Superconducting qubit
초전도 큐비트
A qubit built from a circuit cooled so cold that its electrical resistance disappears. IBM and Google, among others, use this approach.
Overview
Some metals lose all electrical resistance at very low temperatures. This is called superconductivity. A tiny circuit made from such a metal can be in a mix of two states, so it can serve as a qubit. It can borrow chip-making techniques from the semiconductor industry, which helps when you want to increase the number of qubits.
Its strength is that operations are very fast. In return, the qubit state is quickly disturbed, and a large refrigerator that cools the chip close to absolute zero is a must. As qubits increase, the wiring going into the refrigerator increases too, and cutting that down is a big challenge.
An everyday example
On well-polished ice, a sled you push once keeps sliding without stopping. In a superconducting circuit, electricity flows without obstruction in the same way, so delicate quantum states can be handled.
Why it matters
This approach is why news of "a quantum computer being installed" comes with a picture of a big refrigerator. It is also the approach used as the yardstick when you compare the pros and cons of other kinds of quantum computers.