Mainz 2026 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 42: Poster – Ultracold Matter (joint session Q/A)

Q 42.31: Poster

Mittwoch, 4. März 2026, 17:00–19:00, Philo 2. OG

Velocity field extraction from ultracold gases using bragg scattering — •hanyi jang, elinor kath, jelte duchene, helmut strobel, and markus k. oberthaler — Kirchhoff-Institut für Physik, Heidelberg, Germany

An ultracold quantum gases velocity field offers information about phase, topological defects and transport mechanisms. We have developed a method of estimating the velocity field by Bragg scattering from a moving optical lattice, which enables velocity selective two-photon transition between momentum states. To reconstruct the spatial velocity field of a 2-dimensional Bose-Einstein condensate (BEC), we explored two techniques. A short Bragg pulse generates a broad band response that simultaneously probes a spectrum of velocities, which is advantages for non-reproducible systems. In contrast, a long Bragg pulse produces narrow spectral response that probes single velocity with a higher precision. To assess the performance of the two methods, we benchmark them experimentally on a well-controlled scenario of stationary single vortex in the BEC. We extract the radial velocity profile centered on the vortex core and compare it to the analytic theory prediction and Gross-Pitaevskii simulation.

Keywords: Bragg Scattering; Vortex; Bose-Einstein condensate; Gross-Pitaevskii simulation; Velocity field