Enhanced violation of a Leggett-Garg inequality under nonequilibrium thermal conditions

TL;DR

This paper demonstrates that nonequilibrium thermal conditions can enhance violations of the Leggett-Garg inequality in quantum systems, revealing new insights into quantum correlations under thermal gradients.

Contribution

It provides analytical and numerical evidence that heat currents in nonequilibrium conditions can increase LGI violations, with a detailed Kraus operator analysis.

Findings

LGI violations are enhanced under nonequilibrium thermal conditions.

Power law relations link dissipation strength and temperature at violation boundaries.

Spatial and temporal correlation inequalities remain connected in nonequilibrium settings.

Abstract

We investigate both analytically and numerically violations of a Leggett-Garg inequality (LGI) for a composite quantum system in contact with two separate reservoirs at different temperatures. Remarkably we find that LGI violations can be enhanced when a heat current is established at low temperatures in a steady-state regime. Based on a Kraus operator decomposition of the non-unitary evolution for a system formed by two interacting spins or quantum bits, we provide analytical support for power law relations between dissipation strength and mean temperature in the borderlines separating parameter regions where non-equilibrium conditions affect differently the maximal LGI violation. Furthermore, a correspondence between spatial and temporal correlation inequalities is shown to persist even in such nonequilibrium thermal settings.