2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/171079In this work, I consider the effect of the unavoidable presence of soft-photons on the spin entanglement of charged qubits, arguing that the spin entanglement is not modified if we consider the effects of the infrared structure of QED on it.Master Thesis defended at Universidad Complutense de Madrid (Spain) on September, 2008. Version 3: some misprints correctedQuantum Physicstext