发表机构
Perimeter Institute for Theoretical Physics; Department of Physics and Astronomy, University of Waterloo; Institute for Quantum Computing, University of Waterloo（Perimeter Institute for Theoretical Physics; 滑铁卢大学物理与天文系; 滑铁卢大学量子计算研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究探讨广义语境性在量子密钥分发中的作用，证明其对正密钥率必要但不充分，并展示操作等价关系可提升渐近密钥率。
AI 中文摘要
贝尔非定域性允许在不信任设备内部操作的情况下认证密钥，甚至能抵御仅受无信号原理约束的窃听者。我们探讨广义语境性（一种在单系统制备-测量实验中可用的非经典性概念）是否能发挥类似作用。在我们的方法中，Alice和Bob首先在其局部制备和测量程序之间建立操作等价关系，这些关系随后被视为理论无关的约束，任何对通信信道的物理干预（包括对手的干预）都必须遵守这些约束。Eve在其他方面不受限制，即她对传输系统的干预不被假设由量子理论描述。在此对抗模型中，我们证明Eve针对个体攻击的最优猜测概率是有限线性规划的解，因此最坏情况下的渐近密钥率仅由观测统计量和操作等价关系得出。我们证明语境性对于正密钥率是必要的。然而，我们也表明它并不充分。具体而言，已知能对抗量子窃听者产生秘密密钥的(3,2)-奇偶性遗忘随机访问码，在对抗后量子窃听者时无法产生任何可认证的密钥率。相反，在无信号约束中没有对应物的操作等价关系可以严格增加渐近密钥率。我们通过标准CHSH协议的制备-测量版本（具有对齐的密钥生成设置）来说明这一点。
英文摘要
Bell nonlocality allows secret key to be certified without trusting the internal operation of the devices, and even against eavesdroppers constrained only by the no-signaling principle. We ask whether generalized contextuality, a notion of nonclassicality available in prepare-and-measure experiments on a single system, can play an analogous role. In our approach, Alice and Bob first establish operational equivalences among their local preparation and measurement procedures, which are then treated as theory-independent constraints that any physical intervention on the communication channel, including that of an adversary, must respect. Eve is otherwise unrestricted, that is, her intervention on the transmitted system is not assumed to be described by quantum theory. Within this adversarial model, we show that Eve's optimal guessing probability against individual attacks is the solution of a finite linear program, and hence that a worst-case asymptotic key rate follows from the observed statistics and the operational equivalences alone. We prove that contextuality is necessary for a positive key rate. However, we also show that it is not sufficient. Concretely, the (3,2)-parity-oblivious random access code, known to yield secret key against a quantum eavesdropper, yields none certifiable key rate against a post-quantum one. Conversely, operational equivalences with no analogue among no-signaling constraints can strictly increase the asymptotic key rate. We illustrate this with the prepare-and-measure version of the standard CHSH protocol with an aligned key-generating setting.
Comments9+7 pages, 5 figures. Comments are welcome!
