Double interval entanglement in quasiparticle excited states (opens in new tab)

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...