Neutral-Atom Systems

Neutral-atom machines hold single uncharged atoms in tightly focused laser beams, called optical tweezers. They entangle nearby atoms through the Rydberg blockade. This is a strong effect that only works over a short distance. So the layout of the atoms is itself the map of which qubits can link. Atoms can even be moved during a job. That swaps extra routing gates for time spent moving.

What is a neutral-atom machine?

A neutral atom is an ordinary atom with no electric charge. These machines often use rubidium, caesium, strontium or ytterbium. With no charge, the electric traps that hold ions get no grip on it. So the tool is an optical tweezer instead. This is a laser beam focused to a spot so tight that a single atom is pulled to the focus and held there. It is a pair of tweezers made of light.

One laser can be split into many beams by a part that shapes light under computer control. It becomes hundreds or thousands of tweezers at once, each holding one atom. Software sets where each atom sits: grids, triangles, rings, almost any flat pattern. (3D layouts have been shown too.) Picture a muffin tray where you can move the cups around with a computer.

Arrays of several hundred to over a thousand trapped atoms exist today. Note that this is a count of trapped atoms. That is not the same claim as that many qubits all doing high-quality computing at once.

As with ions, the qubit lives in two stable inner states of the atom. Every atom of the same isotope (the same exact kind of atom) is identical. There is no factory variation.