  Resonant excitation of atoms and ions in macroscopic cavities has lead to
exceptional control over quanta of light. Translating these advantages into the
solid state with emitters in microcavities promises revolutionary quantum
technologies in information processing and metrology. Key is resonant optical
reading and writing from the emitter-cavity system. However, it has been widely
expected that the reflection of a resonant laser from a micro-fabricated
wavelength-sized cavity would dominate any quantum signal. Here we demonstrate
coherent photon scattering from a quantum dot in a micro-pillar. The cavity is
shown to enhance the fraction of light which is resonantly scattered towards
unity, generating anti-bunched indistinguishable photons a factor of 16 beyond
the time-bandwidth limit, even when the transition is near saturation. Finally,
deterministic excitation is used to create 2-photon N00N states with which we
make super-resolving phase measurements in a photonic circuit.
