Non-Markovian evolution of a two-level system interacting with a fluctuating classical field via dipole interaction

We address memory effects in the dynamics of a two-level open quantum system interacting with a classical fluctuating field via dipole interaction. In particular, we study the backflow of information for a field with a Lorentzian spectrum, and reveal the existence of two working regimes, where memory effects are governed either by the energy gap of the two-level system, or by the interaction energy. Our results show that non-Markovianity increases with time, at variance with the results obtained for dephasing, and in spite of the dissipative nature of the interaction, thus suggesting that the corresponding memory effects might be observed in practical scenarios.