Martin Plenio, Imperial College London
Lecture to the Royal Society, 14 October 2008
Martin Plenio’s lecture of October 14 2008 has provided an interesting footnote to the Engel paper reviewed immediately above. In photosynthesis, the chlorophyll molecule is 98% efficient in transporting energy. Energy is absorbed in the form of light. The molecule supports excitation and oscillation of electrons, and allows the exploration of pathways in the molecule. A classical system would only be 60-70% efficient in transporting energy, but the chlorophyll molecule is 98% efficient. The molecule is at 300 degrees Kelvin or room temperature. Given the high temperature, Plenio thinks that there is likely to be some dephasing of the light quanta, but contrary to the normal view that this would be the end of any quantum processing, he considers that the efficiency of energy transportation could actually be enhanced by some limited dephasing. To illustrate his point, he referred to a well known experiment in which a beam of light is split as it passes through one beam splitter, and is later rejoined at a second beam splitter. In this situation, only one or two possible detectors beyond the second beam splitter will be activated. However, if one part of the split light beam is measured, either of the detector may subsequently be activated. Plenio thinks that the analogous situation of the activation of extra ‘detectors’ within chlorophyll could allow even more paths to be explored and even greater efficiency of energy transport.