Quantum coherence in single biomolecules measured by multidimensional optical micro-spectroscopy

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Life is based on the intricate interactions between a multitude of biomolecules, including lipids, proteins, and DNA. They are dynamical in nature and maintain the non-equilibrium state of life. To understand the machinery of life, the interactions between the molecules are finely tuned as a result of long-term evolution. While many mechanisms can be described by non-equilibrium thermodynamics making use of local equilibrium with spatial gradients of concentrations, some examples have been highlighted which show the importance of quantum coherence of excitations over molecular complexes [10.1098/rsif.2018.0640]. Specifically in the functions of sensing (smell, vision) and photosynthesis, the interplay between long range coherent coupling, e.g. via dipole-dipole interaction, and coupling to local vibrations, is an intriguing mechanism being investigated [10.1126/science.1235820]. Building on the pioneering work of the supervisor's laboratory in developing advanced laser micro-spectroscopy techniques, this project will investigate the coherent quantum dynamics of single biomolecule functional units.You will translate the two-dimensional coherent micro-spectroscopy technique "Heterodyne Spectral Interferometry", developed and available in our laboratory, from the investigations of semiconductor nanostructures [10.1038/ncomms2764, 0.1038/nphoton.2016.2], towards this ambitious goal. The evolution of the coherence in light-harvesting complexes will be studied from low temperatures (5K), where long lived coherence is expected, up to room temperature, where the thermal excitations reduce the coherence time and the biomolecules are in their operating range. This will allow you to identify the mechanisms of decoherence and verify if nature has tuned the balance optimally at living conditions of the related organisms, such as algae, and sulphur/purple bacteria. Using this insight, we plan to study these coherences in artificial light-harvesting structures [10.1126/science.1249771], which are being developed as a green energy source, in order to understand and optimize their performance.