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 quasisolvability of the convex roof, we concentrate on a four-site model Hamiltonian. This leads to a picture of fixed decomposition states through which the optimal decomposition brachiates. In general, the field, and hence, 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 plateau 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 nonzero angle $\alpha$ of the magnetic field to transversality. This system could be experimentally used as a quasipure source of threetangled states or as an entanglement triggered switch depending on the experimental error in the field orientation.

Close

PrevNext

View figure in article

• Magnetism
• Quantum correlations in quantum information
• Quantum correlations, foundations & formalism
• Quantum information theory