title: Aspects of quantum coherence in the optical Bloch equations.
abstract: Aspects of coherence and decoherence are analyzed within the optical Bloch equations. By rewriting the analytic solution in an alternate form, we are able to emphasize a number of unusual features: (a) despite the Markovian nature of the bath, coherence at long times can be retained; (b) the long-time asymptotic degree of coherence in the system is intertwined with the asymptotic difference in level populations; (c) the traditional population-relaxation and decoherence times, T1 and T2, lose their meaning when the system is in the presence of an external field, and are replaced by more general overall time scales; (d) increasing the field strength, quantified by the Rabi frequency Omega, increases the rate of decoherence rather than reducing it, as one might expect; and (e) maximum asymptotic coherence is reached when the system parameters satisfy Omega2=1(T1T2).
authors.affiliation: Chemical Physics Theory Group, Department of Chemistry, and Center for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6, Canada. asanz@chem.utoronto.ca
authors.forename: A S
authors.initials: AS
authors.lastname: Sanz
authors.forename: H
authors.initials: H
authors.lastname: Han
authors.forename: P
authors.initials: P
authors.lastname: Brumer