I once saw a cut out of a D-wave computer (not a "real" quantum computer but also cryogenic). The whole device is roughly the size of a old school mainframe - a

I once saw a cut out of a D-wave computer (not a "real" quantum computer but also cryogenic). The whole device is roughly the size of a old school mainframe - a few wardrobes. But it's mostly layers of insulation and cooling. The business bit inside fits in your hand. Or so I remember at least. Actual cooling (stuff that pumps liquid nitrogen and helium) was external to all this.