Exciton Transfer in Photosynthesis and Engineered Systems: Role of Electronic Coherence and the Environment
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CitationRebentrost, Frank. 2012. Exciton Transfer in Photosynthesis and Engineered Systems: Role of Electronic Coherence and the Environment. Doctoral dissertation, Harvard University.
AbstractRecent experiments show evidence for long-lived electronic coherence in several photosynthetic complexes, for example in the Fenna-Matthews-Olson complex of green sulfur bacteria. The experiments raise questions about the microscopic reasons for this quantum coherence and its role to the functioning of these highly evolved biological systems. The present thesis addresses both questions. We find that an interplay of electronic coherence and the fluctuating phonon environment is responsible for the high exciton transport efficiency in these complexes and generalize this idea to the concept of environment-assisted quantum transport (ENAQT). In addition, we quantify the contribution of coherent dynamics to the efficiency and thus to the biological functioning. We determine the effect of temporal (non-Markovian) and spatial correlations and develop an ab initio propagation method based on atomistic detail which predicts the long-lived coherence. The research in photosynthetic energy transfer can inspire new designs for the control of excitons in engineered systems. We develop a method for computing the Forster coupling between semiconductor nanoparticle quantum dots. The focus is on the size and shape dependence and the presence of a spatially varying dielectric environment and metallic gates. A separation of the wavefunction into slowly and fast varying part provides the basis for an efficient computation on a real-space grid. Finally, the simulation of structured models of photosynthetic energy transfer is a challenging task using conventional computing resources. To this end, we propose a special-purpose superconducting device based on flux quantum bits and quantum LC resonators and show that parameters can be engineered such that this simulation becomes possible.
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