Excitation energy transfer in light-harvesting systems: Effect of the initial state

Light harvesting is a problem that has attracted interest for a long time. It became active again in recent years stimulated by suggestions of quantum effects in energy transport. Recent experiments found evidence that BChla 1 and BChla 6 are the first ones to be excited in the Fenna-Matthews-Olson (FMO) protein; theoretical studies, however, are mostly restricted to considering the exciton in BChla 1 initially. In this paper, we study the energy transport in the FMO complex by taking different initial states into account. The decoherence rates are optimized for maximal transport efficiency. Dependence of the energy transfer efficiency on the initial states is given and discussed. Effects of fluctuations in the site energies and couplings are also examined.