Correlated Quantum Dynamics of a Single Atom Collisionally Coupled to an Ultracold Finite Bosonic Ensemble

Abstract. We explore the correlated quantum dynamics of a single atom, regarded as an open system, with a spatio-temporally localized coupling to a finite bosonic environment. The single atom, initially prepared in a coherent state of low energy, oscillates in a one-dimensional harmonic trap and thereby periodically penetrates an interacting ensemble of NA bosons, held in a displaced trap. The non-equilibrium quantum dynamics of the total system is simulated by means of the ab-initio Multi-Layer Multi-Configuration Time-Dependent Hartree Method for Bosons. We show that an inter-species interaction-induced level splitting leads to an accelerated energy transfer for larger NA, which becomes less complete at the same time. During the energy transfer, the single atom temporarily attains non-coherent states and mainly induces singlet and doublet excitations in the finite bosonic environment, whose dynamical quantum depletion becomes suppressed for larger NA. System-environment correlations prove to be significant except for times when the excess energy distribution among the subsystems is highly imbalanced. These correlations result in incoherent energy transfer processes, which accelerate the early energy donation of the single atom, and (dis-)favour certain energy transfer channels depending on the instantaneous direction of transfer. PACS numbers: 03.75.Gg, 67.85.De, 67.85.Fga rX i