Trapped ion

If you remove an electron from an atom, you get an electrically charged ion. An ion can be held floating in one spot in a vacuum by an electric field. Each ion held in a line like this is used as a qubit, and lasers are fired at them to change their states or entangle them with each other.

Atoms of the same kind are all identical, so the qubits are uniform in quality, their states last a long time, and operations are accurate. Another strength is that any ion in a line can be linked directly to any other. The downsides are that each operation takes much longer than in the superconducting approach, and it is hard to greatly increase the number of ions.

Picture beads hanging side by side in midair, with no string through them, and someone tapping them one at a time with a laser pointer to make them move.

Companies such as IonQ and Quantinuum use this approach. Which will reach useful calculations first, the slow but accurate approach or the fast but error-prone one, is one of the things to watch in the quantum race.