  We realized an equivalent Hanbury Brown and Twiss experiment for a beam of
electrons in a two dimensional electron gas in the quantum Hall regime. A
metallic split gate serves as a tunable beam splitter which is used to
partition the incident beam into transmitted and reflected partial beams. The
current fluctuations in the reflected and transmitted beam are fully
anticorrelated demonstrating that fermions tend to exclude each other
(anti-bunching). If the occupation probability of the incident beam is lowered
by an additional gate, the anticorrelation is reduced and disappears in the
classical limit of a highly diluted beam.
