New Computational Methods for Quantum Dynamics of Large Systems

超越Born-Oppenheimer近似和核运动的经典描述对于提高我们对生物和人工系统中具有技术重要性的光化学过程的理解和控制能力变得越来越重要。通常，光化学涉及一个以上的电子状态和玻恩-奥本海默分子动力学的发达设备是不适用的，因为核运动涉及多个电子状态之间的切换。在许多情况下，电子自由度并不是唯一的量子分量，忽略零点运动、隧穿、量子化能级和相干能量转移会导致理论和实验之间的严重差异。有越来越多的例子，量子效应已被观察到在大的生物分子，如视紫红质和细菌视紫红质。为了更深入地了解这些观测结果，计算输入至关重要。不幸的是，量子力学定律只能在相对较小的系统中进行实际模拟。因此，最重要的是扩展进一步的计算技术，包括在现实模拟中的重要量子效应。这样做的主要前提是，仍然有可能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特性，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，我们想正式开发这些想法，以获得定性和定量的工具，在各种光敏蛋白质的量子现象的计算建模。

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.