Zych Magdalena, Costa Fabio, Pikovski Igor, Brukner Časlav
Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, QLD, 4072, Australia.
ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, 02138, USA.
Nat Commun. 2019 Aug 21;10(1):3772. doi: 10.1038/s41467-019-11579-x.
Time has a fundamentally different character in quantum mechanics and in general relativity. In quantum theory events unfold in a fixed order while in general relativity temporal order is influenced by the distribution of matter. When matter requires a quantum description, temporal order is expected to become non-classical-a scenario beyond the scope of current theories. Here we provide a direct description of such a scenario. We consider a thought experiment with a massive body in a spatial superposition and show how it leads to entanglement of temporal orders between time-like events. This entanglement enables accomplishing a task, violation of a Bell inequality, that is impossible under local classical temporal order; it means that temporal order cannot be described by any pre-defined local variables. A classical notion of a causal structure is therefore untenable in any framework compatible with the basic principles of quantum mechanics and classical general relativity.
在量子力学和广义相对论中，时间具有本质上不同的特性。在量子理论中，事件按固定顺序展开，而在广义相对论中，时间顺序受物质分布的影响。当物质需要量子描述时，时间顺序预计会变得非经典——这是当前理论范围之外的一种情况。在这里，我们提供了对这种情况的直接描述。我们考虑一个思想实验，其中一个大质量物体处于空间叠加态，并展示它如何导致类时事件之间的时间顺序纠缠。这种纠缠使得能够完成一项任务，即违反贝尔不等式，而这在局部经典时间顺序下是不可能的；这意味着时间顺序不能由任何预先定义的局部变量来描述。因此，在任何与量子力学和经典广义相对论基本原理兼容的框架中，因果结构的经典概念都是站不住脚的。
