Trapped-ion qubit

A qubit stored in the internal energy levels of a single charged atom, held in a vacuum by electric fields.

• Ions levitate micrometres above a chip-like trap, and lasers or microwaves set and read their states.
• Every ion of an element is identical and well isolated, giving the best gate accuracy so far: above 99.9% for two-qubit gates.
• Ions interact through shared vibrations and can be shuttled around the trap, so any qubit can be paired with any other.
• Gates take tens to hundreds of microseconds, roughly 1,000× slower than superconducting ones, and controlling very many ions is hard.