title: Environment-assisted quantum walks in photosynthetic energy transfer.
abstract: Energy transfer within photosynthetic systems can display quantum effects such as delocalized excitonic transport. Recently, direct evidence of long-lived coherence has been experimentally demonstrated for the dynamics of the Fenna-Matthews-Olson (FMO) protein complex [Engel et al., Nature (London) 446, 782 (2007)]. However, the relevance of quantum dynamical processes to the exciton transfer efficiency is to a large extent unknown. Here, we develop a theoretical framework for studying the role of quantum interference effects in energy transfer dynamics of molecular arrays interacting with a thermal bath within the Lindblad formalism. To this end, we generalize continuous-time quantum walks to nonunitary and temperature-dependent dynamics in Liouville space derived from a microscopic Hamiltonian. Different physical effects of coherence and decoherence processes are explored via a universal measure for the energy transfer efficiency and its susceptibility. In particular, we demonstrate that for the FMO complex, an effective interplay between the free Hamiltonian evolution and the thermal fluctuations in the environment leads to a substantial increase in energy transfer efficiency from about 70% to 99%.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, Massachusetts 02138, USA.
authors.forename: Masoud
authors.initials: M
authors.lastname: Mohseni
authors.forename: Patrick
authors.initials: P
authors.lastname: Rebentrost
authors.forename: Seth
authors.initials: S
authors.lastname: Lloyd
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
mesh_terms: D004735:Energy Transfer; D008390:Markov Chains; D008956:Models, Chemical; D010788:Photosynthesis; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D011789:Quantum Theory; D013696:Temperature
chemical_list: D011506:Proteins