  Noise in a quantum system is fundamentally governed by the statistics and the
many-body state of the underlying particles. Whereas for bosonic particles the
correlated noise observed for e.g. photons or bosonic neutral atoms can still
be explained within a classical field description with fluctuating phases, the
anticorrelations in the detection of fermionic particles have no classical
analogue. The observation of such fermionic antibunching is so far scarce and
has been confined to electrons and neutrons. Here we report on the first direct
observation of antibunching of neutral fermionic atoms. Through an analysis of
the atomic shot noise in a set of standard absorption images, of a gas of
fermionic 40K atoms released from an optical lattice, we find reduced
correlations for distances related to the original spacing of the trapped
atoms. The detection of such quantum statistical correlations has allowed us to
characterise the ordering and temperature of the Fermi gas in the lattice.
Moreover, our findings are an important step towards revealing fundamental
fermionic many-body quantum phases in periodic potentials, which are at the
focus of current research.
