Superconducting qubit
Qubits built as electrical circuits of superconducting metal — the technology IBM and Google backed, and the most built-out today.
The circuit contains a Josephson junction, a thin insulating barrier that gives the circuit unevenly spaced energy levels. That is decisive: with evenly spaced levels you cannot address just the lowest two, and you have no qubit. Control is by microwave pulses, the same frequency range as mobile telephony.
The advantage is that the circuits are made by lithography, much like ordinary chips, giving a clear path to more qubits. The price is that everything must sit at millikelvin in a dilution refrigerator, and that coherence times are short compared with trapped ions.