  We consider the evolution of a two-state quantum system (a spin 1/2 particle)
in both the framework of standard quantum mechanics and under the decoherence
regime. The former approach on this issue is the well-known quantum flipping
process of a dichotomic system subjected to a time-dependent magnetic field. In
the latter approach, utilizing the Spin-Boson model to describe the interaction
of system with its environment, we derive the Born-Markov master equation to
obtain the decoherence time. It is possible to show that under some legitimate
conditions, one may find a potential conflict between the predictions of
decoherence theory and the result observed in a typical quantum flipping
experiment.
