AI 中文总结
本文提出双方案例的广义因果性原理，为受单次相互作用约束的量子及超量子理论提供基本限制，并给出推导广义因果约束的通用框架。
AI 中文摘要
无信号原理是涉及类空分离方的贝尔型实验的核心。尽管并非所有无信号关联都能在量子理论中实现，但无信号原理本身即使在超量子理论中也是基础的，因为违反它将意味着超光速信号传递。本着贝尔不等式设备无关性的精神，近年来人们对因果不等式产生了日益增长的兴趣，这些不等式识别出无法给出因果解释的关联。此类关联已在过程矩阵形式中得到了严格研究，该形式建立在一个类似于贝尔场景中类空分离的约束之上。我们将此约束称为单次相互作用约束，即每一方仅与环境相互作用一次。尽管付出了大量努力，目前尚无已知的基本指导原理来刻画此约束对过程矩阵生成的关联所施加的限制。在本工作中，我们通过提出双方案例的广义因果性原理来填补这一空白。我们表明，在某些情况下，广义因果性原理定义了所有信号关联集合的一个严格子集。因此，该原理为受单次相互作用约束的量子甚至超量子理论提供了基本限制。与无信号原理（其违反排除了各方之间的某些因果结构）类似，广义因果性原理的违反排除了相应的一类因果结构（具有单次相互作用约束的因果结构）。更广泛地，我们的技术为推导广义因果约束提供了一个通用框架，适用于一大类不定因果序场景。
英文摘要
The no-signalling principle lies at the heart of Bell-type experiments involving spacelike-separated parties. Although not all no-signalling correlations can be realized within quantum theory, the no-sinalling principle itself remains fundamental even for post-quantum theories, since its violation would imply superluminal signalling. In the spirit of device independent nature of the Bell inequalities, there has recently been growing interest in causal inequalities, which identify correlations admitting no causal explanation. Such correlations have been rigorously studied within the process-matrix formalism, which is built upon a constraint analogous to spacelike separation in Bell scenarios. We refer to this constraint as the single-interaction constraint, whereby each party interacts with the environment only once. Despite considerable effort, no fundamental guiding principle is currently known that characterizes the restrictions this constraint imposes on the correlations generated by Process Matrices. In this work, we address this gap by proposing a generalized causality principle for the bipartite case. We show that for certain cases, the generalised causality principle defines a strict subset of the set of all signalling correlations. This principle thus provides a fundamental limit on quantum and even post-quantum theories subject to the single-interaction constraint. By analogy with no-signalling, whose violation excludes certain causal structures among the parties, a violation of the generalised causality principle rules out a corresponding class of causal structures(causal structures with the single interaction constraint). More broadly, our techniques provide a general framework for deriving generalised causal constraints, applicable to a wide class of indefinite-causal-order scenarios.
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