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Quantum entanglement in photosynthetic light-harvesting complexes

Nature Physics volume 6, pages 462–467 (2010)Cite this article

Abstract

Light-harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long timescales, despite the decohering effects of their environments. Here, we analyse entanglement in multichromophoric light-harvesting complexes, and establish methods for quantification of entanglement by describing necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement. These methods are then applied to the Fenna–Matthews–Olson protein to extract the initial state and temperature dependencies of entanglement. We show that, although the Fenna–Matthews–Olson protein in natural conditions largely contains bipartite entanglement between dimerized chromophores, a small amount of long-range and multipartite entanglement should exist even at physiological temperatures. This constitutes the first rigorous quantification of entanglement in a biological system. Finally, we discuss the practical use of entanglement in densely packed molecular aggregates such as light-harvesting complexes.

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Figure 1: The light-harvesting apparatus of green sulphur bacteria and the FMO protein.
Figure 2: Global entanglement in the FMO protein.
Figure 3: Bipartite entanglement in the FMO protein when the initial state is an excitation localized on site 1.
Figure 4: Bipartite entanglement in the FMO protein when the initial state is an excitation localized on site 6.

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Acknowledgements

We are grateful to Y-C. Cheng, J. Dawlaty, V. Vedral and M. Plenio for conversations and comments. This material is based on work supported by DARPA under award No N66001-09-1-2026. This work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the US Department of Energy under contract No DE-AC02-05CH11231 and by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, US Department of Energy under contract DE-AC03-76SF000098. A.I. appreciates the support of a Japan Society for the Promotion of Science (JSPS) Postdoctoral Fellowship for Research Abroad.

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Authors and Affiliations

  1. Berkeley Center for Quantum Information and Computation, Berkeley, California 94720, USA

    Mohan Sarovar & K. Birgitta Whaley

  2. Department of Chemistry, University of California, Berkeley, California 94720, USA

    Mohan Sarovar, Akihito Ishizaki, Graham R. Fleming & K. Birgitta Whaley

  3. Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

    Akihito Ishizaki & Graham R. Fleming

Authors
  1. Mohan Sarovar
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Calculations were carried out by M.S. and A.I. All authors contributed extensively to the planning, discussion and writing up of this work.

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Correspondence to Mohan Sarovar.

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Sarovar, M., Ishizaki, A., Fleming, G. et al. Quantum entanglement in photosynthetic light-harvesting complexes. Nature Phys 6, 462–467 (2010). https://doi.org/10.1038/nphys1652

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