Fig. 3: Tunable and robust trap release of a BEC.

Release velocity of a transported BEC as a function of the initial hold time t_hold,i for the two transport ramps A (blue) and B (red) described in the caption of Fig. 2. Both transports allow for tunable release velocities between −1.5 mm s⁻¹ and +0.5 mm s⁻¹ with a minimal uncertainty of 0.117 mm s⁻¹ for t_hold,i = 2.8 ms (trap B) representing experimental noise. The release velocities are subject to a trap-dependent systematic shift (yellow and purple dashed lines) given by Δv_A = −0.98 ± 0.15 mm s⁻¹ and Δv_B = +0.062 ± 0.045 mm s⁻¹ caused by the finite switch-off time of the trap. The data (blue circles and red diamonds) is consistent with an ab-initio theoretical model (blue and red lines) based on a chip simulation and mean-field BEC dynamics (see Methods). The error bars and shaded areas show the 1σ-confidence bounds of the fits and the model, respectively.