We introduce a new framework for quantum channel discrimination in an adversarial setting, where the tester plays against an adversary. We show that in asymmetric hypothesis testing, the optimal type-II error exponent is precisely characterized by a new notion of quantum channel divergence (termed the minimum output channel divergence). This serves as a direct analog of the quantum Stein's lemma in this new framework, and complements previous studies on ``best-case'' channel discrimination, thereby providing a complete understanding of the ultimate limits of quantum channel discrimination. Notably, the optimal error exponent can be achieved by simple non-adaptive adversarial strategies, and despite the need for regularization, it remains efficiently computable and satisfies the strong converse property in general. Furthermore, we show that entropy accumulation, a powerful tool in quantum cryptography, can be reframed as an adversarial channel discrimination problem, establishing a new connection between quantum information theory and quantum cryptography.

翻译：我们提出了一种对抗性场景下的量子信道鉴别新框架，其中测试者与对手进行博弈。我们证明，在非对称假设检验中，最优第二类错误指数可由一种新的量子信道散度概念（称为最小输出信道散度）精确刻画。这构成了该新框架中量子斯坦引理的直接类比，并补充了先前关于“最佳情况”信道鉴别的研究，从而为量子信道鉴别的终极极限提供了完整理解。值得注意的是，最优错误指数可通过简单的非自适应对抗策略实现，且尽管需要正则化处理，该指数仍保持高效可计算性，并普遍满足强逆性质。此外，我们证明量子密码学中的强大工具——熵累积——可被重新表述为对抗性信道鉴别问题，从而在量子信息论与量子密码学之间建立了新的联系。