title: Nonadiabatic coherent evolution of two-level systems under spontaneous decay.
abstract: In this Letter we extend current perspectives in engineering reservoirs by producing a time-dependent master equation leading to a nonstationary superposition equilibrium state that can be nonadiabatically controlled by the system-reservoir parameters. Working with an ion trapped inside a nonideal cavity, we first engineer effective interactions, which allow us to achieve two classes of decoherence-free evolution of superpositions of the ground and excited ionic levels: those with a time-dependent azimuthal or polar angle. As an application, we generalize the purpose of an earlier study [Phys. Rev. Lett. 96, 150403 (2006)10.1103/PhysRevLett.96.150403], showing how to observe the geometric phases acquired by the protected nonstationary states even under nonadiabatic evolution.
authors.affiliation: Departamento de Física, Universidade Federal de São Carlos, P.O. Box 676, São Carlos, 13565-905, São Paulo, Brazil.
authors.forename: F O
authors.initials: FO
authors.lastname: Prado
authors.forename: E I
authors.initials: EI
authors.lastname: Duzzioni
authors.forename: M H Y
authors.initials: MH
authors.lastname: Moussa
authors.forename: N G
authors.initials: NG
authors.lastname: de Almeida
authors.forename: C J
authors.initials: CJ
authors.lastname: Villas-Bôas