Engineering the Landau-Zener Tunneling of Ultracold Atoms in Tilted Potential

Abstract

A comprehensive study of the time-resolved Landau–Zener tunneling of a Bose– Einstein condensate in a tilted periodic potential is presented in this thesis. Several ways are discussed how to control the tunneling. In the first collection of our results, the tunneling from the ground band to the continuum is shown to depend crucially on the initial condition and system parameters, and also on the strength of atom-atom interactions. The use of different protocols enables us to access the tunneling probability in two different bases, namely, the adiabatic basis (eigenstates of the Hamiltonian with the potential) and the diabatic basis (free-particle momentum eigenstates). The structure of the survival probability and the measure of the tunneling time depend on the chosen basis. All these possibilities have been checked and proved in experiments. We go also beyond and propose a possibility to manipulate the tunneling probability of ultracold atoms in the tilted time-dependent stochastic potentials. Our theoretical and numerical results show that the tunneling in such a potential can be controlled by adding different types of colored noise. A scaling law is introduced for these results, which effectively reduces the parameter-dependence of the tunneling and leads to a better understanding of dynamics in the proposed noisy system.