Onset of thermalization in a Quantum Newton's Cradle

Bosons trapped in a blue-detuned 2D optical lattice can be made to approximate the integrable Lieb-Liniger model, but the approximation is imperfect. So while integrability would constrain an out-of-equilibrium Lieb-Liniger gas from thermalizing, slight non-integrability in quasi-1D gases can lead to thermalization. We study such gasses (Quantum Newton’s cradles) with a range of initial energies and 2D lattice depths and measure the evolution of their total energy. After accounting for the effects of spontaneous emission and 3-body loss, we infer that there is evaporative cooling, which implies the onset of thermalization.