Quantum coherence spectroscopy reveals complex dynamics in bacterial light-harvesting complex 2 (LH2)

Elad Harel, Gregory S. Engel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

173 Scopus citations


Light-harvesting antenna complexes transfer energy from sunlight to photosynthetic reaction centers where charge separation drives cellular metabolism. The process through which pigments transfer excitation energy involves a complex choreography of coherent and incoherent processes mediated by the surrounding protein and solvent environment. The recent discovery of coherent dynamics in photosynthetic light-harvesting antennae has motivated many theoretical models exploring effects of interference in energy transfer phenomena. In this work, we provide experimental evidence of long-lived quantum coherence between the spectrally separated B800 and B850 rings of the light-harvesting complex 2 (LH2) of purple bacteria. Spectrally resolved maps of the detuning, dephasing, and the amplitude of electronic coupling between excitons reveal that different relaxation pathways act in concert for optimal transfer efficiency. Furthermore, maps of the phase of the signal suggest that quantum mechanical interference between different energy transfer pathways may be important even at ambient temperature. Such interference at a product state has already been shown to enhance the quantum efficiency of transfer in theoretical models of closed loop systems such as LH2.

Original languageEnglish (US)
Pages (from-to)706-711
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number3
StatePublished - Jan 17 2012


  • Biophysics
  • Excitonic dynamics
  • Photosynthesis
  • Quantum biology
  • Ultrafast spectroscopy

ASJC Scopus subject areas

  • General


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