MIT Physicists Double Precision of Atomic Clocks with 'Global Phase Spectroscopy'

In a significant advancement for timekeeping technology, physicists at the Massachusetts Institute of Technology (MIT) have developed a method that doubles the precision of optical atomic clocks. This breakthrough, announced on October 8, 2025, leverages a technique called "global phase spectroscopy" to reduce quantum noise, a fundamental limitation in measurement accuracy.

Atomic clocks are the cornerstone of modern timekeeping, relying on the consistent oscillations of atoms to measure time with exceptional accuracy. Traditional atomic clocks track cesium atoms oscillating over 10 billion times per second, using lasers synchronized at microwave frequencies. Next-generation optical atomic clocks aim to utilize atoms like ytterbium, which oscillate at even higher optical frequencies, potentially allowing for time measurements up to 100 trillion times per second.

A significant challenge in enhancing the precision of these clocks is quantum noise, an inherent uncertainty arising from the principles of quantum mechanics. This noise can obscure the pure oscillations of atoms, limiting the accuracy of time measurements. Addressing quantum noise is crucial for the development of more precise and stable atomic clocks.

The MIT research team, led by Professor Vladan Vuletić, developed a method called "global phase spectroscopy" to mitigate quantum noise. This approach involves inducing a "global phase" in a collection of ytterbium atoms using a laser. The global phase refers to a collective shift in the phase of the atomic ensemble, which, when measured, provides information about the laser's frequency relative to the atoms' natural oscillations. By amplifying this global phase effect through quantum entanglement—a phenomenon where particles become interconnected such that the state of one directly relates to the state of another—the researchers effectively reduced the measurement uncertainty caused by quantum noise.

In their experiments, the team cooled and trapped several hundred ytterbium atoms in a cavity formed by two curved mirrors. They then introduced a laser into the cavity, which interacted with the atoms, causing them to become entangled. This entanglement redistributed the quantum noise, resulting in a clearer and more measurable "tick" from the atoms. The application of global phase spectroscopy doubled the precision of the optical atomic clock, allowing it to discern twice as many atomic oscillations per second compared to previous configurations.

The enhancement in atomic clock precision achieved through global phase spectroscopy has several significant implications:

• Global Positioning System (GPS) Accuracy: Improved atomic clock precision can lead to more accurate GPS systems, benefiting navigation for both civilian and military applications.

• Telecommunications: Enhanced timekeeping can improve synchronization in telecommunications networks, leading to more efficient data transmission and reduced latency.

• Fundamental Physics Research: More precise atomic clocks can be used to test fundamental physics theories, such as the constancy of fundamental constants and the detection of dark matter and dark energy.

Additionally, the researchers anticipate that their method could enable the development of portable optical atomic clocks. Such transportable clocks could be deployed in various locations to measure phenomena like gravitational variations and seismic activity, potentially aiding in earthquake prediction.

Professor Vladan Vuletić, the Lester Wolfe Professor of Physics at MIT, emphasized the broader implications of their work:

"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."

This research was supported by several organizations, including the U.S. Office of Naval Research, the National Science Foundation, the U.S. Defense Advanced Research Projects Agency, the U.S. Department of Energy, the U.S. Office of Science, the National Quantum Information Science Research Centers, and the Quantum Systems Accelerator.

In 2020, the same MIT team demonstrated that quantum entanglement could improve atomic clock precision by reducing quantum noise. However, they were limited by the instability of the clock's laser. In 2022, they developed a "time reversal" technique to further amplify the difference between the laser and atomic tick rates. The current advancement builds upon these previous methods by applying them to optical atomic clocks operating at higher frequencies, achieving a significant reduction in quantum noise and doubling the clock's precision.

This breakthrough marks a significant step forward in the quest for ever more precise timekeeping, with wide-ranging implications for technology and fundamental science.