You can do it with electron spin or photon polarization or by any number of properties, but it's the state of a fundamental particle.
It's an entirely new type of computing apparatus, using the fundamental state of particles. No electron circuits, those won't work.
And it's expensive because of the above. These things are massive, have to be kept at cyrogenic temperature, and isolation gets harder the more particles you have.
You can implement them like that. Anything that has a quantum state that doesn’t decohere too fast will work. The hard part thus far has been that almost everything does decohere too fast.
It's an entirely new type of computing apparatus, using the fundamental state of particles. No electron circuits, those won't work.
And it's expensive because of the above. These things are massive, have to be kept at cyrogenic temperature, and isolation gets harder the more particles you have.