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Q: Fachverband Quantenoptik und Photonik

Q 7: Ultracold Matter II – Bosons (joint session Q/A)

Q 7.8: Talk

Monday, March 2, 2026, 18:45–19:00, P 2

Single Realization Spatially Resolved Velocity Reconstruction for a 2D BEC — •Jelte Duchene, Elinor Kath, Hanyi Jang, Helmut Strobel, and Markus Oberthaler — Kirchhoff-Institut für Physik, Universität Heidelberg

We present a method to extract both the velocity field and density of a 2D Bose-Einstein condensate (BEC) from single realizations. The method is based on Bragg spectroscopy extended to two dimensions, where two pairs counter propagating laser pulses with frequencies ω and ω + δ are incident on the atomic cloud and resonant with atoms according to their initial velocity. By imaging the scattered atoms after a short time of flight and modelling the Bragg beams as coupled two-level systems, we can reconstruct the spatially resolved velocity along the beam direction. A second pair of Bragg beams along a different axis allows us to extract the full 2D velocity field. Short Bragg pulses with a broad bandwidth address a broad band of velocities to enable the reconstruction of the full velocity field from a single realization of the BEC. We characterize the method by measuring the velocity profile of a single vortex and collective excitation of the system. This technique opens a path toward single-shot studies of 2D superfluid dynamics like the propagation of excitations, quantum turbulence, and vortex dynamics.

Keywords: BEC; Single Realization; Velocity Field; Bragg Spectroscopy; Quantum Turbulence