  We study the open system dynamics of a harmonic oscillator coupled with an
artificially engineered reservoir. We single out the reservoir and system
variables governing the passage between Lindblad type and non-Lindblad type
dynamics of the reduced system's oscillator. We demonstrate the existence of
conditions under which virtual exchanges of energy between system and reservoir
take place. We propose to use a single trapped ion coupled to engineered
reservoirs in order to simulate quantum Brownian motion.
