Quantum and classical correlations in high temperature dynamics of two coupled large spins

TL;DR

This paper analyzes the dynamics of quantum and classical correlations in two coupled large spins at high temperature, providing analytical expressions and comparing measurement methods, revealing that classical correlations dominate over quantum ones.

Contribution

It offers the first analytical expressions for mutual information and correlations in high-temperature coupled large spins, comparing POVM and von Neumann measurements.

Findings

Quantum correlations are smaller than classical correlations.

Quantum correlations decrease with increasing spin quantum numbers at short times.

Quantum correlations peak at half the quantum period.

Abstract

We study dynamical correlations of two coupled large spins depending on the time and on the spin quantum numbers. In the high-temperature approximation, we obtain analytical expressions for the mutual informations, quantum and classical parts of correlations. The latter was obtained performing the non-orthogonal projective (POVM) measurements onto the spin coherent states of two spins or one spin, as well as by means of the orthogonal projective measurement of von Neumann. Contribution from quantum correlations is much less than that from classical ones and decreasing with the increase in spin quantum numbers at short times. However, it is not so in a time equal to half of the quantum period.