A nuclear clock synchronized to 229Th
Abstract
Atomic clocks have made time and frequency the most precisely measured quantities in physics, progressing from microwave standards that realize the SI second to optical clocks with unprecedented precision. A nuclear clock transfers the frequency reference from an electronic to a nuclear transition, and the uniquely low-lying, laser-accessible isomeric transition in 229Th currently offers the most practical route to compact, robust timekeeping and sensitive tests of fundamental physics. Realizing such a clock requires turning spectroscopy of the 229Th nuclear resonance into a stable discriminator for steering a traceable oscillator. Here we demonstrate a 229Th nuclear clock by stabilizing a continuous-wave, narrow-linewidth 148.4-nm vacuum-ultraviolet (VUV) laser to a resolved, weakly temperature-sensitive nuclear transition in 229Th:CaF2 crystals. A $10−μ\mathrm{W}$ VUV source generated by four-wave mixing in cadmium vapour and phototube-based frequency-modulation absorption readout provide a fast, high-signal-to-noise nuclear discriminator. The clock reaches a fractional frequency instability of 5×10−13/√(τ/s) for averaging time τ. Clock-transition frequencies measured in two independently fabricated crystals agree at the 10−13 level and are consistent with previous VUV-comb measurements on other 229Th:CaF2 crystals. These results establish laser-addressed nuclei as operational clock references and provide a reproducible solid-state platform for compact nuclear clocks, nuclear quantum sensors and precision tests of fundamental physics.
Related
- A nuclear clock synchronized to ²²⁹Th.
- A solid-state nuclear clock based on VUV absorption spectroscopy of 229Th
- Origin of the inhomogeneous linewidth in a solid state 229Th:CaF2 nuclear clock
- A thorium-229 optical nuclear clock with feedback loop.
- Synchronized Spin Trajectories under Collective Weak Measurements
BibTeX
@misc{huang2026nuclear,
title = {{A nuclear clock synchronized to $^229$Th}},
author = {Beichen Huang and Gaowei Yan and Qi Xiao and Wenhao Bu and Chengchun Zhao and Zhen Zhang and Chao Yan and Zhi-Ang Chen and Peixiong Zhang and Gleb Penyazkov and Zhenhai Zhan and Lingfeng Yan and Yuefei Wang and Lin Li and Shanming Li and Dapeng Jiang and Xiaobo Qian and Xuegang Liu and Qiange He and Taoxiang Sun and Haochen Tian and Bingkun Lu and Ningyuan Ma and Juxian Li and Yanzhang Wu and Qiaorui Gong and Yuxiang Li and Haoyu Shi and Xiangliang Li and Longsheng Ma and Shining Zhu and Yuxiang Mo and Jun Lin and Li You and Yige Lin and Xibo Zhang and Yin Hang and Liangbi Su and Shiqian Ding},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.08870},
eprint = {2606.08870},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.08870},
}
RIS
TY - UNPB
TI - A nuclear clock synchronized to ^229Th
AU - Beichen Huang
AU - Gaowei Yan
AU - Qi Xiao
AU - Wenhao Bu
AU - Chengchun Zhao
AU - Zhen Zhang
AU - Chao Yan
AU - Zhi-Ang Chen
AU - Peixiong Zhang
AU - Gleb Penyazkov
AU - Zhenhai Zhan
AU - Lingfeng Yan
AU - Yuefei Wang
AU - Lin Li
AU - Shanming Li
AU - Dapeng Jiang
AU - Xiaobo Qian
AU - Xuegang Liu
AU - Qiange He
AU - Taoxiang Sun
AU - Haochen Tian
AU - Bingkun Lu
AU - Ningyuan Ma
AU - Juxian Li
AU - Yanzhang Wu
AU - Qiaorui Gong
AU - Yuxiang Li
AU - Haoyu Shi
AU - Xiangliang Li
AU - Longsheng Ma
AU - Shining Zhu
AU - Yuxiang Mo
AU - Jun Lin
AU - Li You
AU - Yige Lin
AU - Xibo Zhang
AU - Yin Hang
AU - Liangbi Su
AU - Shiqian Ding
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2606.08870
UR - https://arxiv.org/abs/2606.08870
AB - Atomic clocks have made time and frequency the most precisely measured quantities in physics, progressing from microwave standards that realize the SI second to optical clocks with unprecedented precision. A nuclear clock transfers the frequency reference from an electronic to a nuclear transition, and the uniquely low-lying, laser-accessible isomeric transition in ^229Th currently offers the most practical route to compact, robust timekeeping and sensitive tests of fundamental physics. Realizing such a clock requires turning spectroscopy of the ^229Th nuclear resonance into a stable discriminator for steering a traceable oscillator. Here we demonstrate a ^229Th nuclear clock by stabilizing a continuous-wave, narrow-linewidth 148.4-nm vacuum-ultraviolet (VUV) laser to a resolved, weakly temperature-sensitive nuclear transition in ^229Th:CaF_2 crystals. A $10−μ\mathrm{W}$ VUV source generated by four-wave mixing in cadmium vapour and phototube-based frequency-modulation absorption readout provide a fast, high-signal-to-noise nuclear discriminator. The clock reaches a fractional frequency instability of 5×10^−13/√(τ/s) for averaging time τ. Clock-transition frequencies measured in two independently fabricated crystals agree at the 10^−13 level and are consistent with previous VUV-comb measurements on other ^229Th:CaF_2 crystals. These results establish laser-addressed nuclei as operational clock references and provide a reproducible solid-state platform for compact nuclear clocks, nuclear quantum sensors and precision tests of fundamental physics.
ER -