Sharper Than Ever: MIT Physicists Refine Atomic Clock Precision

Vladan Vuletić with members of his Experimental Atomic Physics group. From left to right: Matthew Radzihovsky, Leon Zaporski, Qi Liu, Vladan Vuletić, and Gustavo Velez. Credit:Melanie Gonick, MIT

MIT physicists have developed a new method to reduce “quantum noise” in atomic clocks, significantly improving their stability and precision. This breakthrough could enable the creation of highly accurate, transportable optical atomic clocks.

Atomic clocks are the backbone of modern technology. From smartphones and online banking to GPS navigation, our daily life relies on their precision. These clocks measure time by tracking the natural oscillations—or “ticks”—of atoms. Today’s standard atomic clocks use cesium atoms, which tick over 10 billion times per second, monitored by lasers oscillating at microwave frequencies.

Next-generation atomic clocks use faster-ticking atoms, such as ytterbium, which oscillate at optical frequencies thousands of times higher than microwaves. If stabilized, optical atomic clocks can measure incredibly fine time intervals—up to 100 trillion ticks per second—offering unprecedented precision.

MIT researchers have now found a way to enhance optical clock stability by reducing quantum noise, a fundamental limitation that obscures atomic oscillations. They also discovered that an effect previously considered negligible—the interaction between the clock’s laser and the atoms—can be leveraged to further stabilize the system.

The team developed a technique called global phase spectroscopy, which harnesses a laser-induced “global phase” in ytterbium atoms and amplifies it using quantum entanglement. This approach doubles the precision of an optical atomic clock, allowing it to resolve nearly twice as many ticks per second compared with previous methods. Moreover, the precision is expected to improve further with larger numbers of atoms.

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In experiments, the researchers cooled and trapped hundreds of ytterbium atoms in an optical cavity formed by curved mirrors. By passing a laser through the cavity, they induced entanglement among the atoms, which reduced the uncertainty—or noise—between the laser’s ticks and the atoms’ oscillations. The laser effectively “inherits” the atomic ticks, but only if it remains sufficiently stable. The team found that subtle changes in the atoms caused by the laser—previously thought irrelevant—actually carry information about the laser frequency. By amplifying this effect, they could suppress quantum noise and achieve higher measurement precision.

“This method allows us to resolve much finer differences in optical frequencies than before,” said Vladan Vuletić, Lester Wolfe Professor of Physics at MIT. “It could help make optical atomic clocks transportable and deployable wherever precise timekeeping is needed.”

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Portable atomic clocks could revolutionize a range of scientific and technological applications, from detecting dark matter and dark energy to testing fundamental physics or even monitoring geophysical events like earthquakes.

By combining advanced quantum techniques with optical frequency standards, MIT researchers have set a new benchmark for timekeeping, opening the door to a future of stable, highly precise, and mobile atomic clocks.

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