  We report on the observation of single-photon superradiance from an exciton
in a semiconductor quantum dot. The confinement by the quantum dot is strong
enough for it to mimic a two-level atom, yet sufficiently weak to ensure
superradiance. The electrostatic interaction between the electron and the hole
comprising the exciton gives rise to an anharmonic spectrum, which we exploit
to prepare the superradiant quantum state deterministically with a laser pulse.
We observe a five-fold enhancement of the oscillator strength compared to
conventional quantum dots. The enhancement is limited by the base temperature
of our cryostat and may lead to oscillator strengths above 1000 from a single
quantum emitter at optical frequencies.
