Quantum Coherence in Photosynthetic Exciton Dynamics

We present numerically exact results for the electronic energy transfer dynamics in the Fenna-Matthews-Olson (FMO) molecular aggregate. In particular, we determine its single excitation subspace dynamics within an open quantum dynamics approach which is based on parameters for the dipolar couplings, site energies and their respective fluctuations. We study and compare the dynamics for parameters according to several models available in the literature. Depending on the model used we find quantum coherent dynamics with coherence times exceeding experimentally observed times but also shorter times for other models. Even strongly overdamped decay of the site populations with no coherent population dynamics is observed for model parameters based on atomistic molecular dynamics. Thus, theoretical understanding at the present stage can neither support nor rule out a picture of quantum coherent energy transfer in natural photosynthesis.