It’s not much to look at. Its case—the size of a pack of chewing gum--is connected to wires that transmit signals to a nearby panel of custom radiofrequency receivers. But most important, it’s nestled within a shiny gold cocoon called a dilution refrigerator and shielded from stray electrical signals. When the refrigerator is running, it is among the coldest places on Earth, so very close to absolute zero, less than 6 millikelvin (about −460 degrees F).
This is the right answer. It's a big cryogenic refrigerator called a Dilution Refrigerator. It's fancy stuff. Needs Helium-4, which is more common, and Helium-3, which mostly comes from nuclear production.
lots of fun techniques, a common one for getting down low enough where other methods become practical is stirling cryocoolers, and those are even on ebay for a few thousand (cascade refrigeration systems, and joule thompson coolers, and a few others are also used), way down past that theres stuff like weird magnetic coolers, and dilution coolers All very interesting, reading about exotic cooling methods is quite fun.