Coherent Speedup of Excitation Energy Transfer in PC645

The fundamental principle governing the robust excitation energy transfer (EET) in the light-harvesting complexes remained elusive. Recent spectroscopic observations of the EET attract attention toward the role of the quantum effects in the biological systems. In this study, along with the time evolution, the distance between the quantum states of the pigments is also considered for a detailed illustration of the effect of the quantum coherence on the speed of the excitation transfer. The comparative analysis of the coherently delocalized EET with the incoherent discrete hopping reveals that the coherent superposition speedup the excitation transfer process, for instance, with the initially localized excitation, coherence provides a ∼4-fold enhancement to the excitation transfer rate.