Extended Data Fig. 6: Determination of the edge mode velocity.

a, In situ images of atoms in the optical tweezer. The position of the tweezer is varied from top to bottom by steps of 0.48 μm in the x direction (perpendicular to the orientation of the edge), as emphasized by the vertical dashed line. The pictures are an average of five individual experimental realizations, performed without the edge potential in order to better see the displacement of the tweezer. The scale bar corresponds to 10a. b-c, Evolution of the cloud for the two chiralities. The first line shows the average of the absorption images after an increasing evolution time, displayed with the same colorscale. The second line shows the result of the Gaussian fit that is performed on the averaged images. On these fits, the center of the Gaussian is indicated as a black dot. The error bar, which stems from a bootstrap analysis, is smaller than the marker. d, The absolute distance Δr between the center-of-mass positions of the time-evolved clouds with the two different chiralities is plotted as a function of the time. The five different markers correspond to the five initial positions, and the corresponding solid lines are linear fits. e, The slope of the fit is divided by a factor of two to obtain the average velocity of the edge mode. The measured velocity is plotted as a function of the initial position, and the final value that is selected is the maximum value of these points. The markers are the same as d. For the leftmost tweezer position the error bar is very large: the atoms are released on top of the potential step and no reliable velocity can be extracted.