Robustness of Aharonov-Bohm cages in quantum walks

It was recently shown that Aharonov-Bohm (AB) cages exist for quantum walks (QW) on certain tilings—such as the diamond chain or the dice (or T 3) lattice—for a proper choice of coins. In this article, we probe the robustness of these AB cages to various perturbations. When the cages are destroyed, we analyze the leakage mechanism and characterize the resulting dynamics. Quenched disorder typically breaks the cages and leads to an exponential decay of the wave function similar to Anderson localization. Dynamical disorder or repeated measurements destroy phase coherence and turn the QW into a classical random walk with diffusive behavior. Combining static and dynamical disorder in a specific way leads to subdiffusion with an anomalous exponent controlled by the quenched disorder distribution. Introducing interaction to a second walker can also break the cages and restore a ballistic motion for a “molecular” bound state.