Jiacheng Xie

Two dilution cryostats, each the size of a barrel, stand at opposite ends of the laboratory. Inside are superconducting circuits cooled to 50 millikelvin, a hundred times colder than interstellar space. Between them runs an ordinary optical fiber, a kilometer of glass thread carrying light.

A guitar string rings longer if you don't touch it too much. A resonator, a device that vibrates at a single frequency like a tuning fork, behaves in much the same way. A team of engineers made such a "tuning fork" from aluminum nitride, smaller than a grain of sand, and made it oscillate 16 billion times per second.