2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/161208We analytically and numerically study the effects of pulsed control on the decoherence of a qubit coupled to a quantum spin bath. When the environment is critical, decoherence is faster and we show that the control is relatively more effective. Two coupling models are investigated, namely a qubit coupled to a bath via a single link and a spin star model, yielding results that are similar and consistent.10 pages, 4 figures, replaced with published versionQuantum Physicstext