Decoherence wave in magnetic systems and creation of N\'eel antiferromagnetic state by measurement

TL;DR

This paper investigates how local measurements can induce decoherence waves and Neel antiferromagnetic order in a one-dimensional quantum spin system, linking measurement effects to magnetic state formation.

Contribution

It demonstrates that measurements can create Neel order from a singlet ground state in finite antiferromagnetic chains, highlighting the role of anisotropy.

Findings

Measurement induces decoherence waves in magnetic sublattices.

Symmetry breaking anisotropy does not align spins.

Easy-axis anisotropy enables Neel order formation.

Abstract

The interplay between the singlet ground state of the antiferromagnetic Heisenberg model and the experimentally measured N\'eel state of antiferromagnets is studied. To verify the hypothesis [M. I. Katsnelson et al., Phys. Rev. B 63, 212404 (2001)] that the latter can be considered to be a result of local measurements destroying the entanglement of the quantum ground state, we have performed systematic simulations of the effects of von Neumannmeasurements for the case of a one-dimensional antiferromagnetic spin-1/2 system for various types and degrees of magnetic anisotropies. It is found that in the ground state, a magnetization measurement can create decoherence waves [M. I. Katsnelson et al. Phys. Rev. A 62, 022118 (2000)] in the magnetic sublattices, and that a symmetry breaking anisotropy does not lead to alignment of the spins in a particular direction. However, for an easy-axis anisotropy of the same order magnitude as the exchange constant, a measurement on the singlet ground state can create N\'eel-ordering in finite systems of experimentally accessible size.