Jakob Meineke, Jean-Philippe Brantut, David Stadler, Torben Müller, Henning Moritz, Tilman Esslinger
The subtle interplay between quantum statistics and interactions is at the
origin of many intriguing quantum phenomena connected to superfluidity and
quantum magnetism. The controlled setting of ultracold quantum gases is well
suited to study such quantum correlated systems. Current efforts are directed
towards the identification of their magnetic properties, as well as the
creation and detection of exotic quantum phases. In this context, it has been
proposed to map the spin-polarization of the atoms to the state of a
single-mode light beam. Here we introduce a quantum-limited interferometer
realizing such an atom-light interface with high spatial resolution. We measure
the probability distribution of the local spin-polarization in a trapped Fermi
gas showing a reduction of spin-fluctuations by up to 4.6(3) dB below
shot-noise in weakly interacting Fermi gases and by 9.4(8) dB for strong
interactions. We deduce the magnetic susceptibility as a function of
temperature and discuss our measurements in terms of an entanglement witness.
View original:
http://arxiv.org/abs/1202.5250
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