Berlin 2014 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 32: Poster: Quantum gases, ultracold atoms and molecules

Q 32.67: Poster

Mittwoch, 19. März 2014, 16:30–18:30, Spree-Palais

Direct imaging of the momentum distribution of a two-dimensional quantum gas — •Puneet Murthy1, Martin Ries1, Mathias Neidig1, Sebastian Pres1, Dhruv Kedar1, Andre Wenz1, Gerhard Zürn1, Thomas Lompe2, and Selim Jochim11Physikalisches Institut, Heidelberg, Germany — 2Massachusetts Institute of Technology, Cambridge, USA

We report a new technique to directly probe the in-situ radial momentum distribution of a 2D gas of ultracold atoms. After turning off the initial 2D confinement, which instantaneously switches off interactions, we let the gas evolve radially in a harmonic trap whereby the initial momentum distribution is mapped to the spatial distribution after a quarter of the trap period (T/4). However, the fast expansion of the 2D gas along the axial direction prohibits imaging at T/4 with sufficient resolution. We overcome this limitation by pulsing an optical harmonic potential, thereby significantly reducing the axial expansion, while keeping the gas dilute enough to prevent collisions.

Additionally, we propose a method to "zoom in" to the momentum distribution in a controlled manner. For this, we exploit the fact that atoms with opposite magnetic moments interact contrarily with magnetic field gradients. Thus, by sequentially transferring atoms between high-field and low-field seeking states, the initial momentum distribution can be mapped to a magnified spatial distribution. These two complementary techniques can be applied to a wide range of experiments involving 2D gases and will be particularly important to probing the many-body phases of quantum gases in 2D lattice potentials.

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