Hong–Ou–Mandel interference in colloidal CsPbBr 3 perovskite nanocrystals

In the search for novel, robust quantum emitters, inorganic lead halide perovskite nanocrystals have emerged as potential colloidal sources of coherent single photons. While colloidal perovskite nanocrystals offer a great source of synthetically scalable, tunable photon sources, observation of two-photon quantum interference from the emission of any colloidal nanoparticle has not been previously reported. In this work we prepare large CsPbBr 3 nanocrystals and observe direct evidence of interference between indistinguishable single photons sequentially emitted from a single nanocrystal. We measure Hong–Ou–Mandel interference from photons in CsPbBr 3 nanocrystals, showing corrected visibilities of up to 0.56 ± 0.12 in the absence of any radiative enhancement or photonic architecture. These results demonstrate the unique potential of perovskite nanocrystals to serve as scalable, colloidal sources of indistinguishable single photons.