  We theoretically investigate exciton relaxation dynamics in molecular
aggregates based on model photosynthetic complexes under various conditions of
incoherent excitation. We show that noise-induced quantum coherence is
generated between spatially-separated exciton states which belong to the same
or different energy transfer pathways, coupled via real and virtual transfer
processes. Such quantum coherence effects may be used to improve
light-harvesting efficiency and to reveal quantum phenomena in biology.
