The photon statistics emitted by a large variety of light‐matter systems under weak coherent driving can be understood, to lowest order in the driving, in the framework of an admixture of (or interference between) a squeezed state and a coherent state, with the resulting state accounting for all bunching and antibunching features. One can further identify two mechanisms that produce resonances for the photon correlations: i) conventional photon blockade describes cases that involve a particular quantum level or set of levels in the excitation/emission processes with interferences occurring to all orders in the photon numbers, while ii) unconventional photon blockade describes cases where the driving laser is far from resonance with any level and the interference occurs for a particular number of photons only, yielding stronger correlations but only for a definite number of photons. Such an understanding and classification allows for a comprehensive and transparent description of the photon statistics from a wide range of disparate systems, where optimum conditions for various types of photon correlations can be found and realized.

中文翻译：

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常规和非常规光子统计

在压缩状态和相干状态的混合（或相互干扰）的框架下，弱相干驱动下各种光系统发射的光子统计可以理解为驱动中的最低阶。结果状态说明了所有聚集和反聚集功能。可以进一步确定产生光子相关性共振的两种机制：i）传统的光子阻断描述了在激发/发射过程中涉及特定量子能级或一组能级的情况，而光子数中所有阶次都发生了干扰，而ii ）非常规光子封锁描述了以下情况：驱动激光器远离任何水平的共振，并且仅对特定数量的光子产生干扰，产生更强的相关性，但仅适用于一定数量的光子。这样的理解和分类允许从各种不同的系统中对光子统计数据进行全面，透明的描述，在其中可以找到并实现各种类型的光子相关性的最佳条件。