Quantum backflow is a counterintuitive phenomenon in which a forward-propagating quantum particle propagates locally backwards. The actual counter-propagation property associated with this delicate interference phenomenon has not been observed to date in any field of physics, to the best of our knowledge. Here, we report the observation of an analog optical effect, namely, transverse optical backflow where a beam of light propagating to a specific transverse direction is measured locally to propagate in the opposite direction. This observation is relevant to any physical system supporting coherent waves.

中文翻译：

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观察光学倒流

量子回流是一种违反直觉的现象，其中向前传播的量子粒子局部向后传播。据我们所知，迄今尚未在任何物理学领域观察到与这种微妙的干扰现象相关的实际反向传播特性。在这里，我们报告了对模拟光学效应的观察，即横向光学逆流，其中局部测量了沿特定横向传播的光束在相反方向上传播。该观察结果与支持相干波的任何物理系统有关。