2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/88775In a recent paper, Eisert et al. presented a quantum mechanical generalization of Prisoner's Dilemma. They asserted that the maximally entangled game exhibits a unique Nash equilibrium which yields a pay-off equivalent to cooperative behaviour. In this comment we show that their observation is incorrect: there is no Nash equilibrium in the space of deterministic quantum strategies.2 pages, 1 figure. Please address correspondence to s.benjamin@qubit.orgQuantum Physicstext