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Scientists in Vienna and Beijing have simultaneously unveiled the world's first working nuclear clocks. This monumental achievement promises to revolutionize fields from satellite navigation to fundamental physics.
Scientists in Vienna and Beijing have simultaneously unveiled the world's first working nuclear clocks. This monumental achievement promises to revolutionize fields from satellite navigation to fundamental physics.
Vienna and Beijing, October 8, 2026 – Humanity's quest for ever more precise timekeeping reached a monumental milestone today as independent teams of scientists in Vienna, Austria, and Beijing, China, simultaneously announced the successful creation of the world's first working nuclear clocks. This groundbreaking achievement, detailed in a pair of studies published concurrently in the journal Nature, ushers in a new epoch for metrology, poised to revolutionize fields from satellite navigation to fundamental physics.
For decades, the atomic clock has stood as the pinnacle of timekeeping accuracy, underpinning the intricate synchronization of our modern world. Yet, scientists have long theorized about an even more stable timekeeping device: the nuclear clock. Today, that theory has become reality, thanks to the dedicated efforts of researchers at the Vienna University of Technology (TU Wien) and Tsinghua University in Beijing. This parallel development highlights a "fierce but friendly global competition" that has ultimately advanced scientific frontiers on a global scale.
A nuclear clock is an atomic clock that uses photons from a nuclear isomeric transition as its reference frequency, instead of the atomic electron transition energy used by conventional atomic clocks. These clocks harness the incredibly stable oscillations within an atom's nucleus, rather than its electron shell, promising a leap in precision previously thought unattainable. Scientists predict that such clocks could achieve a time stability approaching 10^-19, a tenfold improvement over electron-based clocks.
The fundamental principle behind nuclear clocks lies in the fact that the atomic nucleus is significantly smaller than the atomic shell, by up to five orders of magnitude. This minuscule size renders the nucleus far less susceptible to external electromagnetic interference, such as magnetic and electric fields, which are the primary limiting factors for the stability of electron-based atomic clocks. This inherent robustness makes nuclear clocks ideal candidates for pushing the boundaries of time measurement.
The simultaneous realization of working nuclear clock prototypes in Vienna and Beijing marks a historic day for science, October 8, 2026. Both teams successfully built their clocks around the unique properties of thorium-229, specifically its metastable excited nuclear state known as the isomeric state. This particular isomer, Thorium-229m, is the lowest-energy nuclear isomer known, possessing an energy of 8.355733554021(8) eV, which makes its transitions accessible to laser excitation in the vacuum ultraviolet (VUV) region.
In Vienna, the team at TU Wien, led by Professor Thorsten Schumm, a co-author of the groundbreaking study, achieved this feat by embedding thorium-229 nuclei in solid-state calcium fluoride crystals. "The creation of a nuclear clock was something that physicists dreamt of for almost 50 years. In my team, we have been working towards this goal since 2008," stated Professor Schumm. He emphasized the significant advantage of using atomic nuclei, enabling higher precision in principle.
Concurrently, researchers at Tsinghua University in Beijing, under the leadership of physicist Shiqian Ding, also unveiled their fully functional thorium-229 nuclear clock. Dr. Ding highlighted that the independent development by both teams, using different experimental approaches, is "very encouraging because it shows that the concept is robust and not dependent on one particular technical implementation." The Beijing team's initial results reportedly demonstrated a stability approximately six times greater than the Vienna clock, indicating the potential for robust reproducibility.
This dual success underscores a remarkable convergence of scientific effort and ingenuity. While atomic clocks have been around since the 1950s, using elements like cesium or strontium to track electron transitions, these new nuclear clocks delve deeper, targeting jumps inside an atom's nucleus.
The significance of nuclear clocks extends far beyond merely building a "better clock." Their unprecedented precision promises to unlock new avenues of scientific exploration and technological advancement. Current atomic clocks, such as those based on cesium-133, define the second as 9,192,631,770 oscillations of the atom's electron in its ground state. These clocks are incredibly accurate, with the best able to keep time with an uncertainty of 1 second every 300 million years, or even up to 1 second in 100 million years for International Atomic Time (TAI) derived from hundreds of atomic clocks worldwide. However, nuclear clocks are poised to redefine this standard.
Scientists predict that more advanced nuclear clocks could reduce this uncertainty to just 1 second every billions of years, representing a tenfold improvement over current electron-based clocks. This leap in accuracy is primarily due to the nucleus's isolation from external perturbations. The nucleus, being about 100,000 times smaller than the atom, is far less sensitive to stray electric and magnetic fields that can subtly affect atomic clocks.
As Dr. Shiqian Ding noted, "moving the clock's tick from electrons to the nucleus mattered because the nucleus was much smaller than the atom and less disturbed by stray electric and magnetic fields. In the long term, this could allow nuclear clocks to reach extremely high accuracy."
The realization of the nuclear clock hinges on the peculiar properties of thorium-229. While exciting the nucleus usually requires enormous amounts of energy, thorium-229 is a rare exception with a uniquely low-energy isomeric transition. This low transition energy, estimated at around 8.4 eV, falls within the vacuum-ultraviolet (VUV) range, making it accessible to coherent laser control.
Both the Vienna and Beijing teams utilized this specific isotope, embedding it within calcium fluoride crystals. The basic idea involves a laser tuned to the precise frequency that causes the thorium nucleus to flip between two energy states. This laser then stabilizes the frequency of the thorium nuclei, creating an ultra-stable "tick."
The embedding of thorium-229 atoms in a VUV-transparent crystal such as CaF2 offers a crucial advantage: a large concentration of thorium nuclei within the crystal. This higher concentration leads to a considerably higher signal-to-noise ratio, thereby contributing to greater clock stability. The ability to use a solid-state system, rather than the bulky atomic trapping systems required by many optical atomic clocks, also paves the way for more compact and robust nuclear clocks.
The implications of nuclear clocks are vast and far-reaching, promising to enhance existing technologies and enable entirely new scientific endeavors.
While today's announcement marks a monumental success, the journey to fully optimized nuclear clocks is ongoing. Researchers acknowledge that the current prototypes, while functional, do not yet surpass the absolute best conventional atomic clocks in terms of long-term stability. For example, a recent prototype may drift by about one second every 30 million years, which is still about ten times worse than the best cesium clocks.
One of the significant challenges has been the precise characterization and control of the thorium-229 isomer, which requires specialized vacuum-ultraviolet (VUV) lasers. Developing stronger, more efficient VUV lasers and improving crystal growth techniques to produce ultra-pure, defect-resistant thorium-embedded crystals are crucial for enhancing performance. Blasting crystals with high-energy VUV lasers can damage the lattice structure, creating "color centers" that absorb laser light and shift the nuclear transition frequency, a problem that needs to be overcome for continuous operation.
Furthermore, the isotope thorium-229 is rare, radioactive, and costly to acquire in substantial quantities. However, advancements in methods like creating thin films of thorium tetrafluoride have shown promise in making nuclear clocks a thousand times less radioactive and more cost-effective, suggesting future devices could be more accessible and scalable.
Despite these challenges, the rapid progress is undeniable. As Professor Schumm noted, combining the strengths of the Vienna team's better thorium crystals and the Beijing team's stronger laser could lead to "a significantly better clock."
To appreciate the true potential of nuclear clocks, it's essential to understand how they compare to their atomic predecessors.
| Feature | Atomic Clocks (Conventional) | Nuclear Clocks (Thorium-229) |
|---|---|---|
| Timekeeping Mechanism | Electron transitions between energy levels. | Nuclear isomeric transitions within the nucleus. |
| Reference Element | Cesium-133, Strontium, Ytterbium, Lutetium. | Thorium-229m. |
| Susceptibility to External Fields | More sensitive to electric and magnetic fields. | Significantly less affected by external fields. |
| Current Accuracy (Best) | ~1 second in 300 million years (prototypes); 1 second in 100 million years (TAI) | ~1 second in 30 million years (prototypes, Oct 2026). |
| Projected Accuracy | Limited by electron shell environment. | ~1 second in billions of years (factor of 10 improvement). |
| Size/Portability | Often large, requiring vacuum chambers and cooling. | Potential for smartphone-sized, transportable devices. |
| Primary Limitation | External perturbations affecting electron states. | Challenges with laser technology and crystal degradation. |
The clear advantage lies in the intrinsic stability of the nucleus, shielded from environmental noise far more effectively than electron shells. This fundamental difference is what allows nuclear clocks to push the boundaries of timekeeping.
"This is an outstanding result," commented Dr. Victor Flambaum, a theoretical physicist at the University of New South Wales in Sydney, in June 2026, referring to the European team's work, and noting its implications for fundamental physics and the search for dark matter.
Professor Andrei Derevianko, whose theoretical work has been instrumental in the development of both atomic and nuclear clocks, highlighted the transformative potential in December 2025: "Nuclear clocks, when fully realized, can be unimaginably precise, more accurate than atomic clocks." He further envisioned "smartphone-sized, super-accurate clock that one can hold in your hand."
Echoing this sentiment, Professor Thorsten Schumm of TU Wien envisions applications "in areas such as satellite-based navigation, synchronisation of data transfer, surveying and metrology." The collaborative spirit, despite the independent research, has led to a synergy of components that promise even better clocks in the near future.
The successful creation of the world's first nuclear clocks by scientists in Vienna and Beijing marks a profound leap forward in human ingenuity. On this day, October 8, 2026, we stand at the threshold of a new era of ultra-precise timekeeping, one that promises not only to refine our technological capabilities but also to deepen our understanding of the fundamental laws governing the universe. While challenges remain in perfecting these devices, the foundational work has been laid. The ticking of these new nuclear clocks is not just counting seconds; it's counting down to a future of unprecedented scientific discovery and technological advancement.
Nuclear clocks derive their superior accuracy from using transitions within an atom's nucleus, rather than its electron shell, as the basis for timekeeping. The nucleus is much smaller and far less susceptible to external environmental perturbations like stray electric and magnetic fields, which can cause inaccuracies in atomic clocks. This inherent stability allows nuclear clocks to maintain precision over significantly longer periods.
Nuclear clocks are expected to have a transformative impact on technologies that rely on ultra-precise timing. This includes vastly improving the accuracy of satellite navigation systems (like GPS) to potentially centimeter-level precision, enhancing the stability and speed of global communication networks, and enabling more accurate remote sensing and surveying for various industries. Their potential for miniaturization could also lead to highly accurate, portable timekeeping devices.
Despite the breakthrough, key challenges include refining the laser technology to precisely control the nuclear transitions and improving the stability and optical properties of the thorium-229 crystals. Scientists are working on developing more robust crystals that can withstand intense vacuum-ultraviolet (VUV) laser exposure without degradation, ensuring continuous and stable operation. Overcoming these hurdles will be crucial for pushing nuclear clock performance beyond current atomic clock capabilities.
Beyond practical timekeeping, nuclear clocks offer an unparalleled tool for fundamental physics research. Their extreme sensitivity to minute variations makes them ideal for testing theories of relativity, searching for topological dark matter, and investigating whether fundamental constants of nature remain truly constant over time. By observing how these clocks behave under different conditions, scientists can gain new insights into the universe's most profound mysteries.
Featured image by Lukáš Lehotský on Unsplash
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