  Multi-photon entangled states such as `N00N states' have attracted a lot of
attention because of their possible application in high-precision phase
measurements. So far, N00N states have been generated by spontaneous parametric
down-conversion sources and by mixing quantum and classical light on a beam
splitter. However, single-photon on demand sources promise to be more efficient
and scalable than down-conversion sources which are probabilistic in nature.
Here, we demonstrate super-resolving phase measurements based on two-photon
N00N states generated by a quantum dot single-photon source utilizing the
Hong-Ou-Mandel effect on a beam splitter. The quantum dot was excited through a
two-photon resonant excitation scheme. Using a $\pi$-pulse, this results in the
deterministic generation of indistinguishable single photons from both, the
biexciton and exciton radiative recombination processes. Launching either type
of the photons into both inputs of an interferometer, phase super-resolution,
i.e. an interference fringe spacing with doubled rate relative to the single
photon rate has been observed for both transitions. Interference visibilities
of $V_{N=2,\mathit{XX}}=0.54\pm0.01$ for the biexciton and
$V_{N=2,\mathit{X}}=0.46\pm0.02$ for the exciton transition have been obtained,
respectively.
