An ordinary flash drive in your pocket gets warm even when it's just sitting there. Now imagine memory that, in the cold, uses almost nothing, like a thermos that never cools down. A superconductor carries current without loss at liquid-helium temperatures, but it couldn't store data. The new cell changes that.

Inside is a layered sandwich of niobium and magnetic films. A magnetic field shifts the superconductor's energy gap, and the tunneling current through the barrier changes. This yields two clear voltage levels — zero and one.

Such memory is needed right next to quantum processors: ordinary electronics introduce heat and noise. Here, the design is vertical, like a stack of pancakes, which can be printed by the millions on a single wafer. A quantum computer gets a fast, cold "notebook."