Characterizing entanglement dynamics in QED scattering processes

TL;DR

This paper analyzes how entanglement evolves in QED scattering processes, revealing that maximal initial entanglement is preserved and fixed points tend to be asymptotic maximally entangled states, influenced by symmetries.

Contribution

It introduces a quantum map framework to characterize entanglement dynamics in QED scattering, including fermions and photons, based on spectral properties and symmetries.

Findings

Maximal initial entanglement is always preserved in fermion-only scattering.

Iterated quantum maps lead to asymptotic maximally entangled states.

Map properties are rooted in discrete symmetries of QED interactions.

Abstract

We study entanglement dynamics among helicity degrees of freedom in quantum electrodynamics (QED) scattering processes. For generic initial states, we consider scattering at fixed momentum, corresponding to a generalized measurement described by a positive operator-valued measure, resulting in a post-measurement state. Such processes are modeled in terms of quantum maps, whose spectral structure fully determines the associated entanglement dynamics. For scattering involving fermions only, maximal entanglement present in the initial state is always preserved. Moreover, iterating the corresponding quantum maps on arbitrary initial states, we obtain the fixed points of the maps, which, in the largest number of cases, are asymptotic (pure) maximally entangled states. The structure of the maps also accounts for the entanglement dynamics in processes involving both fermions and photons. The defining properties of these maps originate from discrete symmetries of the QED interaction.