论文标题
环状量子因果模型
Cyclic Quantum Causal Models
论文作者
论文摘要
因果推理对科学至关重要，但是量子理论挑战了它。违反贝尔不平等的量子相关性违背了经典因果模型框架内令人满意的因果解释。此外，预期包含量子系统和重力的理论将允许以无限期因果秩序操作的因果不可分割的过程，这根本无法因果关系。第一个挑战是通过近期基因量子因果模型的最新发展解决的，允许对量子过程的因果解释 - 只要它们承认有一定的因果秩序，即具有无环的因果结构。这项工作解决了因果关系不可分割的过程，并通过将量子因果模型扩展到环状因果结构来为它们提供因果观点。在方法的其他应用中，还表明，所有单位扩展的两部分过程都是可分离的，并且对于统一过程，其因果关系的因果关系和循环性是等效的。
Causal reasoning is essential to science, yet quantum theory challenges it. Quantum correlations violating Bell inequalities defy satisfactory causal explanations within the framework of classical causal models. What is more, a theory encompassing quantum systems and gravity is expected to allow causally nonseparable processes featuring operations in indefinite causal order, defying that events be causally ordered at all. The first challenge has been addressed through the recent development of intrinsically quantum causal models, allowing causal explanations of quantum processes -- provided they admit a definite causal order, i.e. have an acyclic causal structure. This work addresses causally nonseparable processes and offers a causal perspective on them through extending quantum causal models to cyclic causal structures. Among other applications of the approach, it is shown that all unitarily extendible bipartite processes are causally separable and that for unitary processes, causal nonseparability and cyclicity of their causal structure are equivalent.
