Diffusive and arrested transport of atoms under tailored disorder

Abstract

Ultracold atoms in optical lattices offer a unique platform for investigating disorder-driven phenomena. While static disordered site potentials have been explored in a number of experiments, a more general, dynamical control over site-energy and off-diagonal tunnelling disorder has been lacking. The use of atomic quantum states as synthetic dimensions has introduced the spectroscopic, site-resolved control necessary to engineer more tailored realisations of disorder. Here, we present explorations of dynamical and tunneling disorder in an atomic system by controlling laser-driven dynamics of atomic population in a momentum-space lattice. By applying static tunnelling phase disorder to a one-dimensional lattice, we observe ballistic quantum spreading. When the applied disorder fluctuates on time scales comparable to intersite tunnelling, we instead observe diffusive atomic transport, signalling a crossover from quantum to classical expansion dynamics. We compare these observations to the case of static site-energy disorder, where we directly observe quantum localisation.

Correlated Dynamics in a Synthetic Lattice of Momentum States

“…Interacting gases, combined with engineered MSLs having arbitrary and time-fluctuating disorder [11], should also enable highly controllable explorations into the physics of manybody localization [49,50]. For both scenarios, the most interesting open questions relate to phenomena driven by quantum fluctuations, which are not captured by Eq.…”

“…Here, nearest-neighbor tunneling elements are controlled through the amplitude and phase of individual frequency components of the Bragg laser field, which drive first-order, two-photon Bragg transitions [20]. Similarly, an effective potential landscape of site energies ε n is controlled by small frequency detunings of the laser fields from Bragg resonances.While there have been several demonstrations [8][9][10][11] of the ability to engineer diverse single-particle Hamiltonians using MSLs, the prospects for studying interactions and correlated dynamics have not yet been examined. In typical real-space atomic quantum simulations, two-body contact interactions are the dominant mechanism leading to correlated behavior [21].…”

“…While there have been several demonstrations [8][9][10][11] of the ability to engineer diverse single-particle Hamiltonians using MSLs, the prospects for studying interactions and correlated dynamics have not yet been examined. In typical real-space atomic quantum simulations, two-body contact interactions are the dominant mechanism leading to correlated behavior [21].…”

“…There has been recent interest in extending quantum simulation studies from real-space potentials to synthetic lattice systems composed of discrete internal [3,4] or external [5] states. These synthetic dimensions enable many unique capabilities for quantum simulation, including new approaches to engineering nontrivial topology [4,6], access to higher dimensions [3], and potential insensitivity to finite motional temperature.The recent development of momentum-space lattices (MSLs), based on the use of discrete momentum states as effective sites, has introduced a fully synthetic approach to simulating lattice dynamics [7][8][9][10][11]. As compared to partially synthetic systems [12,13], fully synthetic lattices offer complete microscopic control of system parameters.…”

“…The recent development of momentum-space lattices (MSLs), based on the use of discrete momentum states as effective sites, has introduced a fully synthetic approach to simulating lattice dynamics [7][8][9][10][11]. As compared to partially synthetic systems [12,13], fully synthetic lattices offer complete microscopic control of system parameters.…”