Vienna and Beijing teams independently achieve world's first operating nuclear clocks

Two research teams working on opposite sides of the world have built the first functioning nuclear clocks, a milestone that physicists have pursued for nearly half a century. The Vienna team, led by Thorsten Schumm at TU Wien, and the Beijing team, led by Shiqian Ding at Tsinghua University, announced their achievements this week in papers published in Nature, describing devices that represent a fundamental leap beyond the atomic clocks that have defined precision timekeeping since 1949.

Despite the name, these clocks have nothing to do with nuclear power. Instead, they work by using powerful lasers to monitor how light interacts with the nucleus of an atom—specifically, thorium-229 atoms trapped inside solid calcium fluoride crystals. This is a crucial distinction from conventional atomic clocks, which track electrons orbiting an atom's outer shell. Because an atomic nucleus is vastly smaller and more tightly bound than the electron shell surrounding it, measuring time through nuclear transitions promises to achieve even greater precision than current technology allows.

The parallel breakthroughs are themselves significant. The two teams reached working clocks independently, using different experimental methods, which suggests the underlying concept is sound and not reliant on any single technical approach. Schumm's Vienna group has been pursuing this goal since 2008, while the researchers acknowledge that creating a nuclear clock was a dream physicists held for roughly fifty years. The fact that both teams succeeded simultaneously, without coordination, demonstrates that the path forward is not a dead end but a genuine frontier.

Yet both teams are candid about where the technology stands. The nuclear clocks are still far from their theoretical performance ceiling. The best conventional atomic clocks can run for billions of years while losing or gaining only a single second—a precision that has made possible everything from GPS satellites to fiber-optic communications networks. The new nuclear clocks do not yet surpass this standard, though the researchers believe they will once refinement continues. Schumm noted that the Vienna clock produces higher-quality thorium crystals with better optical properties, while the Beijing team has engineered a more powerful laser. Combining these strengths could yield a significantly improved device.

The practical applications are wide-ranging. Schumm envisions nuclear clocks transforming satellite-based navigation, data synchronization, surveying, and metrology—the science of measurement itself. Because these clocks could eventually be built smaller and more robust than current atomic clocks, they might replace existing technology in systems where size and durability matter. The Vienna team has already demonstrated that their clock can perform precision physics experiments; they used it to search for dark matter, one of the universe's most elusive components. The experiment did not detect dark matter, but the clock performed at the level of the best atomic clocks currently in use, proving its capability as a research instrument.

What makes this moment distinctive is not that the problem is solved but that it has moved from theoretical possibility to working reality. Two independent paths have converged on the same destination, suggesting that refinement and improvement are now engineering challenges rather than fundamental unknowns. The researchers are already thinking about how to combine the best features of each approach. The next phase is not invention but perfection—taking devices that work and making them work better, faster, and more reliably than anything that came before.