复杂生物开放系统中的量子相干控制

Quantum coherence plays a fundamental and vital role to make quantum systems greatly outperform their classical counterparts. This intriguing feature was first thought not to survive in the warm, wet and noisy biological environments, due to their strong and ubiquitous noise and fluctuations. However, recent experiments observed long-lasting time-dependent oscillations and suggest that quantum coherence could exist in complex light-harvesting systems, and speed up energy transfer efficiency. This leads to the rapid emergence of theoretical and experimental exploration in quantum biology, prominently in photosynthesis and avian compass mechanisms. To understand whether nature already takes advantages of non-trivial quantum effects, rooted in quantum coherence, to optimize functional control in biological systems during long-time natural evolution, is our main motivation. Making use of Ehrenfest guided multi-configurational coupled coherent states, integrated with other numerical methods, we aim to: (i) elucidate the non-equilibrium interplay between the intrinsic electronic degrees of freedoms and the protein (and solvent) environment in light-harvesting systems in the intermediate coupling region, where traditional perturbative and Markovian assumptions no longer hold; (ii) reveal the possible existence of coherent quantum effects and their potential biological functional contributions from highly structured environments, in either the time or the frequency domains; (iii) harness beneficial environment stimulations as tools for developing artificial bio-mimetic light harvesting apparatus. Hopefully, it will turn out nature is already ahead from us in the quest for harnessing quantum resources.

量子相干性使量子系统远优于其相应的经典系统。这奇异的性质，起初被认为：不会存在于温热潮湿嘈杂的生物系统中，因为那里强烈的噪声扰动无时不在。但是，近年来实验上观测到的长时间振荡，表明量子相干：可能存在于光合作用生物系统中，并且其加快了能量传输的效率。这迅速掀起了：理论与实验上对量子生物学的探索，尤其光合作用与鸟类的导航领域。本课题的出发点是：探究是否在长期的自然演化中，生物早已学会利用：起源于量子相干的非寻常效应，来优化生理功能。我们将集成多维耦合相干态与其他数值模拟方法：(1)阐释光合作用系统中，内在的电子自由度与蛋白质环境间的相互作用机制—在非微扰与非马科夫的中间耦合区域；(2)揭示可能存在的量子相干效应，以及（具有丰富特征的）生物环境可能带来的功能上的优化；(3)将有利的环境反馈机制，作为研发人工仿生光采集器件的设计原理。希望最终的结果是：自然界早已利用了量子效应，只是未被我们发现。

许多光合作用系统中观测到的长时间相干现象，激发了探寻生物系统中是否可能存在量子效应的广泛兴趣。接近100%的激发子能量传输效率，驱动产生了多种巧妙捕捉复杂环境结构中非马科夫效应的数值计算方法。基于多维耦合相干态的方法，我们首先研究单个自旋玻色开放系统，其中慢环境具有记忆效应；其次，在单激发态的子空间下，将分子二聚物转换为一个有效的二能级系统，将两个节点所在的热库合并为单个新的热库，我们研究了过阻尼与无阻尼谐振环境下：节点的布居数随时间的演化。我们数值模拟的结果与文献中反应坐标主方程的结果：在一定的时间与耦合强度内（例如激发子能量传输中的典型参数），比较一致。通过集成其他数值方法的思想，希望我们的数值方法可作为分析复杂光合作用系统中环境所扮演的真实角色的强有力工具。