Non-classicality of output states of quantum channels with indefinite causal order is studied, where each channel maps any state to a fixed one. The causal indefiniteness means a coherent superposition of the order of which channel first interacts with a quantum system. Non-classicality of a single-mode photon system is investigated in terms of the non-classical depth and the Mandel Q-parameter. It is shown that the thermalizing channels with indefinite causal order can create non-classicality even when an input state is classical.

中文翻译：

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具有不确定因果顺序的量子通道所产生的非经典性

研究了具有不确定因果顺序的量子通道输出状态的非经典性，其中每个通道将任何状态映射到固定状态。因果不确定性是指通道首先与量子系统相互作用的顺序的相干叠加。根据非经典深度和Mandel Q参数研究了单模光子系统的非经典性。结果表明，具有不确定因果顺序的热通道即使在输入状态为经典状态时，也会产生非经典性。