  We show how the dispersive regime of the Jaynes-Cummings model may serve as a
valuable tool to the study of open quantum systems. We employ it in a bottom-up
approach to build an environment that preserves qubit energy and induces varied
coherence dynamics. We then present the derivation of a compact expression for
the qubit coherence, applied here to the case of a finite number of thermally
populated modes in the environment. We also discuss how the model parameters
can be adjusted to facilitate the production of short-time monotonic decay
(STMD) of the qubit coherence. Our results provide a broadly applicable
platform for the investigation of energy-conserving open system dynamics which
is fully within the grasp of current quantum technologies.
