Quantum nonlocality in the excitation energy transfer in the Fenna-Matthews-Olson complex

摘要

The Fenna-Matthews-Olson (FMO) complex - a pigment protein complex involvedin photosynthesis in green sulfur bacteria - is remarkably efficient intransferring excitation energy from light harvesting antenna molecules to areaction center. Recent experimental and theoretical studies suggest thatquantum coherence and entanglement may play a role in this excitation energytransfer (EET). We examine whether bipartite quantum nonlocality, a propertythat expresses a stronger-than-entanglement form of correlation, exists betweendifferent pairs of chromophores in the FMO complex when modeling the EET by thehierarchically coupled equations of motion method. We compare the results fornonlocality with the amount of bipartite entanglement in the system. Inparticular, we analyze in what way these correlation properties are affected bydifferent initial conditions. It is found that bipartite nonlocality onlyexists when the initial conditions are chosen in an unphysiological manner andprobably is absent when considering the EET in the FMO complex in its naturalhabitat. It is also seen that nonlocality and entanglement behave quitedifferently in this system. In particular, for localized initial states,nonlocality only exists on a very short time scale and then drops to zero in anabrupt manner. As already known from previous studies, quantum entanglementbetween chromophore pairs on the other hand is oscillating and exponentiallydecaying and follow thereby a pattern more similar to the chromophorepopulation dynamics. The abrupt disappearance of nonlocality in the presence ofnonvanishing entanglement is a phenomenon we call nonlocality sudden death; astriking manifestation of the difference between these two types ofcorrelations in quantum systems.