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## Dissipative Yb gases

### Lorenzo Rosso (LPTMS)

Ultracold atomic gases are an experimental platform to study quantum many-body physics, allowing the observation of non-trivial many-body phenomena in and out of equilibrium, thus making their theoretical understanding a priority. They usually feature a high degree of control over system parameters and allow for an almost perfect decoupling from the surrounding environment. However, despite the tremendous experimental progress, a perfect isolation has never been reached, for instance because of particle losses, causing energy relaxation and decoherence phenomena. As such, dissipation is generally seen as an enemy to be fought harshly since it tends to destroy and wash out the interesting quantum effects that can be investigated. On the other hand, a research line that developed in the last decade has shown that this is not always the case. In particular, the interplay between the coherent unitary evolution and the coupling to the environment can lead to a non-trivial dynamics and to stationary states featuring strong quantum correlations and critical behaviors. Although of primary interest to understand the limitations of the simulation of quantum many-body physics, a complete theoretical description of the effect of losses on correlated quantum gases is still lacking. Even if several experiments have studied the dynamics of correlated one-dimensional quantum gases in the presence of losses, both in the bosonic and fermionic cases, the theoretical characterisation of the interplay between the unitary and lossy dynamics has only recently emerged as an important challenge and it is currently starting to attract novel attention. This thesis aims at the study of lossy correlated gases. Our work puts a particular emphasis on the theoretical characterisation of the interplay between the Hamiltonian unitary dynamics and losses. We consider different bosonic and fermionic models in the presence of mainly two-body losses, we devise effective descriptions for the relevant degrees of freedom of such systems, capable of predicting the real time dynamics of the main observables, which we then benchmark against exact numerical simulation of the full master equation.

Jury : Leonardo Mazza (directeur de thèse), Igor Lesanovsky (rapporteur), Johannes Schachenmayer (rapporteur), Isabelle Bouchoule (examinatrice), Andrea De Luca (examinateur), Laurent Sanzhez-Palencia (examinateur)