- MIT physicists doubled optical atomic clock precision using a quantum effect others had dismissed.
- The "global phase" of laser-entangled atoms encodes hidden frequency data no one had exploited before.
- Precision scales with atom count, so larger clocks could push accuracy even further.
Optical atomic clocks face a measurement paradox: quantum noise drowns out the very frequencies they are designed to track.
MIT physicists solved it by tuning the ticking of atoms and applying an effect which had been dismissed as irrelevant for atomic clock precision.
These next-generation timepieces rely on ytterbium atoms that tick 100 trillion times per second - 10,000 times faster than the cesium atoms in today's atomic clocks. The precision should be extraordinary, but quantum mechanics creates uncertainty that obscures the atoms' pure oscillations.
Key figure
100 ms
maximum drift across 13.8 billion years, if the new method is applied to today's best atomic clocks
The Effect Everyone Dismissed
When laser light passes through quantum-entangled atoms, it causes them to jump to higher energy states before settling back to their original positions. The atoms retain memory of the journey.
"One might think we've done nothing," says Vladan Vuletić, the Lester Wolfe Professor of Physics at MIT. "You get this global phase of the atoms, which is usually considered irrelevant. But this global phase contains information about the laser frequency."
What is global phase?
When laser light interacts with a group of atoms, it shifts the quantum state of each atom by the same amount – a shift called the global phase. Because every atom changes together, the effect cancels out in most measurements and was long treated as meaningless. The MIT team showed that this shared shift actually encodes the exact frequency of the laser, turning a discarded quantity into a precision signal.
Scientists had assumed this "global phase" effect was inconsequential to atomic clock operation. The MIT team realized it was actually a signal hiding in what everyone thought was noise.
The breakthrough came from recognizing that the magnitude of this phase change depends precisely on the laser's frequency - the very measurement atomic clocks need to make.
Why Earlier Solutions Were Not Enough
In 2020, Vuletić's team demonstrated that quantum entanglement could improve atomic clock precision by redistributing measurement uncertainty among correlated atoms. Their 2022 work added "time reversal" techniques that amplified the difference between laser and atom tick rates.
But those methods still used traditional microwave frequencies - like lifting dust from a painting, then photographing it with a low-resolution camera.
"When you have atoms that tick 100 trillion times per second, that's 10,000 times faster than the frequency of microwaves," Vuletić explains. "We didn't know at the time how to apply these methods to higher-frequency optical clocks that are much harder to keep stable."
The challenge was stabilizing lasers at optical frequencies. Microwave-based methods couldn't harness the full potential of ytterbium's rapid oscillations.
What Precision at This Scale Reveals
The team's new approach, called "global phase spectroscopy," doubles the precision of optical atomic clocks. The method enables clocks to discern twice as many ticks per second compared to the same setup without the technique.
«We saw that we can now resolve nearly twice as small a difference in the optical frequency or, the clock ticking frequency, without running into the quantum noise limit,» saus first author Leon Zaporski.
But here's what makes this discovery intriguing beyond the technical achievement: the precision should increase steadily with the number of atoms in the clock. More atoms means stronger signal amplification above the quantum noise threshold.
The advance addresses a limitation that had frustrated researchers for years - how to make optical atomic clocks stable enough for transport. Current versions require laboratory conditions, but the new method could enable portable devices.
With these clocks, people are trying to detect dark matter and dark energy, and test whether there really are just four fundamental forces, and even to see if these clocks can predict earthquakes.
Vladan Vuletić
If atomic clocks were running since the universe began 13.8 billion years ago, the most precise versions today would only be off by half a second. With this new method applied to state-of-the-art designs, that error would shrink to less than 100 milliseconds across cosmic time.
What else are we dismissing as irrelevant noise that might actually be the signal we need?
Fact Check: Claim-by-Claim Verification Verified
All claims verified against MIT press releases and prior published work. Quotes, attributions, and technical descriptions confirmed. Frequency figures use MIT's own rounded approximations.
Commentary
- The "100 trillion" and "10,000 times" figures are rounded approximations from MIT's press release, not the exact ytterbium frequency (~518 THz, which is ~56,000x cesium).
- The 100ms cosmic drift figure is illustrative; exact absolute stability depends on the specific clock implementation.
Sources used for verification
Academic/Peer-reviewed:
- MIT physicists improve atomic clocks' precision - news.mit.edu
Other reliable sources:
- Vladan Vuletić faculty page - physics.mit.edu
- 2020 entanglement work - news.mit.edu
- 2022 time reversal work - news.mit.edu
Fact-checked by Perplexity Sonar Pro on 2026-03-15
