Marc CHENEAU(1), Jacob SHERSON(1,*), Christof WEITENBERG(1), Manel ENDRES(1), Immanuel BLOCH(1,2) and Stefan KUHR(1)
(1) Max-Planck-Institut fu ̈r Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany.
(2) Ludwig-Maximilians-Universita ̈t, Schellingstraße 4/II, D-80799 Mu ̈nchen, Germany.
(*) Present address: Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
We report on the recent fluorescence imaging of bosonic Mott insulators in an optical lattice with single- atom and single-site resolution . From the images we obtain, we are able to fully reconstruct the atom distribution on the lattice and to identify individual thermal excitations with high fidelity. The compar- ison of the radially averaged density and variance distributions with a simple model provides a precise in-situ temperature measurement from single images. We observe Mott-insulating plateaus with near zero entropy and clearly resolve the high-entropy rings separating them, although their width is of the order of a single lattice site. Furthermore, we show how a Mott insulator “melts” for increasing temperature due to the proliferation of local defects. These experiments open a new avenue for the manipulation and analysis of strongly-correlated quantum gases on a lattice, as well as for quantum information processing with ultracold atoms. It should allow, for example, the implementation of new cooling schemes relying on the local addressing of high-entropy regions of a many-body state. The observation and characterization of the propagation of a local excitation may also be soon within reach.
 J. Sherson, C. Weitenberg, M. Endres, M. Cheneau, I. Bloch and S. Kuhr, Nature 467, 68 (2010)
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