Title: The impact of decoherence on the route to equilibrium

Abstract: We study the time evolution of a single qubit when coupling to a bath, within the framework of projection operator method. Employing the so-called modified Redfield theory which also treats the energy conserving interaction non-perturbatively, we are able to study the regime beyond the scope of the usual approach. The reduced equations of motion for the qubit are derived in a idealistic system where both the bath and the interactions are modeled by Gaussian distributed random matrices. In strong decoherence regime, a simple relation between the bath correlation function and decoherence process induced by energy conserving interaction is found. It implies that energy conserving interaction slows down the relaxation process, which leads to a zeno freezing if it is sufficiently strong.Furthermore, our results are also confirmed in numerical simulations.