  We investigate the non-Markovian dynamics of a qubit-oscillator system
embedded in a noisy environment by employing the hierarchical equations of
motion approach. It is found that the decoherence rate of the whole
qubit-oscillator-bath system can be significantly suppressed by enhancing the
coupling strength between the qubit and the harmonic oscillator. Moreover, we
find that the non-Markovian memory character of the bath is able to facilitate
a robust quantum coherent dynamics in this qubit-oscillator-bath system. Our
findings may be used to engineer some tunable coherent manipulations in
mesoscopic quantum circuits.
