• ultracold atoms
• polarizability
• optical trapping
• dipolar gases

This thesis centers on the study of dipolar quantum mixtures of strongly magnetic lanthanide atoms. Differently from alkali-based quantum gases, which feature a short-range and isotropic interaction among the atoms, magnetic lanthanides exhibit an additional interaction, namely the dipole-dipole interaction, which is long-range and anisotropic. Up to now, experiments on lanthanides focus either on erbium (Er) or dysprosium (Dy). This master thesis aims at going beyond the single-species operation by combining these two species for realizing a quantum mixture. The aim of the thesis, reported here, was to design, realize and implement an optical dipole trap, ables to simultaneously confine ultracold Er and Dy atoms. The design of the dipole trap relies on the atom-light interaction properties. The multi-valence electrons character of Er and Dy gives rise to a complex and rich energy spectrum. First task was thus to simulate the trapping potential for the atoms with a determination of the most important parameters for an effcient confinement. Once identified the optical parameters, the second part was dedicated to the experimental realization of the optical dipole trap. The trap possesses a tunable geometry, based on time-averaged potentials created by an acousto-optic deflector. The tunability is a fundamental tool to investigate phenomena triggered by the anisotropic character of the dipole-dipole interactions. It is exploited to increase the loading effciency of the optical dipole trap reaching the "mode-matching" condition with the magneto-optical trap. Additionally,
it can be used to optimize the efficiency of the evaporative cooling, determined by the elastic collision rate, tuning the density. Finally, we describe the implementation of the optical setup in the experiment and a preliminary characterization of the optical dipole trap, demonstrating an efficient loading for both species and measuring the trap frequencies, which enable to extract the value of the atomic polarizabilities. So far, the polarizability measurements with lanthanides have shown large discrepancy among them. Our experiment is able to determine the polarizability ratio of Er and Dy, in which the sistematical errors cancel out, offering a better understanding of their atomic properties.