Yasunobu Nakamura

A metal resonator, chilled to near absolute zero, listens to the radio noise of the universe. Amid the chaos of thermal fluctuations and electronics, a faint peak might emerge — the trace of an axion, a particle that could make up dark matter.

A whisper in a noisy room is nearly indistinguishable. A conventional amplifier adds its own noise and drowns out the weak sound. A quantum amplifier works differently: it amplifies the signal while adding almost no extra noise, like a perfect ear. But even such an ear has its own problems.

In the basement of the laboratory, an 8 tesla magnet hums. Inside it, like a bell in a bell tower, hangs a hollow copper cylinder tuned to a single note. If an axion, a dark matter particle, flies by, the cylinder responds with a faint ring. The trouble is that ordinary copper muffles this ring: at high frequencies, current flows only through a thin skin of the metal, and losses grow.

Picture a radio receiver with a single tuning knob that moves all of its internal coils at once, like one living organism. That is exactly how a new instrument for the search for the axion works, a particle that may fill galaxies with invisible mass. Inside a copper cylinder the height of a coffee can sit rods of aluminum oxide.