Double interval entanglement in quasiparticle excited states

TL;DR

This paper studies double-interval entanglement in quasiparticle excited states across various systems, introducing an efficient algorithm and revealing a universal additivity property at large momentum differences.

Contribution

Develops an algorithm for calculating entanglement measures from non-orthonormal bases and uncovers a universal additivity property in quasiparticle states.

Findings

Entanglement measures become additive at large momentum differences.

Classical limit is recovered when all momentum differences are large.

The algorithm simplifies numerical calculations of entanglement in complex systems.

Abstract

We investigate double-interval entanglement measures, specifically reflected entropy, mutual information, and logarithmic negativity, in quasiparticle excited states for classical, bosonic, and fermionic systems. We develop an algorithm that efficiently calculates these measures from density matrices expressed in a non-orthonormal basis, enabling straightforward numerical implementation. We find a universal additivity property that emerges at large momentum differences, where the entanglement measures for states with distinct quasiparticle sets equal the sum of their individual contributions. The classical limit arises as a special case of this additivity, with both bosonic and fermionic results converging to classical behavior when all momentum differences are large.