependence of absorption rate on incident photon flux. In prior work, one of the PI?s, Goodson, developed experimental methods in his lab which make it possible to measure ETPA cross sections for a wide variety of molecules, and indeed the linear dependence on photon flux was observed. A surprise in this earlier work is that some molecules show significant ETPA cross sections while other nominally similar molecules show no observable ETPA. To go further, in this work, theory and experimentsare aimed at understanding intermediate states that participate in ETPA. The theory studies involve calculating transition moments that couple excited states, which is an ability that is generally missing from electronic structure theories. However the project takes advantage of a new TDDFT approach from the other PI, Schatz, for calculating energies and transition moments, and from this to evaluate ETPA cross sections. The results are being compared with pump-probe entangled time-resolved measurements using a new apparatus, with the goal of sorting out the role of intermediate states in ETPA. Successful implementation of the theory should lead to predictions of interesting ETPA behavior for molecules not yet studied, and this will stimulate further experimental work leading to the discovery of new molecular properties. The project is also concerned with training graduate students and postdocs, and enabling them to develop careers of their own that explore directions of the quantum world that haven?t yet been considered. In addition, the PIs have active outreach programs where the research described in this proposal is presented at levels that range from graduate courses in quantum mechanics to talks to the general public.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.