If you’ve seen an image of a quantum computer, chances are it wasn’t working. The most photogenic part is inside, visible only when the machine is switched off. The industry calls it a chandelier: an ornate tower of braided wires and copper plated with gold. It’s designed this way to protect fragile circuits at the bottom from any heat or outside disturbance so they can perform calculations. To operate, the whole apparatus must be placed inside a massive stainless-steel vacuum chamber to kick of...