Quantum coherence in light-harvesting complexes
Light-harvesting complexes like FMO (Fenna-Matthews-Olson) in green sulfur bacteria achieve near-perfect quantum efficiency by exploiting quantum coherence — excitons explore multiple energy-transfer pathways simultaneously rather than hopping classically. The 2007 Fleming lab experiments observed long-lived (660 fs) quantum beating at room temperature, suggesting that photosynthesis harnesses quantum mechanics to optimize energy funneling to the reaction center. The interplay of quantum coherence with environmental "noise" from protein vibrations may actually enhance, rather than degrade, transfer efficiency — a phenomenon called environment-assisted quantum transport (ENAQT).