论文标题
不可能的测量需要不可能的设备
Impossible measurements require impossible apparatus
论文作者
论文摘要
相对论量子场理论中公认的开放概念问题涉及测量与因果关系之间的关系。量子测量规则的幼稚概括可以允许超亮信号传导（“不可能的测量”）。这引发了描述物理允许量子测量和操作的问题。我们在最近提出的框架中分析了此问题，在该框架中，通过将系统与探针耦合通过将局部测量（可能是弯曲的时空）进行物理描述。我们表明，如果系统和探测之间的耦合是本地的，则此设置中的状态更新规则与因果关系一致。因此，通过建立一个定义明确的连续测量框架，我们还提供了一类物理允许的操作。相反，只能使用不可能的（非本地）设备进行不可能的测量。
A well-recognised open conceptual problem in relativistic quantum field theory concerns the relation between measurement and causality. Naive generalisations of quantum measurement rules can allow for superluminal signalling ('impossible measurements'). This raises the problem of delineating physically allowed quantum measurements and operations. We analyse this issue in a recently proposed framework in which local measurements (in possibly curved spacetime) are described physically by coupling the system to a probe. We show that the state-update rule in this setting is consistent with causality provided that the coupling between the system and probe is local. Thus, by establishing a well-defined framework for successive measurements, we also provide a class of physically allowed operations. Conversely, impossible measurements can only be performed using impossible (non-local) apparatus.
