The frictionless directional propagation of particles at the boundary of topological materials is a striking transport phenomenon. These chiral edge modes lie at the heart of the integer and fractional quantum Hall effects, and their robustness against noise and disorder reflects the quantization of Hall conductivity in these systems. Despite their importance, the controllable injection of edge modes, and direct imaging of their propagation, structure and dynamics, remains challenging. Here we demonstrate the distillation of chiral edge modes in a rapidly rotating bosonic superfluid confined by an optical boundary. By tuning the wall sharpness, we reveal the smooth crossover between soft wall behaviour in which the propagation speed is proportional to wall steepness and the hard wall regime that exhibits chiral free particles. From the skipping motion of atoms along the boundary we infer the energy gap between the ground and first excited edge bands, and reveal its evolution from the bulk Landau level splitting for a soft boundary to the hard wall limit. Finally, we demonstrate the robustness of edge propagation against disorder by projecting an optical obstacle that is static in the rotating frame.

粒子在拓扑材料边界处的无摩擦定向传播是一种引人注目的输运现象。这些手性边缘模式是整数和分数量子霍尔效应的核心，它们对噪声和无序的鲁棒性反映了这些系统中霍尔电导率的量化。尽管边缘模式很重要，但边缘模式的可控注入及其传播、结构和动力学的直接成像仍然具有挑战性。在这里，我们演示了受光学边界限制的快速旋转玻色超流体中手性边缘模式的蒸馏。通过调整壁的锐度，我们揭示了软壁行为（其中传播速度与壁陡度成正比）和表现出手性自由粒子的硬壁状态之间的平滑交叉。从原子沿边界的跳跃运动，我们推断出基带和第一激发边缘带之间的能隙，并揭示其从软边界的体朗道能级分裂到硬壁极限的演变。最后，我们通过投射旋转框架中静态的光学障碍物来证明边缘传播对抗无序的鲁棒性。