Exact coherence dynamics mediated by a small environment

We study the non-equilibrium entanglement dynamics of a qubit system coupled to a small environment consisting of only two harmonic oscillators. We report several analytic and numerical results related to the modulated concurrence dynamics of two-qubit systems via correlated environmental modes. In particular, we show that the correlation between the two components of the environment can serve as an enhancer for either fast decay or fast generation of the two-qubit entanglement.