Decoherence induced by a composite environment

We study the decoherence induced by the environment over a composite quantum system, comprising two coupled subsystems A and B, which may be a harmonic or an upside-down oscillator. We analyze the case in which the B subsystem is in direct interaction with a thermal bath, while the other remains isolated from the huge reservoir. We compare the results concerning the decoherence suffered by the A subsystem.

Figure 1

(Color online) Decoherence factor $\Gamma \left(t\right)$. Isolated composite system decoheres first for the (d) case (figures on the top). Plots in the middle and bottom are the decoherence factors for ${\gamma }_0{k}_{B}T=1$ and 100, respectively. Case (b) is more decoherent. On the left, both frequencies of the subsystems A and B are of the same order of magnitude $(\omega \approx \Omega )$ and on the right we show the case $\omega >\Omega$.