Quantum correlations of two qubits interacting with a macroscopic medium

TL;DR

This paper studies how two spin-1/2 particles interacting with a 1D spin array as an environment exhibit entanglement decay and quantum discord amplification, revealing distinct dynamical behaviors and effects of environmental excitations.

Contribution

It provides an exactly solvable model analyzing the contrasting dynamics of entanglement and quantum discord in a spin environment, highlighting new phenomena.

Findings

Entanglement can undergo sudden death and birth but not increase beyond initial value.

Quantum discord can be amplified and generated through environment interaction.

Quantum discord decays asymptotically to zero and is affected by environmental excitations.

Abstract

We consider two particles of spin-1/2 interacting with a one-dimensional N-spin array, which is an exactly solvable model. The dynamics of entanglement and quantum discord (QD) of the spins of the two particles is investigated by regarding the 1D N-spin array as the environment. It is found that although the entanglement may suffers a sudden death and a sudden birth in the evolution, it can neither be generated nor become larger than its initial value. Different from the entanglement dynamics, QD can be amplified, and even be generated by the interaction between particles and the common environment. We also observe that QD decays asymptotically to zero and later experiences a rival when the average number of excitation in the 1D N-spin array becomes larger in the case of nonzero inter-distance between two particles.