When Recall Fails, Discord Remembers: A Quantum Analogue of Kuhn's Theorem

Abstract

A behavioral quantum strategy is shown to replicate the payoff of a classical mixed strategy in an extensive-form game with imperfect recall, using only local measurements on a separable quantum state with zero entanglement and nonzero discord. Classical behavioral strategies, constrained by imperfect recall, cannot achieve this coordination. The result suggests a quantum analogue to Kuhn's classical equivalence: discord enables behavioral-style strategies to functionally substitute for strategic memory and recover coordination lost in the classical setting. This highlights quantum discord as a minimal and robust resource for extending bounded rationality beyond classical limits.