Transmon
The most widely deployed superconducting qubit: a Josephson junction shunted by a large capacitor to blunt the stray charge noise that plagued earlier designs.
The transmon is the most widely deployed superconducting qubit design, the one Google, IBM, and Rigetti processors are built from. Invented at Yale in 2007, it's a Josephson junction shunted by a large capacitor, a tweak that makes the qubit far less sensitive to stray electric charge, the noise source that plagued earlier designs.
The trade was deliberate: a little less anharmonicity (the unevenness in energy levels that lets you address the qubit) in exchange for a lot more stability. Coherence times went from nanoseconds in the early 2000s to hundreds of microseconds today, largely on the back of that design choice and better materials.
When the millikelvin writes about 'superconducting chips,' transmons are almost always what's on them.