title: Transient quantum coherent response to a partially coherent radiation field.
abstract: The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal "toy" model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.
authors.affiliation: Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Zaheen S
authors.initials: ZS
authors.lastname: Sadeq
authors.affiliation: Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Brumer
mesh_terms: D004583:Electrons; D004735:Energy Transfer; D008027:Light; D010798:Phycocyanin / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D011506:Proteins; C039637:phycocyanin 645; D010798:Phycocyanin