The relative importance of quantum effects in biological systems has long been debated. At the molecular level, the discussion reduces to the spatial and temporal coherence of the corresponding wavefunction describing the biological response function. Coherent Control provides a direct measurement of the coherence properties within the molecular frame of reference. In this pursuit, Coherent Control protocols have illustrated fundamental differences between closed (isolated) and open (e.g. biological) quantum systems. Under weak field control, it was possible to illustrate phase dependent control over the primary photo-isomerization step of bacteriorhodopsin. These studies have now been complemented with 2D studies that show the unusual effect of strong nonadiabatic mixing of the trans/cis states by the very modes involved in barrier crossing. We have found that the reactant/product surfaces are directly coupled by the very modes involved in the structural transition. This observation illustrates just how highly optimized this process is as well as helps explain the highly directed nature of the associated light driven biological functions of the rhodopsin protein group. These observations indicate that quantum coherence effects can persist long enough, even along reaction coordinates of complex biological systems , to manifest interference effects in barrier crossings. This issue of long lived coherences will be critically examined. Based on different distinct features in 2D spectra that must be self consistent,, the evidence to date points to a role for vibrational coherences in optimization of biological functions. These results taken together posit new questions with respect to properly describing the microscopic processes involved in the photoinduced processes driving biological functions

Do we live in a quantum world? A new twist

247th National Meeting (2014)

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