Every elementary particle has its own rotation — spin. These tiny magnetic spinning tops constantly tremble, generating a faint noise. Hearing it is hindered by the din of light used in detectors. But in a diamond with artificial defects, glowing NV centers, scientists found a loophole. Nitrogen atoms near the defects act like stable 'recorders': their nuclei record the trembling of electron spins, ignoring the optical cacophony.

Repeated readout using spectroscopy allowed the useful whisper to accumulate and reduced overall noise by 3.8 decibels — approaching the fundamental quantum limit. For the first time, correlations between spins appeared without distortion: how they 'talk' to each other. This opens the era of quantum sensors with unprecedented sensitivity. For example, such defects are already able to detect the magnetic field of a single protein molecule, and operate inside a living cell. In perspective — squeezing of spin states for even more precise measurements.