Decoherence and pointer states in small antiferromagnets: A benchmark test

TL;DR

This paper investigates the decoherence process in a small antiferromagnetic system coupled to an environment, identifying exact pointer states and analyzing their robustness and dynamics near quantum measurement limits.

Contribution

It provides an exact identification of pointer states in a small antiferromagnet and examines their robustness and the influence of the system's self-Hamiltonian on decoherence.

Findings

Identified two exact pointer states in the antiferromagnet.

Quantified robustness of states using entropy measures.

Showed the system's self-Hamiltonian can dominate near quantum measurement conditions.

Abstract

We study the decoherence process of a four spin-1/2 antiferromagnet that is coupled to an environment of spin-1/2 particles. The preferred basis of the antiferromagnet is discussed in two limiting cases and we identify two $\it{exact}$ pointer states. Decoherence near the two limits is examined whereby entropy is used to quantify the $\it{robustness}$ of states against environmental coupling. We find that close to the quantum measurement limit, the self-Hamiltonian of the system of interest can become dynamically relevant on macroscopic timescales. We illustrate this point by explicitly constructing a state that is more robust than (generic) states diagonal in the system-environment interaction Hamiltonian.