2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/128008We show how to quantify the optimal tradeoff between the amount of information retrieved by a quantum measurement in estimating an unknown spin coherent state and the disturbance on the state itself, and how to derive the corresponding minimum-disturbing measurement.6 pages, 3 figures; improved introduction, simplified notation, and new references. To appear on Phys. Rev. AQuantum Physicstext