University of Chicago researchers have created a synthetic compound that mimics the complex quantum dynamics observed in photosynthesis and may enable fundamentally new routes to creating solar-energy technologies. Engineering quantum effects into synthetic light-harvesting devices is not only possible, but also easier than anyone expected, the researchers report in the April 19 edition of Science. The researchers have engineered small molecules that support long-lived quantum coherences. Coherences are the macroscopically observable behavior of quantum superpositions. Superpositions are a fundamental quantum mechanical concept, exemplified by the classic Schrodinger's Cat thought experiment, in which a single quantum particle such as an electron occupies more than one state simultaneously. Quantum effects are generally negligible in large, hot, disordered systems. Nevertheless, the recent ultrafast spectroscopy experiments in UChicago chemistry Prof. Greg Engel's laboratory have shown that quantum superpositions may play a role in the near perfect quantum efficiency of photosynthetic light harvesting, even at physiological temperatures. Photosynthetic antennae - the proteins that organize chlorophylls and other light-absorbing molecules in plants and bacteria - support superpositions that survive for anomalously long times. Many researchers have proposed that organisms have evolved a means of protecting these superpositions. The result: improved efficiency in transferring energy from absorbed sunlight to the parts of the cell that convert solar energy to chemical energy. The newly reported results demonstrate that his particular manifestation of quantum mechanics can be engineered into human-made compounds.
