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Interferometric measurement of local spin fluctuations in a quantum gas

Nature Physics volume 8, pages 454–458 (2012)Cite this article

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Abstract

Ultracold gases provide a controlled environment that is ideal for studying many intriguing phenomena associated with quantum correlated systems1. Current efforts are directed towards the identification of magnetic properties2,3,4, as well as the creation and detection of exotic quantum phases5,6,7. In this context, a mapping of the spin polarization of the atoms to the state of a single-mode light beam has been proposed8. Here we introduce a quantum-limited interferometer that realizes such an atom–light interface9 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.

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Figure 1: Interferometer set-up.
Figure 2: Interferometer performance.
Figure 3: Spin fluctuations in ultracold Fermi gases.

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Acknowledgements

We acknowledge enlightening discussions with M. Christiandl, A. Imamoglu, K. Mølmer, E. Polzik, R. Renner, A. Sørensen, M. Ueda and V. Vuletic and funding from National Centres of Competence in Research (NCCR) MaNep, NCCR QSIT, European Research Council (ERC) SQMS and FP7 FET-open NameQuam. J-P.B. acknowledges the support of the European Union under a Marie Curie IEF fellowship.

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Authors and Affiliations

  1. Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland

    Jakob Meineke, Jean-Philippe Brantut, David Stadler, Torben Müller & Tilman Esslinger

  2. Institut für Laser-Physik, Universität Hamburg, 22761 Hamburg, Germany

    Henning Moritz

Authors
  1. Jakob Meineke
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  2. Jean-Philippe Brantut
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  3. David Stadler
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  4. Torben Müller
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  5. Henning Moritz
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  6. Tilman Esslinger
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Contributions

J.M. and J-P.B. analysed the data. J.M., J-P.B., D.S. and T.M. carried out the experimental work. All authors contributed to project planning and to writing the manuscript.

Corresponding author

Correspondence to Tilman Esslinger.

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The authors declare no competing financial interests.

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Meineke, J., Brantut, JP., Stadler, D. et al. Interferometric measurement of local spin fluctuations in a quantum gas. Nature Phys 8, 454–458 (2012). https://doi.org/10.1038/nphys2280

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