Le mardi 29 septembre à 16H en vidéoconférence https://www.twitch.tv/evrardalexandre
This thesis presents experiments realized with ultracold atomic gases of dysprosium. This element has specific properties such as a large spin J=8 and tunable light-spin couplings originating from significant tensor light-shift contributions close to resonance. An overview of the experimental setup is given, from the magneto-optical trap to the evaporative cooling. In particular we present the role of the tensor light-shift in the in-trap Doppler cooling. Details on the use of spatial modulation to tune the shape of an optical dipole trap are also given.
In the second part we describe the preparation of squeezed and ‘oversqueezed’ spin states as well as Schrödinger cat states using light-induced spin couplings. The magnetic sensitivity of these states is characterized using Ramsey spectroscopy. The Husimi function is reconstructed from populations measurement along various directions, also allowing us to compute the purity of the prepared states.
While squeezed states show an increased metrological gain, Ramsey spectroscopy fails to account for the sensitivity of oversqueezed states. The Hellinger distance is used to extend the notion of metrological gain and the sensitivity measured in this case saturates the Cramér-Rao bound. Finally a system of 16 indistinguishable interacting spins 1/2 is realized. In the third part we present the measurement of pairwise entanglement from photon absorption measurements, which was not realized experimentally.
Finally we present two projects where spatial degrees of freedom are added to the dynamics of internal levels. The first one consists in the realization of a system analogous to the Landau Hamiltonian of a charged particle in a magnetic field, with one spatial dimension and one synthetic dimension. The second project uses two spatial dimensions and exhibits an artificial magnetic field originating from position-dependent light-shifts.