Quantum Effects in Biology

Biologists do not take a quantum physics course during their studies because so far they were able to make sense of biological phenomena without using the counterintuitive quantum laws of physics that govern the atomic scale. However, in recent years progress in experimental technology has revealed that quantum phenomena are relevant for fundamental biological processes such as photosynthesis, magneto-reception and olfaction. We have helped to initiate the development of this research field and are now working to discover how nature is harnessing quantum dynamics to optimize biological function.

Environment assisted biological quantum dynamics: It is remarkable that quantum phenomena can play a role in warm, wet and noisy biological systems. One important reason is that some biologically relevant phenomena take place on rather short timescales that prevent the environment from destroying quantum coherence completely. More interestingly a few years ago we proposed that environmental noise can actually collaborate with quantum dynamics to achieve the best possible efficiency in biological processes. We continue to explore this phenomenon with the aim of uncovering the design principles by which nature has optimized quantum biological function in noisy environments.

Environment assisted biological quantum dynamics: Biological environments are not merely creating white noise but do actually possess a complex spectral structure. Indeed, an important aspect of biological environments are vibrations which originate from proteins and embedded molecules. At specific frequencies this vibrational motion can be long-lived and interact in highly non-trivial fashion with electronic motion which we proposed to give rise to fast transport, molecular recognition or long-lived quantum coherence in biological systems.

Environment assisted biological quantum dynamics: Theory in this field needs to be verified by experiment. Indeed, recent advances in nonlinear optical spectroscopy have demonstrated the presence of long-lived quantum coherences in biological systems. These coherences reflect coherent features in biological processes, such as coherent transport and coherent electronic-vibrational (vibronic) coupling. Identification of the microscopic origin of experimentally observed coherences is a key to understanding the role of quantum effects in biological processes. We are studying how different structures of biological environments can be distinguished in experiments with the aim of unraveling the underlying mechanisms in biological processes and applying them to artificial systems.

Delocalization directs absorption: The early steps of photosynthesis involve the excitation of reaction centres (RCs) and light-harvesting (LH) units by light. Historically, the electronic coherence across RCs and LH units has been neglected as it does not play a significant role during the relatively slow energy-transfer steps of the primary process. However, we showed that spatially extended but short-lived excitonic delocalization across RC-LH units plays a relevant role in general photosynthetic systems, as it causes a redistribution of direct absorption towards the charge separation unit. We also contributed to the experimental verification of this effect.

  • F. Caycedo-Soler, C.A. Schroeder, C. Autenrieth, R. Ghosh, S.F. Huelga and M.B. Plenio. Quantum delocalization directs antenna absorption to photosynthetic reaction centers. E-print arxiv:1504.05470
  • C.A. Schroeder, F. Caycedo-Soler, S.F. Huelga and M.B. Plenio. Optical signatures of quantum delocalization over extended domains in photosynthetic membranes. E-print arxiv:1505.05485

Avian magneto-reception: It is well established that birds use the earth’s magnetic field to navigate during migration. How birds achieve this remarkable feat is a subject of current research. One proposed mechanism for magneto-reception is based on the radical pair mechanism which involves the quantum dynamics of electrons in interaction with their nuclear spin environment. We are exploring this hypothesis theoretically and aim to understand what the principles for the optimal design of such a quantum magnetic compass might be.