Room-temperature single-photon source with near-millisecond built-in memory.

Non-classical photon sources are a crucial resource for distributed quantum networks. Photons generated from matter systems with memory capability are particularly promising, as they can be integrated into a network where each source is used on-demand. Among all kinds of solid state and atomic quantum memories, room-temperature atomic vapours are especially attractive due to their robustness and potential scalability. To-date room-temperature photon sources have been limited either in their memory time or the purity of the photonic state. Here we demonstrate a single-photon source based on room-temperature memory. Following heralded loading of the memory, a single photon is retrieved from it after a variable storage time. The single-photon character of the retrieved field is validated by the strong suppression of the two-photon component with antibunching as low as $${g}_{{\rm{RR| W = 1}}}^{(2)}=0.20\pm 0.07$$ . Non-classical correlations between the heralding and the retrieved photons are maintained for up to $${\tau }_{{\rm{NC}}}^{{\mathcal{R}}}=(0.68\pm 0.08)\ {\rm{ms}}$$ , more than two orders of magnitude longer than previously demonstrated with other room-temperature systems. Correlations sufficient for violating Bell inequalities exist for up to τBI = (0.15 ± 0.03) ms. Room-temperature single photon sources with memory capabilities are promising for quantum information processing, but are currently limited in their memory time or photon purity. Here, the authors report single photon emission with good antibunching from an atomic vapour cell source with 0.68 ms memory time.