Prof. Manolopoulos gives a seminar on semiclassical spin dynamics

Abstract: I have always been deeply suspicious about the emerging field of "quantum biology". What possible use could biology make of real-time quantum interference effects, which are rapidly quenched in (almost) any system coupled to a thermal bath at room temperature? So I was quite intrigued when my colleague Peter Hore asked me a couple of years ago to look into the semiclassical theory of spin dynamics and its application to biological radical pair recombination reactions. My initial reaction was that this was an excellent idea, because these reactions could surely be described semi-classically (i.e., without bothering to include any real-time quantum coherence effects). And I was right, at least to some extent. The simple semiclassical (SC) approach [1] certainly explains the operation of a prototypical "chemical compass" molecule [2] -- a carotenoid-porphyrin-fullerene triad that Peter's group have shown to be sensitive to an Earth-strength magnetic field -- and also the observed effect of an applied magnetic field on the electroluminescense of organic light emitting diodes [3]. However, there are now strong indications that the SC approach is not enough to explain the precision of the magnetic compass sense of migratory birds, and that this might well be a genuinely quantum mechanical (real-time interference) phenomenon [4]. If this turns out to be correct, it will be a truly spectacular example of "quantum biology"