Emergence of steady quantum transport in a superconducting processor

TL;DR

This paper demonstrates the emergence of steady non-equilibrium quantum transport in a superconducting processor, showing how macroscopic steady currents arise and can be controlled in a quantum system, providing insights into quantum thermodynamics.

Contribution

It introduces a novel experimental platform using superconducting qubits to emulate baths and observe steady quantum transport, advancing understanding of non-equilibrium quantum physics.

Findings

Steady particle currents are independent of initial bath states.

Currents' fluctuations decrease with bath size, mimicking thermodynamic baths.

Steady currents can be tuned by manipulating bath properties.

Abstract

Non-equilibrium quantum transport is crucial to technological advances ranging from nanoelectronics to thermal management. In essence, it deals with the coherent transfer of energy and (quasi-)particles through quantum channels between thermodynamic baths. A complete understanding of quantum transport thus requires the ability to simulate and probe macroscopic and microscopic physics on equal footing. Using a superconducting quantum processor, we demonstrate the emergence of non-equilibrium steady quantum transport by emulating the baths with qubit ladders and realising steady particle currents between the baths. We experimentally show that the currents are independent of the microscopic details of bath initialisation, and their temporal fluctuations decrease rapidly with the size of the baths, emulating those predicted by thermodynamic baths. The above characteristics are experimental evidence of pure-state statistical mechanics and prethermalisation in non-equilibrium many-body quantum systems. Furthermore, by utilising precise controls and measurements with single-site resolution, we demonstrate the capability to tune steady currents by manipulating the macroscopic properties of the baths, including filling and spectral properties. Our investigation paves the way for a new generation of experimental exploration of non-equilibrium quantum transport in strongly correlated quantum matter.