Mixed Quantum-Classical Dynamics of Quantum Energy Transfer Processes

从预测新现象到解释实验结果，分子动力学已经成为实验学家和理论家不可或缺的工具。采用物质的经典描述，人们可以对包含大量粒子的系统进行分子动力学模拟。然而，当粒子表现出波动性质时，经典的描述不再有效。量子分子动力学方法是可用的，但它们仅限于非常小的系统，因为它们的计算成本随粒子数量呈指数级增长。为了处理更大的系统，可以求助于混合量子经典方法，其处理系统的关键部分（即，子系统）以量子力学的方式而其余部分（即，洗澡（classical）多年来，已经开发了许多混合量子-经典动力学算法。其中最精确的算法性能非常好，但计算成本很高。最近，我们开发了一种方法，表现出计算成本和准确性之间的有利平衡。然而，在其目前的制定，这种方法是有限的系统，其势能可以表示为多项式形式，其子系统迅速失去记忆的浴动态。因此，我们的研究计划的第一部分将集中在推进这种方法沿着几个方向，使之更普遍，准确，有效。该结果有望成为模拟量子-经典混合系统动力学的一个非常有力的工具。 我们的研究计划的第二部分将侧重于将我们的混合量子经典方法的当前和未来配方应用于具有基础和技术重要性的量子能量转移/存储过程。具体来说，我们将探索分子电子学和纳米声学应用中涉及的量子传热过程，以及量子电池中的能量存储。我们的目标是深入了解影响各种分子系统中热传递速率/机制的因素，并提出量子电池的实用设计。这项研究所获得的知识将最终有助于开发用于量子技术的强大，高效和可控的纳米级器件。

From predicting new phenomena to interpreting experimental findings, molecular dynamics has become an indispensable tool for both experimentalists and theorists. Adopting a classical description of matter, one can perform molecular dynamics simulations of systems containing very large numbers of particles. However, when particles exhibit wave-like properties, a classical description is no longer valid. Quantum molecular dynamics methods are available, but they are restricted to very small systems as their computational costs scale exponentially with the number of particles. To treat larger systems, one can resort to mixed quantum-classical methods, which treat a key part of the system (i.e., the subsystem) quantum mechanically and the remainder (i.e., the bath) classically. Over the years, a number of mixed quantum-classical dynamics algorithms have been developed. The most accurate of them perform very well, but at high computational costs. Recently, we developed a method that exhibits a favourable balance between computational cost and accuracy. In its present formulation, however, this method is restricted to systems whose potential energies can be expressed in polynomial form and whose subsystems quickly lose memory of the bath dynamics. Thus, the first part of our research program will focus on advancing this methodology along several directions to make it more general, accurate, and efficient. The result promises to be a very powerful tool for simulating the dynamics of mixed quantum-classical systems. The second part of our research program will focus on applying both the present and future formulations of our mixed quantum-classical methodologies to a host of quantum energy transfer/storage processes of fundamental and technological importance. Specifically, we will explore quantum heat transfer processes involved in molecular electronics and nanophononics applications, and energy storage in quantum batteries. Our goals will be to gain an in-depth understanding of the factors that influence the rates/mechanisms of the heat transfer in a variety of molecular systems, and to propose practical designs for quantum batteries. The knowledge gained by this research will ultimately aid in the development of robust, efficient, and controllable nanoscale devices for use in quantum technologies.