Emergence of Navier-Stokes hydrodynamics in chaotic quantum circuits

TL;DR

This paper demonstrates that chaotic two-dimensional quantum circuits with conserved currents exhibit hydrodynamics described by Navier-Stokes equations, enabling efficient computation of their viscosity.

Contribution

It constructs a family of nonintegrable quantum circuits that connect quantum chaos with classical hydrodynamics, providing a method to compute transport coefficients like viscosity.

Findings

Circuit-averaged transport coefficients match typical circuit values.

Hydrodynamics of these quantum systems is governed by Navier-Stokes equations.

Viscosity can be efficiently computed via classical Markov processes.

Abstract

We construct an ensemble of two-dimensional nonintegrable quantum circuits that are chaotic but have a conserved particle current, and thus a finite Drude weight. The long-wavelength hydrodynamics of such systems is given by the incompressible Navier-Stokes equations. By analyzing circuit-to-circuit fluctuations in the ensemble we argue that these are negligible, so the circuit-averaged value of transport coefficients like the viscosity is also (in the long-time limit) the value in a typical circuit. The circuit-averaged transport coefficients can be mapped onto a classical irreversible Markov process. Therefore, remarkably, our construction allows us to efficiently compute the viscosity of a family of strongly interacting chaotic two-dimensional quantum systems.