Free fermion antibunching in a degenerate atomic Fermi gas released from an optical lattice

Noise in a quantum system is fundamentally governed by the statistics and the many-body state of the underlying particles. The correlated noise observed for bosonic particles (for example, photons or bosonic neutral atoms) 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 and neutrons. Here we report the direct observation of antibunching of neutral fermionic atoms. By analysing 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 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.

[1]  Direct experimental evidence of free-fermion antibunching. , 2005, Physical review letters.

[2]  M. Lukin,et al.  Probing many-body states of ultracold atoms via noise correlations (4 pages) , 2003, cond-mat/0306226.

[3]  W. Phillips,et al.  Mott-insulator transition in a two-dimensional atomic Bose gas. , 2007, Physical review letters.

[4]  Michael Köhl,et al.  Correlations and counting statistics of an atom laser. , 2005, Physical review letters.

[5]  E. Demler,et al.  Interference between independent fluctuating condensates. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[6]  A. Aspect,et al.  Observations of density fluctuations in an elongated Bose gas: ideal gas and quasicondensate regimes. , 2005, Physical review letters.

[7]  Yamamoto,et al.  Hanbury brown and twiss-type experiment with electrons , 1999, Science.

[8]  R. H. Brown,et al.  Correlation between Photons in two Coherent Beams of Light , 1956, Nature.

[9]  Naoto Nagaosa,et al.  Doping a Mott insulator: Physics of high-temperature superconductivity , 2004, cond-mat/0410445.

[10]  Holland,et al.  The fermionic hanbury brown and twiss experiment , 1999, Science.

[11]  Spatial quantum noise interferometry in expanding ultracold atom clouds , 2005, Nature.

[12]  A. Georges,et al.  Interaction-induced adiabatic cooling and antiferromagnetism of cold fermions in optical lattices. , 2005, Physical review letters.

[13]  Y. Blanter,et al.  Shot noise in mesoscopic conductors , 1999, cond-mat/9910158.

[14]  Andreas Renz,et al.  Observation of Hanbury Brown–Twiss anticorrelations for free electrons , 2002, Nature.

[15]  Hanbury Brown Twiss Effect for Ultracold Quantum Gases , 2005, Science.

[16]  M. Lewenstein,et al.  Disordered ultracold atomic gases in optical lattices: A case study of Fermi-Bose mixtures , 2005, cond-mat/0508042.

[17]  Michael Köhl,et al.  Fermionic atoms in a three dimensional optical lattice: observing Fermi surfaces, dynamics, and interactions. , 2005, Physical review letters.

[18]  G. Baym.  THE PHYSICS OF HANBURY BROWN-TWISS INTENSITY INTERFEROMETRY: FROM STARS TO NUCLEAR COLLISIONS ∗ , 1997, nucl-th/9804026.

[19]  M. Lukin,et al.  Engineering superfluidity in Bose-Fermi mixtures of ultracold atoms , 2004, cond-mat/0410494.

[20]  Yasuda,et al.  Observation of Two-Atom Correlation of an Ultracold Neon Atomic Beam. , 1996, Physical review letters.

[21]  Probing pair-correlated fermionic atoms through correlations in atom shot noise. , 2005, Physical review letters.

[22]  E. Purcell,et al.  The Question of Correlation between Photons in Coherent Light Rays , 1956, Nature.

[23]  W. Phillips,et al.  The Mott insulator transition in two dimensions , 2006, cond-mat/0606216.

[24]  I Bloch,et al.  Exploring phase coherence in a 2D lattice of Bose-Einstein condensates. , 2001, Physical review letters.

[25]  J. Cirac,et al.  High-temperature superfluidity of fermionic atoms in optical lattices. , 2002, Physical review letters.

[26]  C.W.J. Beenakker,et al.  Quantum shot noise , 2003 .

[27]  L. Mandel,et al.  Optical Coherence and Quantum Optics , 1995 .

[28]  Quantum coherence of Hard-Core-Bosons and Fermions : Extended, Glassy and Mott Phases , 2006, cond-mat/0601307.