Threetangle in the XY-model class with a non-integrable field background

TL;DR

This paper investigates the behavior of the threetangle, an entanglement measure, in a non-integrable XY-model with an in-plane field, revealing conditions under which finite entanglement persists despite integrability breaking.

Contribution

It provides the first analysis of the threetangle in a non-integrable XY-model with an in-plane field, highlighting regimes where entanglement remains robust.

Findings

Finite threetangle observed near specific field strengths.

Weak inhomogeneity allows for stable entanglement.

Potential for experimental entanglement sources or switches.

Abstract

The square root of the threetangle is calculated for the transverse XY-model with an integrability-breaking in-plane field component. To be in a regime of quasi-solvability of the convex roof, here we concentrate here on a 4-site model Hamiltonian. In general, the field and hence a mixing of the odd/even sectors, has a detrimental effect on the threetangle, as expected. Only in a particular spot of models with no or weak inhomogeneity $\gamma$ does a finite value of the tangle prevail in a broad maximum region of the field strength $h\approx 0.3\pm 0.1$. There, the threetangle is basically independent of the non-zero angle $\alpha$. This system could be experimentally used as a quasi-pure source of threetangled states or as an entanglement triggered switch depending on the experimental error in the field orientation.