Two-Photon Interference from a Quantum Emitter in Hexagonal Boron Nitride

Indistinguishable single photons are a key requirement for most applications in optical quantum information. However, this feature has remained elusive among two-dimensional materials, primarily due to insufficient coherence of emitters. Here the authors controllably generate a spectrally narrow and stable single-photon source in an h-BN crystal by electron-beam irradiation, and demonstrate Hong-Ou-Mandel interference of the emitted photons, which is a signature of indistinguishability. These results enable practical applications in integrated quantum photonics based on two-dimensional materials.