New Computational Methods for Quantum Dynamics of Large Systems

超越Born-Oppenheimer近似和对核运动的经典描述，对于促进我们对具有重要技术意义的生物和人工系统中的光化学过程的理解和控制的能力变得越来越重要。通常，光化学涉及多个电子态，而发展良好的Born-Oppenheimer分子动力学装置并不适用，因为核运动涉及多个电子态之间的切换。在许多情况下，电子自由度并不是唯一的量子成分，忽略零点运动、隧穿、量子化能级和相干能量转移可能会导致理论和实验之间的严重差异。在像视紫红质和细菌视紫红质这样的生物大分子中观察到量子效应的例子越来越多。为了更深入地了解这些观测，计算输入是至关重要的。不幸的是，量子力学定律实际上只能对相对较小的系统进行模拟。因此，至关重要的是进一步扩展计算技术，在现实模拟中包括重要的量子效应。这项工作的主要前提是，仍然有可能推导出一组相对较小的集体自由度，其动力学具有高度纠缠的量子性质，而其他自由度的动力学更简单，可以用计算要求较低的方法建模。在这项工作中，我们想要正式发展这些想法，以便获得定性和定量的工具，用于计算各种光活性蛋白质中的量子现象。

Going beyond the Born-Oppenheimer approximation and classical description of the nuclear motion becomes increasingly important for advancing our understanding and ability to control photochemical processes in biological and artificial systems of technological importance. Usually, photochemistry involves more than one electronic state and the well developed apparatus of Born-Oppenheimer molecular dynamics is not applicable because the nuclear motion involves switching between multiple electronic states. In many cases, electronic degrees of freedom are not the only quantum components and neglecting zero-point motion, tunneling, quantized energy levels and coherent energy transfer can cause severe discrepancies between theory and experiment. There is an increasing number of examples where quantum effects have been observed in large biological molecules like rhodopsin and bacteriorhodopsin. To obtain deeper understanding of these observations computational input is crucial. Unfortunately, quantum mechanical laws can be practically simulated for only relatively small systems. Thus, it is paramount to extend further computational techniques that would include important quantum effects in realistic simulations. The main premise in such undertaking is that it is still possible to derive a relatively small set of collective degrees of freedom whose dynamics has highly entangled quantum character while dynamics of other degrees of freedom is simpler and can be modeled with less computationally demanding approaches. In this work we would like to formally develop these ideas in order to obtain qualitative and quantitative tools for computational modelling of quantum phenomena in various photo-active proteins.