Quantum dynamics methods for fluctuating systems in quantum environments: Development and application

纽约城市大学皇后学院的Seogjoo J.Jang因开发和应用量子环境中涨落系统的量子动力学方法而获得化学系化学理论、模型和计算方法项目颁发的奖项支持。例如，想象一种分子物质，比如糖，溶解在一杯水中。人们可以将糖分子中的电子视为量子系统，将糖分子中原子的振动视为量子环境。这些波动是由溶剂分子的运动引起的。由于量子力学的反直觉性质，如果不进行详细的计算，就很难预测或理解量子系统的行为。然而，即使在量子力学理论建立近一个世纪后，除了简单的模型和系统之外，可靠的量子动力学计算仍然很难解决。在他们早期计算研究的基础上，张教授和他的同事们正在建立适用于现实环境中非常大的系统的系统计算方法。准确描述这类量子系统的动力学行为对于设计新型的能量转换、成像和信息处理设备具有重要意义。这些方法的应用可以阐明在嘈杂环境中仍然重要的量子效应，并有助于开发新型量子设备。张教授正在撰写一本关于分子激子的书，这本书对太阳能转换和成像非常重要，他还在撰写一篇关于量子动力学方法的评论文章。他还致力于组织前沿主题的会议，并正在开发实验和计算相结合的新型本科课程。张教授的团队正在开发和应用理论和计算方法，用于研究与量子环境相互作用时受一般时间相关涨落影响的量子系统的动力学计算。准确地描述这两个复杂因素的相互作用对于研究复杂分子环境中的长程能量和电荷转移过程具有重要意义，也是量子热力学、信息处理和电导研究的中心问题之一。一方面，这一理论是通过主方程方法来追求的，通过将极化子变换或模粗粒化与系统的高阶展开相结合。另一方面，将基于路径积分的理论和仿真方法推广到波动系统。然后将这些方法应用于捕光络合物和纳米管中的离域激子的动力学，以及动态分子环境中的质子或质子耦合的电子转移反应。这项研究的结果可以阐明复杂环境中离域激子的时空动力学，并可以为量子环境效应与质子和松散电子动力学中随时间变化的涨落之间的相互作用提供关键见解。张教授正在撰写一本关于分子激子动力学的书，以及一篇关于量子大师和福克-普朗克方程的综合综述文章。他继续组织关于激子、量子信息、机器学习和化学传感等热门问题的会议和研讨会，并正在设计能够整合实验和计算/建模的新的小组化学课程。该奖项反映了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。

Seogjoo J. Jang of Queens College, City University of New York, is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry for developing and applying quantum dynamics methods for fluctuating systems in quantum environments. For example, think of a molecular substance, like sugar, dissolved in a glass of water. One could think of the electrons in the sugar molecule as the quantum system and the vibrations of the atoms in the sugar molecule as the quantum environment. The fluctuations are caused by the motions of the solvent molecules. Because of the counter-intuitive nature of quantum mechanics, it can be difficult to predict or understand the behavior of quantum systems without elaborate calculations. However, even after almost a century since the theory of quantum mechanics was founded, reliable quantum dynamics calculations beyond simple models and systems remain notoriously difficult to solve. Building on their earlier computational research, Professor Jang and coworkers are establishing systematic computational approaches appropriate for very large systems in realistic environments. Accurate descriptions of the dynamic behaviors of such quantum systems has significant implications for designing novel energy conversions, imaging, and information processing devices. Applications of these methods can elucidate quantum effects that remain important in noisy environments and can help develop new kinds of novel quantum devices. Professor Jang is working on a book on molecular excitons, which are important for solar energy conversion and imaging, and a review article on quantum dynamics methods. He is also dedicated to organizing conferences on cutting edge topics, and is developing new types of undergraduate level classes integrating experiments and computation.Professor Jang's group is developing and applying theories and computational methods for the dynamics calculation of quantum systems subject to general time dependent fluctuations while interacting with quantum environments. Accurate descriptions of the interplay of these two complicating factors has significant implications for long-range energy and charge transfer processes in complex molecular environments, and is one of central issues in quantum thermodynamics, information processing, and conductance. On one hand, this theory is pursued through master equation approaches, by combining the polaron transformation or modular coarse-graining with systematic higher order expansions. On the other hand, path-integral based theories and simulation methods are generalized for fluctuating systems. These methods are then applied and tested for the dynamics of delocalized excitons in light harvesting complexes and nanotubes, and for proton or proton-coupled electron transfer reactions in dynamic molecular environments. Outcomes of this research can elucidate spatio-temporal dynamics of delocalized excitons in complex environments and can provide key insights into the interplay between the effects of quantum environments and time dependent fluctuations in the dynamics of protons and loose electrons Professor Jang is working on a book on the dynamics of molecular excitons and a comprehensive review article on quantum master and Fokker-Planck equations. He continues organizing conferences and workshops on topical issues such as excitons, quantum information, machine learning, and chemical sensing, and is also designing new small group chemistry courses that can integrate experiments and computation/modeling.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.