论文标题
时间方向的实验叠加
Experimental superposition of time directions
论文作者
论文摘要
在宏观世界中，时间本质上是不对称的，从过去到将来都朝着特定的方向流动。但是，对于量子系统而言，这不一定是正确的，因为某些量子过程在时间逆转下会产生有效的量子发展。假设可以在两个时间方向上探测此类过程，我们还可以考虑在向前和向后时间方向的连贯叠加中探测的量子过程。这比迄今为止文献中考虑的量子过程（包括无限期因果秩序的量子）产生了更广泛的量子过程。在这项工作中，我们首次演示了属于这个新类的操作：量子时间翻转。使用对此操作的光子实现，我们将其应用于两组操作员之间的歧视任务的游戏。该游戏不仅可以作为无限期方向的见证，而且还可以使用固定的时间方向，甚至是那些具有不确定因果秩序的策略的计算优势。
In the macroscopic world, time is intrinsically asymmetric, flowing in a specific direction, from past to future. However, the same is not necessarily true for quantum systems, as some quantum processes produce valid quantum evolutions under time reversal. Supposing that such processes can be probed in both time directions, we can also consider quantum processes probed in a coherent superposition of forwards and backwards time directions. This yields a broader class of quantum processes than the ones considered so far in the literature, including those with indefinite causal order. In this work, we demonstrate for the first time an operation belonging to this new class: the quantum time flip. Using a photonic realisation of this operation, we apply it to a game formulated as a discrimination task between two sets of operators. This game not only serves as a witness of an indefinite time direction, but also allows for a computational advantage over strategies using a fixed time direction, and even those with an indefinite causal order.
