Atomic clocks play a significant role in keeping our digital infrastructure humming, but with our society’s ever-increasing computing needs, researchers are now developing a clock that can keep up with the future at up to 100 trillion ticks per second.
Not only that, such technology, based on a new technique developed by MIT scientists, could even lend physicists a hand in the ongoing search for some of the universe’s most elusive phenomena, such as dark matter.
GPS satellites, clocks on our phones, and interactions between computers all require precision time tracking, made possible by monitoring the oscillations of cesium atoms at 10 billion times a second. To upgrade this capability to meet the next generation of communications and computing infrastructure, MIT physicists have revealed a way to increase the stability of ytterbium-based optical clocks in a new paper published in Nature.
Quantum Noise
The greatest challenge in advancing the optical measurement technologies required for using ytterbium in an atomic clock is removing quantum noise, which muddies readings of the atom’s exact movements. In their attempt to mitigate this long-standing issue, the MIT team stumbled upon a long-overlooked effect that clock lasers have on atoms, which can be manipulated to stabilize the focused beams of light they produce.
Their new method uses the laser to manipulate quantum entanglement in ytterbium atoms, enabling the researchers behind the discovery to double the clocks’ precision. The MIT team envisions pushing even further with the addition of more atoms.
A long-term goal of the work is to develop a portable atomic clock that can be brought on-site to measure various phenomena directly, potentially helping physicists in the hunt for some of our universe’s most elusive mysteries.
“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,” said co-author Vladan Vuletić, the Lester Wolfe Professor of Physics at MIT.
“We think our method can help make these clocks transportable and deployable to where they’re needed.”
A History with Atomic Clocks
Vuletić has been working on atomic clocks for years, previously as part of a team that demonstrated a technique to improve precision through quantum entanglement back in 2020. Through quantum entanglement, the atoms were pushed into a more tightly correlated behavior pattern, helping to define the clock’s tick against random noise more clearly.
To produce the entanglement, the team cooled hundreds of ytterbium atoms and then trapped them between two curved mirrors. A laser beam shot into the cavity, bounced around the mirrors thousands of times, and continually reacted with any atoms in its path to generate a state of quantum entanglement.
While that work demonstrated a noise reduction, the laser’s instability was a severe limiting factor. They continued their work with the development of a technique they characterize as “time reversal,” where they entangle and then de-entangle the atoms to boost the tick signal.
Despite their advances, the microwave technologies the researchers were working on were incapable of achieving the high frequencies required to fully match the intense speeds of ytterbium atoms.
“When you have atoms that tick 100 trillion times per second, that’s 10,000 times faster than the frequency of microwaves,” Vuletić says. “We didn’t know at the time how to apply these methods to higher-frequency optical clocks that are much harder to keep stable.”
Laser Time Reversal
To bridge the gap, the team found a method of applying the time reversal technique to optical atomic clocks by utilizing a laser that oscillates close to the optical frequency of the entangled atoms. A laser used to observe these atoms will inherit their ticking, but to maintain synchronization, it requires high stability. Previously, researchers believed that the phenomenon had no impact on atomic clocks’ operations. It wasn’t until the MIT team that anyone realized the light penetrating entangled atoms could increase their energy, allowing them to return to normal and retain a memory of the event.
“One might think we’ve done nothing,” Vuletić says. “You get this global phase of the atoms, which is usually considered irrelevant. But this global phase contains information about the laser frequency.”
Their work identified that merely subjecting the atoms to the laser left a lasting and measurable change, even after they returned to their original energy state.
“Ultimately, we are looking for the difference of laser frequency and the atomic transition frequency,” explains co-author Liu. “When that difference is small, it gets drowned by quantum noise. Our method amplifies this difference above this quantum noise.”
During laboratory tests, the team successfully doubled the precision of an optical atomic clock using their new technique. While running atomic clocks remains a significant technical challenge, the team’s work provides a new tool that will advance efforts toward the design of stable, transportable atomic clocks.
The paper, “Quantum-Amplified Global-Phase Spectroscopy on an Optical Clock Transition,” appeared in Nature on October 8, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.