The image illustrates the collective optical properties of semiconductor perovskite nanocrystals under the excitation of upper blue laser ray. The cubic perovskite nanocrystals exhibit amplified spontaneous emission (ASE) tunable from near UV to near Infrared on the right side. Three sequential bright dots and decaying sinusoidal wave on the lower side represent single photon emission and quantum coherence in perovskite nanocrystals, respectively. Meanwhile, the discrete energy levels and photoluminescence spectrum on the left side correspond to the fine structure of perovskite nanocrystals.