The Wigner's friend experiment is a thought experiment in which a so-called superobserver (Wigner) observes another observer (the friend) who has performed a quantum measurement on a physical system. In this setup Wigner treats the friend, the system and potentially other degrees of freedom involved in the friend's measurement as one joint quantum system. In general, Wigner's measurement changes the internal record of the friend's measurement result such that after the measurement by the superobserver the result stored in the observer's memory register is no longer the same as the result the friend obtained initially, i.e. before she was measured by Wigner. Here, we show that any awareness by the friend of this change of her memory, which can be modeled by an additional register storing the information about the change, conflicts with the no-signaling condition in extended Wigner-friend scenarios.

中文翻译：

---

维格纳朋友的记忆和无信号原则


维格纳的朋友实验是一个思想实验，其中所谓的超级观察者（维格纳）观察另一个对物理系统进行量子测量的观察者（朋友）。在这一设置中，维格纳将朋友、系统以及朋友测量中涉及的潜在其他自由度视为一个联合量子系统。一般来说，维格纳的测量改变了朋友测量结果的内部记录，使得在超级观察者测量之后，存储在观察者内存寄存器中的结果不再与朋友最初获得的结果相同，即在她被维格纳测量之前。在这里，我们表明，朋友对其记忆变化的任何意识（可以通过存储有关变化的信息的附加寄存器来建模）与扩展维格纳朋友场景中的无信号条件相冲突。