  Nonclassical quantum effects gradually reach domains of physics of large
systems previously considered as purely classical. We derive a hierarchy of
operational criteria suitable for a reliable detection of nonclassicality of
light from an arbitrarily large ensemble of independent single-photon emitters.
We show, that such large ensemble can always emit nonclassical light without
any phase reference and under realistic experimental conditions including
incoherent background noise. The nonclassical light from the large ensemble of
the emitters can be witnessed much better than light coming from a single or a
few emitters.
