Summary form only given. With the impending redefinition of the SI second based on optical clocks, there is a need for new secondary optical frequency standards. Ideally these secondary standards will offer enhanced robustness, portability and high signal-to-noise ratios (SNR), to enable rapid and precise comparisons against primary standards. A clock based on a narrow optical transition, in atomic ions that are naturally trapped in a solid-state host crystal, offers the technological simplicity and large SNR to satisfy these requirements.Summary form only given. With the impending redefinition of the SI second based on optical clocks, there is a need for new secondary optical frequency standards. Ideally these secondary standards will offer enhanced robustness, portability and high signal-to-noise ratios (SNR), to enable rapid and precise comparisons against primary standards. A clock based on a narrow optical transition, in atomic ions that are naturally trapped in a solid-state host crystal, offers the technological simplicity and large SNR to satisfy these requirements.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)Jul 1, 20170 citations

Lattice-based optical clock using an even isotope of Yb

Zeb W. Barber, Chad Hoyt, J. E. Stalnaker +5 more

We describe progress toward an optical lattice clock based on an even isotope of Yb. The 1S0 → 3P0 clock resonance in 174Yb is accessed through a magnetically induced spectroscopic technique. Using ≈1mT static magnetic fields and ≈10 μW of probe light power we generate Rabi frequencies of several hertz. The narrow spectroscopic features that result (< 10 Hz FWHM) require a highly stabilized laser at the clock transition wavelength of 578 nm. We describe a new all solid-state laser system that shows hertz level stability. In order to cancel the slow drift of the cavity, spectroscopy is performed on the clock transition to provide feedback to the laser. Using a Ca neutral atom frequency standard as a reference oscillator,we show high stability and an effective method for investigating clock frequency shift systematics.We describe progress toward an optical lattice clock based on an even isotope of Yb. The 1S0 → 3P0 clock resonance in 174Yb is accessed through a magnetically induced spectroscopic technique. Using ≈1mT static magnetic fields and ≈10 μW of probe light power we generate Rabi frequencies of several hertz. The narrow spectroscopic features that result (< 10 Hz FWHM) require a highly stabilized laser at the clock transition wavelength of 578 nm. We describe a new all solid-state laser system that shows hertz level stability. In order to cancel the slow drift of the cavity, spectroscopy is performed on the clock transition to provide feedback to the laser. Using a Ca neutral atom frequency standard as a reference oscillator,we show high stability and an effective method for investigating clock frequency shift systematics.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEAug 29, 20073 citations

A thorium-229 optical nuclear clock with feedback loop

L. Toscani De Col, T. Riebner, I. Morawetz +25 more

The laser-accessible nuclear transition in the thorium-229 isotope has been identified as a promising candidate for the realization of an optical nuclear clock. Such a nuclear clock might rival or outperform current optical clocks based on electron-shell transitions in atoms or ions, is expected to be more robust against external perturbations, and provides enhanced sensitivity in clock-based tests of fundamental principles of physics. Here, we implement a thorium-229 nuclear clock by stabilizing a continuous-wave laser to the 148 nm nuclear transition with rapid feedback based on continuous absorption spectroscopy. The thorium-229 nuclei are embedded into a millimeter-sized, room temperature calcium fluoride crystal. A subharmonic of the 148 nm radiation is continuously compared to a Yb+ single-ion clock. The nuclear clock shows a simple shot-noise limited scaling of the fractional frequency instability of $3\cdot 10^{-12} \sqrt{τ/\text{s}}$ where $τ$ is the averaging time, approaching $10^{-15}$ instabilities over 1 day of continuous operation. Improvements of the instability by several orders of magnitude can be projected for future solid-state nuclear clocks. We use the nuclear clock to constrain models of ultralight dark matter by searching for periodic fluctuations and slow drifts in the nuclear transition energy, on time scales between 20 s and 1 day. Drawing benefit from the enhanced sensitivity of the thorium-229 transition, these constraints compete with the best atomic clocks concerning dark matter coupling to photons and go beyond previous measurements regarding coupling to the strong force and quarks.The laser-accessible nuclear transition in the thorium-229 isotope has been identified as a promising candidate for the realization of an optical nuclear clock. Such a nuclear clock might rival or outperform current optical clocks based on electron-shell transitions in atoms or ions, is expected to be more robust against external perturbations, and provides enhanced sensitivity in clock-based tests of fundamental principles of physics. Here, we implement a thorium-229 nuclear clock by stabilizing a continuous-wave laser to the 148 nm nuclear transition with rapid feedback based on continuous absorption spectroscopy. The thorium-229 nuclei are embedded into a millimeter-sized, room temperature calcium fluoride crystal. A subharmonic of the 148 nm radiation is continuously compared to a Yb+ single-ion clock. The nuclear clock shows a simple shot-noise limited scaling of the fractional frequency instability of $3\cdot 10^{-12} \sqrt{τ/\text{s}}$ where $τ$ is the averaging time, approaching $10^{-15}$ instabilities over 1 day of continuous operation. Improvements of the instability by several orders of magnitude can be projected for future solid-state nuclear clocks. We use the nuclear clock to constrain models of ultralight dark matter by searching for periodic fluctuations and slow drifts in the nuclear transition energy, on time scales between 20 s and 1 day. Drawing benefit from the enhanced sensitivity of the thorium-229 transition, these constraints compete with the best atomic clocks concerning dark matter coupling to photons and go beyond previous measurements regarding coupling to the strong force and quarks.

physics.atom-phCross-listedarXiv:2606.04997Jun 4, 2026

3\cdot 10^{-12} \sqrt{τ/\text{s}}

where

τ

is the averaging time, approaching

10^{-15}

instabilities over 1 day of continuous operation. Improvements of the instability by several orders of magnitude can be projected for future solid-state nuclear clocks. We use the nuclear clock to constrain models of ultralight dark matter by searching for periodic fluctuations and slow drifts in the nuclear transition energy, on time scales between 20 s and 1 day. Drawing benefit from the enhanced sensitivity of the thorium-229 transition, these constraints compete with the best atomic clocks concerning dark matter coupling to photons and go beyond previous measurements regarding coupling to the strong force and quarks.