The notorious Wigner’s friend thought experiment (and modifications thereof) has received renewed interest especially due to new arguments that force us to question some of the fundamental assumptions of quantum theory. In this paper, we formulate a no-go theorem for the persistent reality of Wigner’s friend’s perception, which allows us to conclude that the perceptions that the friend has of her own measurement outcomes at different times cannot “share the same reality”, if seemingly natural quantum mechanical assumptions are met. More formally, this means that, in a Wigner’s friend scenario, there is no joint probability distribution for the friend’s perceived measurement outcomes at two different times, that depends linearly on the initial state of the measured system and whose marginals reproduce the predictions of unitary quantum theory. This theorem entails that one must either (1) propose a nonlinear modification of the Born rule for two-time predictions, (2) sometimes prohibit the use of present information to predict the future—thereby reducing the predictive power of quantum theory—or (3) deny that unitary quantum mechanics makes valid single-time predictions for all observers. We briefly discuss which of the theorem’s assumptions are more likely to be dropped within various popular interpretations of quantum mechanics.

臭名昭著的维格纳的朋友思想实验（及其修改）引起了新的兴趣，特别是由于新的论点迫使我们质疑量子理论的一些基本假设。在本文中，我们为维格纳朋友的感知的持久现实制定了一个不通过定理，这使我们可以得出结论：如果朋友似乎在不同时间拥有自己的测量结果，这种感知就无法“共享相同的现实”。满足自然量子力学假设。更正式地讲，这意味着，在维格纳的朋友场景中，朋友在两个不同的时间感知到的测量结果没有联合概率分布，线性分布取决于被测系统的初始状态，其边际重现了单位量子的预测。理论。该定理要求一个人必须（1）对两次预测的Born规则提出非线性修改，（2）有时禁止使用当前信息来预测未来，从而降低了量子理论的预测能力，或者（ 3）否认quantum量子力学为所有观察者做出有效的单次预测。我们简要讨论了该定理的哪些假设更可能被量子力学的各种流行解释所抛弃。