Inside a glass capsule the size of a pea, rubidium atoms float. A laser beam puts them into a special state — Rydberg — where the electron flies far from the nucleus, making the atom extraordinarily sensitive to external fields. When a weak electric field appears nearby, the atoms slightly change their response to a second, probing laser beam. This makes the field visible.
The new device picks up field oscillations with frequencies from 1 to 100 hertz — these are slow, almost static signals. Sensitivity reaches 0.2 millivolts per meter per second of averaging. For comparison: a battery in your pocket creates a field millions of times stronger, yet the sensor can distinguish such weak perturbations.
This "atomic antenna" could inspect circuit boards and microchips without touching them with a probe, listen to extremely low-frequency signals underwater and through the ground, and detect the approach of a person or a charged object. It could also study electrical processes in living cells and geophysical phenomena.
Rydberg atoms are so large that one such atom can be the size of a bacterium — its outer electron orbits far away, like a planet around a star.
In the series "The Expanse," sensors based on quantum states of atoms monitor a ship's condition without a single wire — similar to this technology.