Enhancement of non-equilibrium thermal quantum discord and entanglement of a three-spin XX chain by multi-spin interaction and external magnetic field

TL;DR

This paper studies how multi-spin interactions and magnetic fields can enhance quantum discord and entanglement in a three-spin XX chain under non-equilibrium conditions, revealing control mechanisms for quantum correlations.

Contribution

It demonstrates that large magnetic fields and multi-spin interactions can always generate steady-state quantum discord and entanglement in a three-spin chain.

Findings

Quantum discord and entanglement are enhanced by strong multi-spin interactions.

Large magnetic fields create energy gaps that facilitate quantum correlation creation.

Steady-state quantum correlations can be controlled via system parameters.

Abstract

We investigate the non-equilibrium thermal quantum discord and entanglement of a three-spin chain whose two end spins are respectively coupled to two thermal reservoirs at different temperatures. In the three-spin chain, besides the XX-type nearest-neighbor two-spin interaction, a multi-spin interaction is also considered and a homogenous magnetic field is applied to each spin. We show that the extreme steady-state quantum discord and entanglement of the two end spins can always be created by holding both a large magnetic field and a strong multi-spin interaction. The results are explained by the thermal excitation depression due to switching a large energy gap between the ground state and the first excited state. The present investigation may provide a useful approach to control coupling between a quantum system and its environment.