Kujala Janne V, Dzhafarov Ehtibar N
Department of Mathematics and Statistics, University of Turku, FI-20014 Turun yliopisto, Finland.
Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907, USA.
Entropy (Basel). 2023 Sep 20;25(9):1356. doi: 10.3390/e25091356.
Counterfactual definiteness (CFD) means that if some property is measured in some context, then the outcome of the measurement would have been the same had this property been measured in a different context. A context includes all other measurements made together with the one in question, and the spatiotemporal relations among them. The proviso for CFD is non-disturbance: any physical influence of the contexts on the property being measured is excluded by the laws of nature, so that no one measuring this property has a way of ascertaining its context. It is usually claimed that in quantum mechanics CFD does not hold, because if one assigns the same value to a property in all contexts it is measured in, one runs into a logical contradiction, or at least contravenes quantum theory and experimental evidence. We show that this claim is not substantiated if one takes into account that only one of the possible contexts can be a factual context, all other contexts being counterfactual. With this in mind, any system of random variables can be viewed as satisfying CFD. The concept of CFD is closely related to but distinct from that of noncontextuality, and it is the latter property that may or may not hold for a system, in particular being contravened by some quantum systems.
反事实确定性（CFD）意味着，如果在某种情境下测量某个属性，那么如果在不同情境下测量该属性，测量结果将会是相同的。一种情境包括与所讨论的测量一起进行的所有其他测量，以及它们之间的时空关系。CFD的前提是无干扰：情境对被测量属性的任何物理影响都被自然法则排除，因此测量该属性的任何人都无法确定其情境。通常认为在量子力学中CFD不成立，因为如果在所有测量该属性的情境中都赋予其相同的值，就会陷入逻辑矛盾，或者至少违反量子理论和实验证据。我们表明，如果考虑到只有一种可能的情境可以是事实性情境，所有其他情境都是反事实的，那么这种说法是没有根据的。考虑到这一点，任何随机变量系统都可以被视为满足CFD。CFD的概念与非情境性概念密切相关但又有所不同，正是后一种属性对于一个系统可能成立也可能不成立，特别是一些量子系统会违反它。
