How do you house equipment so sensitive to external factors that a building’s windows and elevators affect its results? For Shimon Kolkowitz, the Roger Herst Professor of Physics, you spend a year and a half overseeing a state-of-the-art lab renovation that will enable some of the world’s most precise measurements.
Kolkowitz is now celebrating the start of his lab’s operations at UC Berkeley. The lab’s rooms, located in the Physics South Building, will house ultraprecise clocks capable of keeping time with 19 decimal places of accuracy to test the fundamental theories of physics. Berkeley’s physicists, astronomers, and quantum scientists hope the Kolkowitz Lab will reveal new insights into phenomena like dark matter, gravitational waves, time dilation, and general relativity.
“I'm very grateful to the university and excited about the space,” said Kolkowitz. “It’s a world-class laboratory, and we're going to do cutting-edge research that pushes the limits of measurements that use these quantum systems.”
Research-quality time measurement has become far more precise in the past few decades. Mechanical clocks and watches tell time with physical mechanisms that can only “tick” a few times per second. Modern electronics such as smartphones use quartz clocks that vibrate crystals at 32,768 times per second. Atomic clocks use lasers to force caesium-133 atoms to oscillate at a predictable rhythm of 10 billion times per second. Optical lattice clocks — like the one Kolkowitz designed — surpass all these previous methods by using strontium atoms that oscillate 400 trillion (or 400,000,000,000,000) times a second.
Optical lattice clocks look nothing like the mechanical clocks most people are familiar with. There are no rotating dials or numeric displays. Instead, lenses, mirrors, and cables bounce and shape laser beams across three large tables, ending in a magnetic chamber that traps a cloud of atoms cooled to one millionth of a degree Celsius above absolute zero.
The atoms can oscillate at slightly different rates based on subtle changes in their environment, and small temperature fluctuations or vibrations can cause delicate components to shift out of alignment. Protecting the Kolkowitz Lab’s sensitive experiments from outside influences required many safeguards, including:
Even the tiniest of movements can affect results. Einstein’s theory of general relativity predicts that gravity causes time to pass more rapidly for a clock that is higher off the ground. Kolkowitz and other researchers showed that atom clouds a mere one millimeter higher or lower tick at slightly different rates, resulting in a disagreement between the clocks of one second over 300 billion years. Correcting for this effect is important to the accuracy of global positioning systems (GPS), since the clocks in satellites tick faster than their counterparts on the ground.
Kolkowitz’s team is now building another optical lattice clock that will be lifted two meters higher in the same room. When complete, the researchers will use that exaggerated difference to determine if relativity behaves as expected.
“Our goal is to realize experiments with aspects of both quantum mechanics and relativity, see how they interact, and test things at their interface,” said Kolkowitz. “These experiments are some of the only experiments where that happens — where we have a quantum system with relativistic effects showing up.”
Einstein’s theory of general relativity focuses on gravity and is best seen in the relationship between massive objects like planets and black holes. Quantum mechanics, on the other hand, usually governs physics at the atomic and subatomic levels. Both theories have held up well to tests, but the interplay between the two is not well understood as they are fundamentally at odds with each other.
Left three photos: workers moved the three-table optical lattice clock into the Kolkowitz Lab in the fall of 2024. Rightmost photo: The magnetic chamber where lasers trap a cloud of cold strontium atoms, as seen by the bright dot in the middle. (Photos by Shimon Kolkowitz)
Kolkowitz hopes that optical lattice clocks can also detect a cloud of dark matter passing by, or identify gravitational waves, which are ripples in space-time formed by massive collisions of celestial objects. Either of these discoveries would break open a new area of science by providing evidence that has eluded the scientific community for many years.
Kolkowitz also hopes to partner with Professor Holger Mueller to test whether clouds of atoms in a quantum superposition — being at two different places simultaneously — tick at different rates. This unexplored area could revolutionize our understanding of how physical objects work.
Kolkowitz previously worked at the University of Wisconsin–Madison. The university was generous in allowing Kolkowitz’s team to continue running experiments on his optical lattice clock while his Berkeley lab was under construction. In the fall of 2024, workers packed the clock’s tables and drove them across the nation.
Kolkowitz and Ph.D. student Jonathan Dolde adjust the clock’s settings. (Photo by Alexander Rony)
Kolkowitz is relieved and excited now that his new lab at UC Berkeley is mostly operational. He considers himself lucky because he purchased most of his lab’s new equipment before tariffs raised prices. He similarly avoided COVID-era supply chain disruptions by a few months when building his lab at the University of Wisconsin–Madison. Since the equipment is so specific, there are few manufacturers, so shortages have delayed other labs’ research by months or even years.
This week, the Kolkowitz Lab put the finishing touches on its “diamond room,” where researchers will conduct experiments on defects in diamonds to improve the power of quantum sensors. With this milestone, the Kolkowitz Lab team has finished moving out of their temporary space in Birge Hall, which previously housed half of the group.
The Department of Physics recruited Kolkowitz thanks in part to a strong lab startup package and an endowed position: the Roger Herst Chair in Physics. These funds enable the extensive renovations necessary to do highly-specialized research and offer ongoing, flexible funding through the chair position. Since the department hired Kolkowitz, it has further expanded its quantum expertise with new faculty members.
“It's a really exciting time for quantum at Berkeley,” said Kolkowitz. “Berkeley is one of the strongest institutions in this area. We are hiring the very best people in this field. It's an amazing community, and it's only growing.”
“I have the best job in the world.”
