Barredo and team report their use of precision optical-engineering methods to sort atoms into arbitrary 3D patterns.

Barredo et al. extend their previously reported method for 2D atom sorting to three dimensions. Their approach to disorder and sorting is different from Kumar and colleagues' method, but just as effective. They use a holographic technique whereby a laser beam is reflected off a spatial light modulator and then focused to form traps known as optical tweezers. In this way, they generate arrays of traps in arbitrary configurations that can be loaded with up to 72 cold rubidium atoms. To remove disorder and build the desired atomic configuration, the authors use a separate, movable optical tweezer to pluck atoms from 'wrong' traps and either move them to correct sites or discard them. This allows them to build qubit arrays in standard grid patterns, in topologies such as a Möbius strip, and even in the shape of the Eiffel Tower.