Quantum interference of identical photons from remote GaAs quantum dots.

Photonic quantum technology provides a viable route to quantum communication 1,2 , quantum simulation 3 and quantum information processing 4 . Recent progress has seen the realization of boson sampling using 20 single photons 3 and quantum key distribution over hundreds of kilometres 2 . Scaling the complexity requires architectures containing multiple photon sources, photon counters and a large number of indistinguishable single photons. Semiconductor quantum dots are bright and fast sources of coherent single photons 5-9 . For applications, a roadblock is the poor quantum coherence on interfering single photons created by independent quantum dots 10,11 . Here we demonstrate two-photon interference with near-unity visibility (93.0 ± 0.8)% using photons from two completely separate GaAs quantum dots. The experiment retains all the emission into the zero phonon line-only the weak phonon sideband is rejected; temporal post-selection is not employed. By exploiting quantum interference, we demonstrate a photonic controlled-not circuit and an entanglement with fidelity of (85.0 ± 1.0)% between photons of different origins. The two-photon interference visibility is high enough that the entanglement fidelity is well above the classical threshold. The high mutual coherence of the photons stems from high-quality materials, diode structure and relatively large quantum dot size. Our results establish a platform-GaAs quantum dots-for creating coherent single photons in a scalable way.