We investigate Dicke subradiance of $N\ge 2$ distant quantum sources in free space, i.e., the spatial emission patterns of spontaneously radiating noninteracting multilevel atoms or multiphoton sources, prepared in totally antisymmetric states. We find that the radiated intensity is marked by a full suppression of spontaneous emission in particular directions. In resemblance to the analogous, yet inverted, superradiant emission profiles of $N$ distant two-level atoms prepared in symmetric Dicke states, we call the corresponding emission patterns directional Dicke subradiance. We further derive that higher-order intensity correlations of the light emitted by statistically independent thermal light sources display the same directional Dicke subradiant behavior and show that it stems from the same interference phenomenon as in the case of quantum sources. We finally present measurements of directional Dicke subradiance for $N=2,\dots ,5$ distant thermal light sources corroborating the theoretical findings.

中文翻译：

---

非经典和经典光源的定向Dicke次辐射度

我们调查了Dicke的 $ñ\ge \mathrm{2个}$自由空间中的遥远量子源，即以完全反对称状态准备的自发辐射非相互作用多能级原子或多光子源的空间发射模式。我们发现，辐射强度的特征是在特定方向上完全抑制了自发辐射。与类似但反向的超辐射发射曲线相似$ñ$在对称迪克状态下制备的遥远两能级原子，我们将相应的发射模式称为定向迪克亚辐射。我们进一步得出，统计上独立的热光源发出的光的高阶强度相关性显示出相同的定向迪克次辐射行为，并表明它源自与量子源相同的干涉现象。我们最终提出了定向Dicke次辐射的测量$ñ=\mathrm{2个}，\dots ，5$ 遥远的热光源证实了理论发现。