What’s cooler than being cool?

The coldest place in the universe is not in the void of deep space, which sits at about 2.7 Kelvin—the leftover heat from the Big Bang. It is inside a machine the size of an elevator car, built in Helsinki, Finland, that cools a space the size of a baseball card down to 0.02 degrees Kelvin. These machines are called dilution refrigerators, and they are at the center of a quiet but urgent race: the race for the future of cold.

What temperature actually is

Temperature is a measure of how fast molecules are moving. The faster they move, the hotter something is; the slower they move, the colder it is. Absolute zero—zero Kelvin—is the theoretical point where molecular motion stops entirely, but it is physically impossible to reach. Deep space hovers around 2.7 Kelvin, but these dilution refrigerators get hundreds of times colder than that. At such extreme cold, physics gets strange. Atoms can merge into a single “superatom,” liquids can crawl up the sides of walls, and electricity can flow with zero resistance. More importantly, when molecules slow down that much, scientists can peer into the quantum realm—the smallest scale of reality—where the normal rules of everyday physics break down.

Why cold matters for quantum computing