  Photonic quantum technologies are on the verge of finding applications in
everyday life with quantum cryptography and the quantum internet on the
horizon. Extensive research has been carried out to determine suitable quantum
emitters and single epitaxial quantum dots are emerging as near-optimal sources
of bright, on-demand, highly indistinguishable single photons and entangled
photon pairs. In order to build up quantum networks, it is now essential to
interface remote quantum emitters. However, this is still an outstanding
challenge, as the quantum states of dissimilar 'artificial atoms' have to be
prepared on-demand with high fidelity, and the generated photons have to be
made indistinguishable in all possible degrees of freedom. Here, we overcome
this major obstacle and show an unprecedented two-photon interference
(visibility of 51+/-5%) from remote strain-tunable GaAs quantum dots, emitting
on-demand photon-pairs. We achieve this result by exploiting for the first time
the full potential of the novel phonon-assisted two-photon excitation scheme,
which allows for the generation of highly indistinguishable (visibility of
71+/-9%) entangled photon-pairs (fidelity of 90+/-2%), it enables push-to
button biexciton state preparation (fidelity of 80+/-2%) and it outperforms
conventional resonant two-photon excitation schemes in terms of robustness
against environmental decoherence. Our results mark an important milestone for
the practical realization of quantum repeaters and complex multi-photon
entanglement experiments involving dissimilar artificial atoms.
