Open Quantum Dynamics: Memory Effects and Superactivation of Backflow of Information

We investigate the divisibility properties of the tensor products ${\mathrm{\Lambda }}_t^{(1)}\otimes {\mathrm{\Lambda }}_t^{(2)}$ of open quantum dynamics ${\mathrm{\Lambda }}_t^{(1,2)}$ with time-dependent generators. These dynamical maps emerge from a compound open system $S_1+S_2$ that interacts with its own environment in such a way that memory effects remain when the environment is traced away. This study is motivated by the following intriguing effect: one can have Backflow of Information (BFI) from the environment to $S_1+S_2$ without the same phenomenon occurring for either $S_1$ and $S_2$. We shall refer to this effect as the Superactivation of BFI (SBFI).