What D-Wave has done is begun with the standard approaches to building metal-based processors and modified them in such a way that these processors use quantum mechanics in order to accelerate computation.
The chip in the middle is 5 square mm in size.
Superconductors are the only type of material that we know of where big lithographically defined devices (like really big. Like centimeter on a side big.) can be built that behave just like they were atomic-sized. The reason for this behavior is highly technical - is has to do with the types of particles in the material. In a superconductor all of the “particles” that carry charge around can exist in the exact same state, so when you look at a whole lot of these particles (many trillions) it can be just like looking at only one (which is “very quantum mechanical”).
This property allows us to build circuits out of superconductors that, if we are really smart and really careful, can be made to act like “circuits of atoms”. We can use the fact that really big things (which we can easily build today using conventional fabrication techniques) can be made to behave like really small things to try to build real quantum computing architectures.
adiabatic quantum computer
superconducting quantum computer