Using clocks to detect ultralight dark matter | UDaily

As the accuracy and portability of atomic clocks continue to improve, University of Delaware physicist Marianna Safronova and collaborators Yu-Dai Tsai of the University of California, Irvine and Joshua Eby of the University of Tokyo and the Kavli Institute for the Physics and the Mathematics of the Universe, want to put these precision watches at the service of the search for dark matter.

Scientists have been trying for decades to understand “dark matter,” the unknown essence that makes up about 85% of all matter in the universe. Its effects can be observed, but it has not yet been detected directly.

This proposal, published on Monday 5 December in natural astronomywould send two atomic clocks to the far reaches of the solar system to search for ultra-light dark matter, which has wave-like properties that could affect how the clocks work.

Atomic clocks, which tell the time by measuring the rapid oscillations of atoms, are already at work in space, enabling the Global Positioning System (GPS). Future space clocks could help spacecraft navigate and provide links to Earth clocks. Safronova has been among other proposals, including one released in July that would link Earth clocks to atomic clocks in orbit and test gravity. Placing atomic clocks in the variable-gravity environment of space could yield tests of gravity far more accurate – four orders of magnitude or 30,000 times more accurate – than is possible on Earth.

This proposal would send experiments that were performed on Earth closer to the sun than to Mercury, where there could be more dark matter to detect.

The work would be done by atomic, nuclear and molecular clocks which are still under development. They are often called “quantum sensors”.

“It was inspired by the Parker Solar Probe,” Safronova said, referring to NASA’s ongoing mission that has sent a spacecraft closer to the sun than any spacecraft before. The probe flew past the solar corona for the first time in 2021 and continues to circle closer and closer.

“It had nothing to do with sensors or quantum clocks,” she said, “but it showed that you could send a satellite very close to the sun, detect new conditions and make discoveries. is much closer to the sun than what we propose here.

NASA’s 2019 Deep Space Atomic Clock mission demonstrated the best atomic clock in space to date, Safronova said, but different types of clocks — based on much higher frequencies — have been developed over the 15 last years. Such “optical” clocks are orders of magnitude more accurate and will not lose even a second of time in billions of years.

With this type of technology now available on Earth, Safronova and her collaborators began talking about the type of questions that would be possible to study in space that cannot be done on Earth.

“It’s a nice synergy between a quantum expert and particle theorists,” said Tsai, lead author of the natural astronomy article, “and we’re working on new ideas at the intersection of these two areas.”

They stopped on this study of ultra-light dark matter, which scientists believe could form a huge halo-like region, bound to the sun.

“It has very specific properties and is very specific dark matter that is detectable by clocks,” Safronova said.

Such ultralight dark matter would cause the energies of atoms to oscillate, Safronova said, and it would change the way the clock works. This effect depends on the atoms used by the clock. Scientists are tracking observed differences in clocks to search for dark matter.

“What is observable is the ratio of these two clock frequencies,” she said. “This ratio should oscillate if such dark matter exists.”

All clocks mark time using some sort of repeating process — a swinging pendulum, for example, Safronova said. The atomic clock uses laser technology to manipulate and measure the oscillations of atoms. These oscillations are very fast. A clock based on strontium atoms, for example, “ticks” 430 trillion times per second, she said, and atomic clocks are far more accurate and stable than any mechanical device.

In a lab, these atomic clocks span a table or multiple tables, Safronova said, but portable atomic clocks have been developed that can fit in a van. NASA’s Deep Space Atomic Clock is even smaller – about the size of a toaster.

Nuclear clocks, which are based on nuclear energy levels rather than atomic energy levels, would be the best clock for this research, Safronova said, and she is involved in the project to build a prototype, funded by the European Research Council.

“We have portable clocks now and it’s fun to think about how you would send such high precision clocks into space and establish what great things we can do,” Safronova said.

As technology advances, more proposals and opportunities will emerge. NASA’s Artemis program, for example, will pioneer new research based on the Moon.

“There are a lot of things we can do on the Moon, like building telescopes and even gravitational wave detectors, enabling new science,” she said. “We want to learn a lot more about the moon first, for example its seismic activity.”

Studies using quantum sensors are part of the university’s new quantum science and engineering program, said Safronova, an interdisciplinary graduate program that was established earlier this year. Studies focus on understanding and exploiting the unusual behavior of particles and excitations governed by the laws of quantum mechanics.

Atomic clocks are important in the study of geodesy, for example, the study of the geometric shape, gravity, and orientation of the Earth in space.

“These can now detect a height difference of one centimeter,” Safronova said. “So they’re getting better and better.”

And as technology improves, new questions emerge.

“There’s a whole range of great things we can do in space,” Safronova said. “We are at the very, very beginning of this.”

About the researcher

Marianna S. Safronova is a professor in the Department of Physics and Astronomy at the University of Delaware. His research focuses on quantum technologies and the search for physics beyond the standard model of elementary particles and fields, the development of atomic and nuclear clocks and their applications, dark matter searches, the development of relativistic atomic codes of high precision and development of atomic data online. gate. She received her bachelor’s and master’s degrees in physics from Moscow State University and her doctorate in physics from the University of Notre Dame. Before joining the UD faculty in 2003, she did postdoctoral work at the University of Notre Dame and was a visiting scholar at the National Institute of Standards and Technology (NIST). She is a fellow of the American Physical Society (APS) and a member of the Journal of Quantum Science and Technology Editorial Committee.