Quantum interference of identical photons from remote GaAs quantum dots

Photonic quantum technology provides a viable route to quantum communication1,2, quantum simulation3 and quantum information processing4. Recent progress has seen the realization of boson sampling using 20 single photons3 and quantum key distribution over hundreds of kilometres2. 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 photons5,6,7,8,9. For applications, a roadblock is the poor quantum coherence on interfering single photons created by independent quantum dots10,11. 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.