论文标题
违反时间范围的子系统违反因果不平等的过程的存在
Existence of processes violating causal inequalities on time-delocalised subsystems
论文作者
论文摘要
已经表明，从理论上讲，存在量子和经典过程，在这种量子和经典过程中，不同政党执行的操作不会以明确的因果秩序发生。一个核心问题是在实践中是否可以以及如何实现此类过程。为了为某些此类过程在标准量子理论中实现的观念提供严格的论点，已经引入了时间迁移量子子系统的概念。在本文中，我们表明，对于三方过程的所有统一延伸，存在时间范围的子系统的实现。值得注意的是，该类包含违反因果不平等的过程，即可以产生相关性，以与设备无关的方式见证与确定的因果秩序的不相容性。我们考虑了具有单一延伸的三方经典过程的一个已知醒目的例子，并研究了其在时间范围的子系统上的实现。然后，我们讨论了在这种情况下违反因果不平等意味着什么的问题，并认为表明所关注的变量之间没有明确的因果秩序，这确实是一个有意义的概念。
It has been shown that it is theoretically possible for there to exist quantum and classical processes in which the operations performed by separate parties do not occur in a well-defined causal order. A central question is whether and how such processes can be realised in practice. In order to provide a rigorous argument for the notion that certain such processes have a realisation in standard quantum theory, the concept of time-delocalised quantum subsystem has been introduced. In this paper, we show that realisations on time-delocalised subsystems exist for all unitary extensions of tripartite processes. Remarkably, this class contains processes that violate causal inequalities, i.e., that can generate correlations that witness the incompatibility with definite causal order in a device-independent manner. We consider a known striking example of such a tripartite classical process that has a unitary extension, and study its realisation on time-delocalised subsystems. We then discuss the question of what a violation of causal inequalities implies in this setting, and argue that it is indeed a meaningful concept to show the absence of a definite causal order between the variables of interest.
