  Superradiance is one of the outstanding problems in quantum optics since
Dicke introduced the concept of enhanced directional spontaneous emission by an
ensemble of identical two-level atoms. The effect is based on correlated
collective Dicke states which turn out to be highly entangled. Here we show
that enhanced directional emission of spontaneous radiation can be produced
also with statistically independent incoherent sources via the measurement of
higher order correlation functions of the emitted radiation. Our analysis is
applicable to a wide variety of quantum systems like trapped atoms, ions,
quantum dots or NV-centers, and is also valid for statistically independent
incoherent classical emitters. This is experimentally confirmed with up to
eight independent thermal light sources.
