In this work, we investigate discrete-time transport in a generic U(1)-symmetric disordered model tuned across an array of different dynamical regimes. We develop an aggregate quantity, a circular statistical moment, which is a simple function of the magnetization profile and which elegantly captures transport properties of the system. From this quantity, we extract transport exponents, revealing behaviors across the phase diagram consistent with localized, diffusive, and—most interestingly for a disordered system—superdiffusive regimes. Investigation of this superdiffusive regime reveals the existence of a prethermal “swappy” regime unique to discrete-time systems in which excitations propagate coherently; even in the presence of strong disorder.

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Nature

Researchers investigate transport phenomena in disordered U(1)-symmetric quantum circuits across different dynamical regimes. They introduce a circular statistical moment derived from magnetization profiles to characterize transport properties, revealing localized, diffusive, and superdiffusive behaviors. The study identifies a prethermal "swappy" regime unique to discrete-time systems where quantum excitations propagate coherently despite strong disorder, challenging conventional understanding of disordered quantum systems.

Anomalous transport in U(1)-symmetric quantum circuits