Quantum Newton's cradles
Images of quantum Newton's cradles during their first cycle of oscillation. Atoms are confined to one dimension (1D) in 3000 parallel tubes, with an average of 110 atoms per tube. Each atom collides with half the other atoms twice each 13 ms cycle, sometimes bouncing off each other, sometimes passing through each other. The radius of each tube in the bundle is 40 nm. The tubes are 385 nm apart, and are not individually resolved. The bundle of tubes is viewed from the side, with the false colour in each image rescaled to show detail. The maximum extent of each 1D gas is about 30 microns while they oscillate. They are allowed to expand in their tubes to a length of 1 mm before these pictures are taken. The cartoon steel balls drawn at the top of the picture are for illustrative purposes, to make the analogy between the quantum and classical Newton's cradle clear (image and text courtesy: David Weiss).