Exciton transfer in photosynthesis and engineered systems

Recent 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