HQOC/ITAMP Joint Quantum Sciences Seminar Wednesday, November 14 * 4:00 PM * Jefferson 250 Guest Presenter: Alan Aspuru-Guzik, Harvard University "Molecules as Quantum Processors: Ultrafast quantum process tomography to study exciton transport in molecule systems" Ultrafast experiments carried out on several photosynthetic complexes from many groups around the world have shown long-lived (~100 fs - 1 ps) quantum oscillations in two-dimensional optical spectra. Evidence suggests that these are electronic in nature, but they could be vibrational in character. Our group introduced and adapted a powerful tool from quantum optics and quantum information, quantum process tomography, for its use in condensed-phase molecular experiments. We also have recently proposed an ultrafast pump-probe scheme to distinguish between vibrational and electronic coherences as a/ witness/ for electronic coherence. In this colloquium-level talk, I will describe QPT and its application to ultrafast molecular experiments. I will describe the first experimental application of the technique, which is an ongoing collaboration with Keith Nelson (MIT) on a double-walled self-assembled molecular aggregate. Our QPT results show evidence of coherent exciton transport between two J-aggregates at room temperature. Finally, I will conclude with our simulations of a natural molecular self-assembled aggregate: the Chlorosome antenna complex of green-sulfur bacteria. These simulations provide insight into the inner workings of the light harvesting apparatus of this remarkable organism that can survive in very low-light conditions. *Student presentation by: Arghavan Safavi-Maini "Quantum Phases of Dipolar Bosons in Bilayer Geometry" * * * *Refreshments will be served. * -- Joan Hamilton Faculty Assistant to Profs. Lukin and Greiner HQOC Administrative Coordinator Harvard University Department of Physics 17 Oxford Street Cambridge, Ma 02138 Phone 617-496-2544 HUCTW Local Representative for the Department of Physics