One way to make a qubit out of superconductors is to fabricate a small island of superconducting material and count the extra electric charge sitting on it. There will be a baseline amount of charge on the island that minimizes energy, and adding any extra charge will raise the energy. The low-energy state and the higher-energy state can form a qubit, and the two states can be manipulated with microwaves (shown here as a white pulse). In superconductors, electrons team up into composite particles called Cooper pairs (depicted here as a cloud with two orbs), so the difference between the low-energy state and the higher-energy state is really two extra charges. (Credit: Olena Shmahalo)
Credit: Olena Shmahalo/The Quantum Atlas (CC BY-NC-SA 4.0)