论文标题
不确定时间方向的量子操作
Quantum operations with indefinite time direction
论文作者
论文摘要
相对于时间的箭头，量子颗粒的基本动力学是中性的。但是，我们的实验并不是：我们观察到量子系统从过去发展到未来，而不是相反。一个基本的问题是，是否有可能构想一组更广泛的操作，从未来到过去，或更一般地，向前和向后方向探测向后方向的量子过程。在这里，我们介绍了这些操作的数学框架，表明其中一些不能解释为探测朝着确定方向进行处理的操作混合物。作为一个具体的示例，我们构建了一个称为量子时间翻转的操作，该操作在向前和后向方向的量子叠加中探测未知动力学。该操作比所有操作都具有明确的方向表现出信息理论优势。可以使用量子传送概率地实现它，并可以通过光子系统实验重现。更普遍地，我们介绍了一组多方操作，其中包括不确定的时间方向以及不确定的因果秩序，为量子理论的潜在扩展提供了一个框架。
The fundamental dynamics of quantum particles is neutral with respect to the arrow of time. And yet, our experiments are not: we observe quantum systems evolving from the past to the future, but not the other way round. A fundamental question is whether it is possible to conceive a broader set of operations that probe quantum processes in the backward direction, from the future to the past, or more generally, in a combination of the forward and backward directions. Here we introduce a mathematical framework for these operations, showing that some of them cannot be interpreted as random mixtures of operations that probe processes in a definite direction. As a concrete example, we construct an operation, called the quantum time flip, that probes an unknown dynamics in a quantum superposition of the forward and backward directions. This operation exhibits an information-theoretic advantage over all operations with definite direction. It can be realised probabilistically using quantum teleportation, and can be reproduced experimentally with photonic systems. More generally, we introduce a set of multipartite operations that include indefinite time direction as well as indefinite causal order, providing a framework for potential extensions of quantum theory.
