Probing the Bose glass-superfluid transition using quantum quenches of disorder

The disordered Bose-Hubbard model-a paradigm for strongly correlated and disordered bosonic systems(1)-is central to our understanding of quantum phase transitions(2). Despite extensive theoretical work on the disordered Bose-Hubbard model, little is known about the impact of temperature, the dynamical behaviour of quantum phases, and how equilibrium is affected during quantum phase transitions. These issues are critically important to applications such as quantum annealing(3-7) and electronics based on quantum phase transitions(8). Here, we use a quantum quench of disorder in an ultracold lattice gas to dynamically probe the superfluid-Bose glass quantum phase transition at non-zero temperature (Fig. 1). By measuring excitations generated during the quench, we provide evidence for superfluid puddles in the Bose glass phase and produce a superfluid-Bose glass phase diagram consistent with completely constrained, finite temperature, and equilibrium quantum Monte Carlo simulations. The residual energy from the quench, which is an efficacy measure for optimization through quantum annealing, is unchanged for quench times spanning nearly a hundred tunnelling times.