Generation of quantum correlations at adiabatic demagnetization

Abstract

Adiabatic demagnetization (AD) is an effective way to achieve low temperatures required for generating quantum correlations. The emergence and behavior of quantum and classical correlations in a one-dimensional dipolar-coupled nuclear spin-1/2 system cooled using the conventional AD technique are theoretically investigated. The case is considered where the Zeeman energy is of the order of or even less than the dipolar interaction one. It is shown that, the mutual information and classical correlations increase monotonically in the AD process and achieve their maximums at switching off the magnetic field. The quantum correlations achieve the maximum at the point where the Zeeman energy is the order of the dipolar energy and decrease to zero with decreasing the field. Discord and classical correlations are asymmetrical with respect to permutation of asymmetrically located spins.