An orchestra without a conductor: each musician hears only their neighbor and is slightly late or early. In ordinary atomic clocks, the picture is similar — atoms oscillate, but their rhythm is disrupted by thermal jitter, limiting timekeeping accuracy.
However, a group of physicists has managed to turn this flaw into a feature. They placed a cloud of one hundred thousand strontium atoms between two mirrors, an optical cavity, and illuminated it with a laser. The light bouncing between the mirrors makes the atoms "feel" each other. If an atom falls out of the common rhythm, it loses energy slightly faster than its neighbors and adjusts. This mechanism, called dissipation (energy scattering), usually destroys order, but here it acts like an invisible conductor. As a result, the uncertainty of the collective rhythm is squeezed — physicists speak of "spin squeezing." In the experiment, they managed to reduce quantum noise by more than 300 times compared to the standard limit. That's roughly like a hundred experts' divergent opinions suddenly collapsing into a unanimous verdict.
The trickiest part is operating in a regime where the light doesn't have time to "settle" between atoms. Previously, it was thought that for such a trick, photons needed to live in the cavity for a very short time, otherwise they would entangle the picture. The authors showed that by smoothly tuning the laser's frequency and power, the system can find a stable regime with a small number of photons, where parasitic effects are suppressed. At the end of the procedure, the quantum entanglement can be carefully transferred to long-lived atomic states simply by turning off the laser. So the orchestra continues to play in harmony even after the conductor leaves.
This approach requires no exotic conditions and can be implemented in existing laboratories. It opens the way to clocks that could test whether fundamental constants change over time, search for dark matter through glitches in time flow, and improve satellite navigation to centimeter-level accuracy.
Strontium-based atomic clocks are so accurate that if they had been running since the Big Bang, they would have drifted by less than one second by today.
In Liu Cixin's novel "The Dark Forest," ultra-precise clocks are used to synchronize attacks on starships scattered light-years apart — a tiny error in time results in a miss by millions of kilometers.