My question is that I've seen superconducting quantum interference devices that use JJs that are a few inches big, so why do flux qubits have to be ludicrously small? Do they have to be small, or is that a question outside of physics altogether, more so for a question of mass production instead?
The reason behind this is that I'm looking to create a pulse tube based flux qubit machine with Pb as my material for the JJs. Since the prototype SQUIDs are rather big, I figured I could build them too, without expensive equipment. Considering a pulse tube refrigerator can be made with copper, PVC pipes, and reciprocating saws, I'm sure cooling wouldn't be an issue. The noise, however...is another question. I realize this is extremely ambitious, but I appreciate any help you can give me.