Entanglement in flavored scalar scattering

TL;DR

This paper explores how quantum entanglement arises and evolves in high-energy scalar particle scattering with internal flavor quantum numbers, analyzing the effects of different couplings on entanglement transfer and generation.

Contribution

It introduces a detailed 1-loop perturbative framework to study entanglement in scalar scattering, linking unitarity and the optical theorem to entanglement dynamics.

Findings

Identifies couplings that generate or destroy entanglement.

Analyzes entanglement between momentum and flavor degrees.

Provides a formalism connecting scattering amplitudes to entanglement.

Abstract

We investigate quantum entanglement in high-energy $2\to 2$ scalar scattering, where the scalars are characterized by an internal flavor quantum number acting like a qubit. Working at the 1-loop order in perturbation theory, we build the final-state density matrix as a function of the scattering amplitudes connecting the initial to the outgoing state. In this construction, the unitarity of the $S$-matrix is guaranteed at the required order by the optical theorem. We consider the post-scattering entanglement between the momentum and flavor degrees of freedom of the final-state particles, as well as the entanglement of the two-qubit flavor subsystem. In each case we identify the couplings of the scalar potential that can generate, destroy, or transfer entanglement between different bipartite subspaces of the Hilbert space.