Comparison between Decoherence time for a Two-state Spin 1/2 System with   Its Corresponding Quantum Retrieval Period
  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. 
Afshin Shafiee and Arash Tirandaz
quant-ph