= Con of superconducting qubits
* requires intense refrigeration to 15mK in <dilution refrigerator>. Note that this is much lower than the actual <superconducting temperature> of the metal, we have to go even lower to reduce noise enough, see e.g. https://youtu.be/uPw9nkJAwDY?t=471 from <video Building a quantum computer with superconducting qubits by Daniel Sank (2019)>
* less connectivity, normally limited to 4 nearest neighbours, or maybe 6 for 3D approaches, e.g. compared to <trapped ion quantum computers>, where each trapped ion can be entangled with every other on the same chip