We have revisited the 2D spectroscopy of the excitation energy transfer in the Fenna–Matthews–Olson (FMO) protein. Based on 2D spectroscopic signatures, the energy transfer dynamics in the FMO protein has been argued to be supported by long-lived electronic quantum coherence on timescales up to 1.5 ps. In contrast, our analysis, based on experimental data and confirmed by theoretical calculations, shows that the electronic decoherence occurs within 60 fs, in agreement with typical dephasing times in systems under these conditions. Given the relatively well-defined structure of the FMO protein, and comparative couplings between chlorophylls to other photosynthetic systems, the observed extremely fast decoherence should be viewed as general, bringing to question any significant quantum coherent transport contributions to photosynthesis.

Abstract