![\"Th-229](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/03\/d41586-026-00848-7_52198526.jpg\"\/)
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Researchers are attempting to build the world\u2019s first nuclear clock. This is a view inside the vacuum chamber that holds crystals doped with the isotope thorium-229, which can be excited by a laser.Credit: Ye Labs\/JILA\/NIST\/University of Colorado<\/p>\n
Denver, Colorado<\/p>\n
Physicists are getting closer to creating a long-sought \u2018nuclear clock\u2019<\/a>. This device would keep time by measuring energy transitions in the nuclei of atoms and could become the most precise clock on the planet. <\/p>\n Decades ago, scientists predicted that the isotope thorium-229 could be used in such a clock, but they couldn\u2019t pin down its unusual nuclear energy transition. That feat, achieved with a laser in 2024<\/a>, started the countdown to a nuclear clock.<\/p>\n \u2018Nuclear clock\u2019 breakthrough paves the way for super-precise timekeeping<\/p>\n <\/a><\/p>\n Now, such a clock is \u201cway closer than people think\u201d, says Eric Hudson, a physicist at the University of California, Los Angeles, who is working on one. \u201cYou\u2019ll see nuclear-clock measurements in 2026, I\u2019m sure.\u201d<\/p>\n Nearly a dozen research teams spread across China, Europe, Japan and the United States are closing in on assembling the components of such a clock, including a source of thorium-229 \u2014 which is radioactive \u2014 and a powerful continuous-wave ultraviolet laser to excite the energy transition. At the American Physical Society (APS) Global Physics Summit in Denver, Colorado, this week, researchers provided updates on their progress, including details of laser development.<\/p>\n Claire Cramer, the executive director of quantum science at the University of California, Berkeley, who was in attendance, expressed optimism about the potential of solid-state nuclear clocks: \u201cThis is a really, really promising technology for commercial applications.\u201d<\/p>\n That\u2019s because nuclear clocks could be resilient to noise and have a compact design for use outside the laboratory. They might also surpass the precision of optical atomic clocks, the field\u2019s current top timekeepers, which lose only one second every 40 billion years.<\/p>\n Laser jockeying<\/p>\n Timekeeping, whether in a pocket watch or a physics laboratory, boils down to counting rapid, regular events \u2014 the \u2018ticks\u2019 in any clock. In optical atomic clocks, these events are the hopping of electrons in an atom between a ground and excited energy state. A laser with a wavelength in the 350- to 750-nanometre range (the visible, or optical, part of the electromagnetic spectrum) excites this transition, which can \u2018tick\u2019 trillions of times per second.<\/p>\n Countdown to a nuclear clock: a three minute guide<\/p>\n <\/a><\/p>\n By contrast, a nuclear clock would count transitions between nuclear states of thorium-229. These have the same number of protons and neutrons, but different energies depending on how the particles are squeezed together in the nucleus.<\/p>\n For half a century, the precise energy of the thorium-229 transition remained uncertain. Several independent research groups began to close in on an answer a few years ago1<\/a>. The search culminated in a 2024 experiment2<\/a> led by Chuankun Zhang, a physicist now at the California Institute of Technology in Pasadena, and Jun Ye, a physicist at JILA research institute in Boulder, Colorado. Using a frequency comb \u2014 a laser with about 30 million frequencies that can hit a crystal simultaneously \u2014 Zhang, Ye and their colleagues pinpointed the transition with ultra-high precision. To access it in a functioning nuclear clock, however, scientists now need a powerful and stable continuous-wave laser with an ultraviolet wavelength of around 148 nanometres. And no such laser has been made.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/03\/d41586-026-00848-7_27722810.jpg\"\/)
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