A tiny cloud of 300,000 ytterbium atoms, cooled to near absolute zero, was shuttled along a light track 34 centimeters long, like transporting a fragile cargo over a bumpy road without shaking it apart. Normally, such moves heat the atoms due to vibrations and trap irregularities, but here two laser beams combined into an 'optical lattice'—a row of light cells that move along with the atoms, like an escalator's steps.
Physicists used Bessel beams, which do not spread out along the way, so the cells remain sharp throughout the route. In 350 milliseconds, the cloud traveled 34 centimeters, and more than half of the atoms reached the destination without falling out of the trap. Then the atoms were allowed to cool further, and they spontaneously synchronized into a single quantum state — a Bose-Einstein condensate, where all particles behave as one wave.
Such a 'conveyor belt' could enable rapid assembly of large arrays of cold atoms for quantum simulators and computers. Instead of preparing each qubit individually, one could deliver them in batches, like parts on an assembly line.
The gas temperature at the start of the journey was 340 nanokelvins, a billion times colder than room temperature, and the atoms moved at only a few centimeters per second.
A similar principle of light traps is described in Sergei Lukyanenko's novel 'Firefly', where characters move objects using laser beams.