In his 1935 Gedankenexperiment, Erwin Schrödinger imagined a box with a cat and a poisonous substance which has a 50% probability of being released, based on the decay of a radioactive atom. As such, the life of the cat and the state of the poison become entangled, and the fate of the cat is determined upon opening the box. We present an experimental technique that keeps the cat alive on any account. This method relies on the time-resolved Hong–Ou–Mandel effect: two long, identical photons impinging on a beam splitter always bunch in either of the outputs. Interpreting the first photon detection as the state of the poison, the second photon is identified as the state of the cat. Even after the collapse of the first photon’s state, we show their fates are intertwined through quantum interference. We demonstrate this by a sudden phase change between the inputs, administered conditionally on the outcome of the first detection, which steers the second photon to a pre-defined output and ensures that the cat is always observed alive.

中文翻译：

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如何给薛定谔的猫服用解毒剂

在他 1935 年的 Gedanken 实验中，Erwin Schrödinger 想象了一个盒子，里面有一只猫和一种有毒物质，根据放射性原子的衰变，这种物质有 50% 的概率被释放。就这样，猫的性命和毒的状态纠缠在一起，猫的命运一开箱就决定了。我们提出了一种无论如何都能让猫活着的实验技术。这种方法依赖于时间分辨的 Hong-Ou-Mandel 效应：撞击在分束器上的两个相同的长光子总是在任一输出中聚集。将第一个光子检测解释为毒物的状态，第二个光子被识别为猫的状态。即使在第一个光子状态崩溃之后，我们也表明它们的命运通过量子干涉交织在一起。