论文标题
在该过程完成之前见证因果命令的叠加
Witnessing superpositions of causal orders before the process is completed
论文作者
论文摘要
我们在这封信中提出的问题如下：一个时间点上量子状态的最一般表示是什么？我们可以将当前的形式主义调整到量子操作顺序连贯或不连贯的情况下吗？如果是这样，在给定时间和事件之前和之后的事件顺序之间的状态之间的关系是什么？建立两国矢量形式主义与伪密度运算符之间的关系，我们介绍了单个伪国家的概念。通过理想或弱测量值，单时间伪态的断层造影结构是可能的。我们证明，从弱测量结果获得的特征谱使我们能够区分在过程完成之前和后选择的系统中因果阶的某些连贯和不相互的叠加。最后，我们讨论了现有光子设置中的一些可能的实验实现。
The questions we raise in this letter are as follows: What is the most general representation of a quantum state at a single point in time? Can we adapt the current formalisms to situations where the order of quantum operations is coherently or incoherently superposed? If so, what are the relations between the state at a given time and the uncertainty in the order of events before and after it? Establishing the relationship between two-state vector formalism and pseudo-density operators, we introduce the notion of a single-time pseudo-state. The tomographic construction of single-time pseudo-states is possible by ideal or weak measurements. We demonstrate that the eigenspectrum obtained from weak measurements enables us to discriminate between some coherent and incoherent superpositions of causal orders in pre- and post-selected systems before the process is completed. Finally, we discuss some possible experimental realizations in existing photonic setups.
