The question, to which extent quantum coherence is exploited in biological systems, e.g., in order to enhance their efficiency, has attracted much attention in the recent years. Examples of interest are in the process of light harvesting in photosynthesis, or the radical pair mechanism as a model for avian magneto-reception. In our research, we are exploring the general conditions for the existence of quantum coherence and entanglement in biological systems, as well as their possible role for biological function.
- We study the models of non-equilibrium quantum systems that are capable of generating and sustaining entanglement in a noisy environment. We are interested in such models both from the perspective of building a noise-resilient quantum computer that could operate under room-temperature conditions, and from the perspective of identifying entanglement-sustaining molecular-scale mechanisms in biological systems.
- We study the radial pair mechanism in spin chemistry, which is believed to play a central role in avian magneto reception. We investigate the effect of multiple encounters and other sources of de-coherence in the radical pair mechanism, using both a stochastic collision model and a master-equation approach.
- We explore the use of molecular photo-switches to optically control the radical pair reactions and to test current theory used to describe spin-recombination reactions.
 H. J. Briegel and S. Popescu, A perspective on possible manifestations of entanglement in biological systems, in Quantum Effects in Biology, eds. M. Mohseni, Y. Omar, G. S. Engel, M. B. Plenio, Cambridge University Press (2014).
 J. Clausen, G. G. Guerreschi, M. Tiersch, and H. J. Briegel, Multiple re-encounter approach to radical pair reactions and the role of nonlinear master equations, J. Chem. Phys. 141, 054107 (2014) [arXiv:1310.6194].
 G. G. Guerreschi, M. Tiersch, U. Steiner, and H. J. Briegel, Optical switching of radical pair conformation enhances magnetic sensitivity, Chem. Phys. Lett. 572, 106 (2013) [arXiv:1206.1280].
 M. Tiersch, S. Popescu, and H. J. Briegel, A critical view on transport and entanglement in models of photosynthesis, Phil. Trans. R. Soc. A 370, 3771 (2012) [arXiv:1104.3883].
 J. M. Cai, S. Popescu, and H. J. Briegel, Dynamic entanglement in oscillating molecules and potential biological implications, Phys. Rev. E 82, 021921 (2010) [arXiv:0809.4906].
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