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978-3-8439-0643-2, Reihe Physik

Jakob Meineke
Fluctuations and Correlations in Ultracold Fermi Gases

170 Seiten, Dissertation Eidgenössische Technische Hochschule (ETH) Zürich (2012), Softcover, A5

Zusammenfassung / Abstract

In this thesis we present the first in-situ measurement of density- and spin-fluctuations in trapped ultracold Fermi gases with a spatial resolution on the intrinsic scale set by the Fermi wavelength. The measurement of the fluctuations gives direct experimental access to the correlation functions underlying the many-body properties of strongly interacting systems.

Using high-resolution imaging, we have observed the suppression of the density fluctuations below atomic shot-noise in quantum-degenerate, weakly interacting Fermi gases. This suppression is as a consequence of the quantum statistics obeyed by indistinguishable fermions and constitutes a measurement of antibunching in real space. We have also demonstrated a new method for measuring the temperature of trapped ultracold gases based on the fluctuation-dissipation theorem.

The measurement of the spin-fluctuations employs a shot-noise limited interferometer, which maps the spin-polarization of the atoms to a single mode of the light field. With this method we have studied the spin-fluctuations in weakly and strongly interacting

two-component Fermi gases and extract the spin-susceptibility. We interpret our measurement of the spin-fluctuations as a macroscopic entanglement witness, opening the way towards experimental investigations of entanglement in many-body systems.

In a complimentary approach, we have achieved the first conduction measurement with cold fermions by engineering macroscopic atom reservoirs connected by a narrow channel. Using high-resolution imaging and manipulation of the atoms, we have demonstrated the

emergence of a contact resistance, where the reservoirs and the channel connect. These measurements open the way towards the quantum simulation of mesoscopic devices.