1. Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany

Correspondence to: I. Bloch¹ Correspondence and requests for materials should be addressed to I.B. (Email: bloch@uni-mainz.de).

Abstract

Noise in a quantum system is fundamentally governed by the statistics and the many-body state of the underlying particles^{1, 2, 3, 4}. The correlated noise^{5, 6, 7} observed for bosonic particles (for example, photons⁸ or bosonic neutral atoms^{9, 10, 11, 12, 13, 14}) can be explained within a classical field description with fluctuating phases; however, the anticorrelations ('antibunching') observed in the detection of fermionic particles have no classical analogue. Observations of such fermionic antibunching are scarce and have been confined to electrons^{15, 16, 17} and neutrons¹⁸. Here we report the direct observation of antibunching of neutral fermionic atoms. By analysing the atomic shot noise^{3, 10, 19} 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 characterize 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.

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