We present numerically exact results for the quantum coherent energy transfer
in the Fenna-Matthews-Olson molecular aggregate under realistic physiological
conditions, including vibrational fluctuations of the protein and the pigments
for an experimentally determined fluctuation spectrum. We find coherence times
shorter than observed experimentally. Furthermore we determine the energy
transfer current and quantify its "quantumness" as the distance of the density
matrix to the classical pointer states for the energy current operator. Most
importantly, we find that the energy transfer happens through a
"Schr\"odinger-cat" like superposition of energy current pointer states.Comment: enlarged and final version, 7 pages, 5 figure
