This paper investigates the dynamics of excitonic transport in photocomplex LHCII, the primary component of the photosynthetic apparatus in green plants. The dynamics exhibits a strong interplay between coherent processes mediated by the excitonic Hamiltonian, and incoherent processes due to interactions with the environment. The spreading of the exciton over a single monomer is well described by a proper measure of delocalization that allows one to identify two relevant time scales. An exciton initially localized in one chromophore first spreads coherently to neighboring chromophores. During this initial coherent spreading, quantum effects such as entanglement play a role. As the effects of a decohering environment come into play, coherence and decoherence interact to give rise to efficient and robust excitonic transport, reaching a maximum efficiency at the levels of decoherence found in physiological conditions. We analyze the efficiency for different possible topologies (monomer, dimer, trimer, tetramer) and show how the trimer has a particular role both in the antenna and the wire configuration.
Transport phenomena in photosynthetic systems have attracted a great deal of attention due to their potential role in devising novel photovoltaic materials. In particular, energy transport in light-harvesting complexes is considered quite efficient due to the balance between coherent quantum evolution and decoherence, a phenomenon coined Environment-Assisted Quantum Transport (ENAQT). Although this effect has been extensively studied, its behavior is typically described in terms of the decoherence's strength, namely weak, moderate or strong. Here, we study the ENAQT in terms of quantum correla…
Environment-Assisted Quantum Walks in Photosynthetic Energy Transfer
光合系统中的能量传递可以表现出量子效应，例如离域激子传递。最近，对于Fenna-Matthews-Olson（FMO）蛋白质复合物的动力学，已经通过实验证明了长寿命相干性的直接证据[Engel et al.，Nature 446，782（2007）]。然而，量子动力学过程与激子转移效率的相关性在很大程度上是未知的。在这里，我们开发了一个理论框架，用于研究量子干涉效应在分子阵列与Lindblad形式主义内的热浴相互作用的能量传递动力学中的作用。为此，我们推广连续时间量子行走的非幺正和温度依赖的动力学刘维空间来自微观哈密顿。通过能量转移效率及其敏感性的普适度量，探讨了相干和退相干过程的不同物理效应。特别是，我们证明了FMO复杂的自由哈密顿量和热波动的环境之间的有效相互作用导致能量转移效率从约70%大幅增加到99%。
