Localization may survive in periodically driven (Floquet) quantum systems, but is generally unstable for aperiodic drives. In this Letter, we identify a hidden conservation law originating from a chiral symmetry in a disordered spin-12 XX chain. This protects indefinitely long-lived localization for general—even aperiodic—drives. Therefore, rather counterintuitively, adding further potential disorder which spoils the conservation law delocalizes the system, via a controllable parametrically long-lived prethermal regime. This provides an example of persistent single-particle “localization without eigenstates.”     «

Localization may survive in periodically driven (Floquet) quantum systems, but is generally unstable for aperiodic drives. In this Letter, we identify a hidden conservation law originating from a chiral symmetry in a disordered spin-12 XX chain. This protects indefinitely long-lived localization for general—even aperiodic—drives. Therefore, rather counterintuitively, adding further potential disorder which spoils the conservation law delocalizes the system, via a controllable parametrically long...     »