  Realization of quantum optical circuits is at the heart of quantum photonic
information processing. A long-standing obstacle however has been the absence
of a platform of single photon sources (SPSs) that simultaneously satisfies the
following required characteristics: spatially ordered SPS arrays that produce,
on-demand, highly pure, and indistinguishable single photons with sufficiently
uniform emission characteristics across the array, needed for controlled
interference between photons from distinct sources to enable functional quantum
optical networks. Here we report on such a platform of SPSs based upon a novel
class of epitaxial quantum dots. Under resonant excitation, the SPSs (without
Purcell enhancement) show single photon purity >99% (g(2)(0) ~ 0.015), high
two-photon Hong-Ou-Mandel interference visibilities of 0.82 $\pm$ 0.03 (at
11.5K), and spectral nonuniformity <3nm - within established locally tunable
technology. Our platform of SPSs paves the path to creating on-chip scalable
quantum photonic systems.
