There are two things relevant to this design: 1. what you are looking at is basically a freezer; For certain effects you need a very very low temperature. 2.

There are two things relevant to this design: 1. what you are looking at is basically a freezer; For certain effects you need a very very low temperature. 2. Gold in general is a very good material as it is very stable and doesn't react with a lot of stuff (it is not very corrosive). It also conducts electricity very well. I would also argue, that what you see is normally the open version of it or it was opend to show the inside: https://www.information-age.com/ibm-commercial-quantum-computer-q-system-one-123477940/ https://www.information-age.com/ibm-commercial-quantum-compu... they are in tubes; Might even be vacuum. Also heat goes up, cold stays down; might also have influecned the design but actually you are probably better of asking a physics person :D