Magnetic shielding of quantum entanglement states

TL;DR

This paper investigates how external magnetic fields influence quantum entanglement in spin-1/2 Heisenberg systems, revealing a magnetic shielding effect where entanglement persists despite strong magnetic fields.

Contribution

It introduces a measure of thermal quantum entanglement based on Hilbert-Schmidt distance and demonstrates the magnetic shielding effect in antiferromagnetic systems.

Findings

Entanglement exists only in antiferromagnetic systems below a certain temperature.

Decoherence temperature is proportional to exchange coupling and independent of magnetic field.

Quantum entanglement can survive high magnetic fields, showing a shielding effect.

Abstract

The measure of quantum entanglement is determined for any dimer, either ferromagnetic or antiferromagnetic, spin-1/2 Heisenberg systems in the presence of external magnetic field. The physical quantity proposed as a measure of thermal quantum entanglement is the distance between states defined through the Hilbert-Schmidt norm. It has been shown that for ferromagnetic systems there is no entanglement at all. However, although under applied magnetic field, antiferromagnetic spin-1/2 dimers exhibit entanglement for temperatures below the decoherence temperature -- the one above which the entanglement vanishes. In addition to that, the decoherence temperature shows to be proportional to the exchange coupling constant and independent on the applied magnetic field, consequently, the entanglement may not be destroyed by external magnetic fields -- the phenomenon of {\it magnetic shielding effect of quantum entanglement states}. This effect is discussed for the binuclear nitrosyl iron complex [Fe$_2$(SC$_3$H$_5$N$_2$)$_2$(NO)$_4$] and it is foreseen that the quantum entanglement survives even under high magnetic fields of Tesla orders of magnitude.