The Royal Swedish Academy of Sciences on Tuesday awarded the 2025 jointly to , and , “for the discovery of macroscopic quantum mechanical tunneling and energy quantization in an electric circuit.”

Clarke, a professor emeritus of physics at the University of California, Berkeley, collaborates with the at the 91̽��. ADMX scans for evidence of dark matter from beneath the Seattle campus, in a cold dark box surrounded by a powerful magnetic field. The experiment is managed by the U.S. Department of Energy’s and it hinges on technology designed by Clarke.

“I was elated upon hearing the news about John. Simply elated,” said , a 91̽��professor emeritus of physics and lead scientist at ADMX.

The three laureates were recognized for that captured two quantum mechanical properties at the visible scale. Clarke’s brainchild, which caught Rosenberg’s attention 25 years ago, is a Superconducting Quantum Interference Device, or SQUID, which can make ultrasensitive measurements.

“John Clarke first got involved with ADMX around 2000,” Rosenberg recalled. “To this day, he remains a much-loved ADMX collaborator.”

The relationship began when ADMX organized a workshop at Lawrence Berkeley Laboratory to brainstorm solutions to a technical issue the researchers had encountered. The way the experiment searches for dark matter is akin to a radio searching for a station, but instead of music, it is looking for axions — the particles theorized to make up dark matter.

Detecting axions requires amplifying very, very quiet microwaves. At the time, the group only had access to noisy electronic amplifiers, which were drowning out the very signal they sought to capture. At the workshop, Clarke presented a SQUID amplifier as a potential solution.

“We considered all kinds of alternative technologies, but none fit the bill,” Rosenberg said. “The SQUID amplifiers were indeed the breakthrough we needed.”

Clarke joined ADMX and brought the amplifiers with him. , a 91̽��professor of physics and co-spokesperson for ADMX, was a postdoc at the time.

“The SQUID amplifiers gave us the sensitivity necessary to do a search,” Rybka said. “We’ve been operating for years and years and have only explored a fraction of the space, but we couldn’t have even started without these amplifiers.”

ADMX is still using an iteration of Clarke’s original amplifier, improved upon by his students over the years. Still, the “big transition,” was moving to the SQUID amplifier, and that is just one example of how this technology can revolutionize an experiment.

“The laureates moved the field of particle physics from classical measurement to quantum sensing,” Rybka said. “It makes stuff that used to just be on the blackboard — quantum mechanics — experimentally accessible and even useful. In my opinion, you wouldn’t have modern quantum computers without the work done by this group.”

Forty years ago, scientists theorized a new kind of low-mass particle that could solve one of the enduring mysteries of nature: what dark matter is made of. Now a new chapter in the search for that particle has begun.

This week, the (ADMX) unveiled a new result, in the journal , that places it in a category of one: it is the world’s first and only experiment to have achieved the necessary sensitivity to “hear” the telltale signs of dark matter axions. This technological breakthrough is the result of more than 30 years of research and development, with the latest piece of the puzzle coming in the form of a quantum-enabled device that allows ADMX to listen for axions more closely than any experiment ever built.

ADMX is based at the 91̽�� and managed by the U.S. Department of Energy’s . This new result, the first from the second-generation run of ADMX, sets limits on a small range of frequencies where axions may be hiding, and sets the stage for a wider search in the coming years.

“This result signals the start of the true hunt for axions,” said Fermilab’s Andrew Sonnenschein, the operations manager for ADMX. “If dark matter axions exist within the frequency band we will be probing for the next few years, then it’s only a matter of time before we find them.”

One theory suggests that the dark matter that holds galaxies together might be made up of a vast number of low-mass particles, which are almost invisible to detection as they stream through the cosmos. Efforts in the 1980s to find this particle, named the axion by theorist Frank Wilczek, currently of the Massachusetts Institute of Technology, were unsuccessful, showing that their detection would be extremely challenging.

ADMX is an axion haloscope — essentially a large, low-noise, radio receiver, which scientists tune to different frequencies and listen to find the axion signal frequency. Axions almost never interact with matter, but with the aid of a strong magnetic field and a cold, dark, properly tuned, reflective box, ADMX can “hear” photons created when axions convert into electromagnetic waves inside the detector.

“If you think of an AM radio, it’s exactly like that,” said , co-spokesperson for ADMX and assistant professor of physics at the 91̽��. “We’ve built a radio that looks for a radio station, but we don’t know its frequency. We turn the knob slowly while listening. Ideally we will hear a tone when the frequency is right.”

This detection method, which might make the “invisible axion” visible, was invented by Pierre Sikivie of the University of Florida in 1983, as was the notion that galactic halos could be made of axions. Pioneering experiments and analyses by a collaboration of Fermilab, the University of Rochester and the U.S. Department of Energy’s Brookhaven National Laboratory, as well as scientists at the University of Florida, demonstrated the practicality of the experiment. This led to the construction in the late 1990s of a large-scale detector at the U.S. Department of Energy’s Lawrence Livermore National Laboratory that is the basis of the current ADMX.

It was only recently, however, that the ADMX team has been able to deploy superconducting quantum amplifiers to their full potential enabling the experiment to reach unprecedented sensitivity. Previous runs of ADMX were stymied by background noise generated by thermal radiation and the machine’s own electronics.

Fixing thermal radiation noise is easy: a refrigeration system cools the detector down to 0.1 Kelvin (roughly -460 degrees Fahrenheit). But eliminating the noise from electronics proved more difficult. The first runs of ADMX used standard transistor amplifiers. Then, the researchers connected with John Clarke, a professor at the University of California Berkeley, who developed a quantum-limited amplifier for the experiment. This much quieter technology, combined with the refrigeration unit, reduces the noise by a significant enough level that the signal, should ADMX discover one, will come through loud and clear.

“The initial versions of this experiment, with transistor-based amplifiers would have taken hundreds of years to scan the most likely range of axion masses. With the new superconducting detectors we can search the same range on timescales of only a few years,” said Gianpaolo Carosi, co-spokesperson for ADMX and scientist at Lawrence Livermore National Laboratory.

“This result plants a flag,” said , professor of physics at the 91̽�� and chief scientist for ADMX. “It tells the world that we have the sensitivity, and have a very good shot at finding the axion. No new technology is needed. We don’t need a miracle anymore, we just need the time.”

ADMX will now test millions of frequencies at this level of sensitivity. If axions are found, it would be a major discovery that could explain not only dark matter, but other lingering mysteries of the universe. If ADMX does not find axions, that may force theorists to devise new solutions to those riddles.

“A discovery could come at any time over the next few years,” said scientist Aaron Chou of Fermilab. “It’s been a long road getting to this point, but we’re about to begin the most exciting time in this ongoing search for axions.”

The ADMX collaboration includes scientists at Fermilab, the 91̽��, Lawrence Livermore National Laboratory, Pacific Northwest National Laboratory, Los Alamos National Laboratory, the National Radio Astronomy Observatory, the University of California at Berkeley, the University of Chicago, the University of Florida and the University of Sheffield. This research is supported by the U.S. Department of Energy Office of Science, the Heising-Simons Foundation and research and development programs at the U.S. DOE’s Lawrence Livermore National Laboratory and the U.S. DOE’s Pacific Northwest National Laboratory.

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For more information, contact Sonnenschein at 630-840-2883 or sonnenschein@fnal.gov and Rybka at 206-543-2797 or grybka@uw.edu.

This is a joint  by Fermilab and the 91̽��.