Trapped ion
Qubits made from individual ions held suspended in electromagnetic fields and controlled with lasers — slower than superconductors, but considerably more precise.
The ions are held in a trap and laser-cooled until they are nearly still. Two energy levels of the ion form the qubit. A decisive advantage is that all ions of the same species are exactly identical — superconducting qubits are manufactured and therefore carry individual deviations that must be calibrated away.
Coherence times are outstanding, seconds rather than microseconds, and error rates are among the lowest measured. Any ion can also be coupled to any other through their shared motion, avoiding the nearest-neighbour constraint. The downside is speed: gates take microseconds against nanoseconds, and scaling to many ions in one trap is hard. IonQ and Quantinuum pursue this route.