Single-Ion Atomic Clock with $3\times10^{-18}$ Systematic Uncertainty (1602.03908v1)

Abstract: We experimentally investigate an optical frequency standard based on the $^2S_{1/2} (F=0)\to {}^2F_{7/2} (F=3)$ electric octupole (\textit{E}3) transition of a single trapped $^{171}$Yb$^+$ ion. For the spectroscopy of this strongly forbidden transition, we utilize a Ramsey-type excitation scheme that provides immunity to probe-induced frequency shifts. The cancellation of these shifts is controlled by interleaved single-pulse Rabi spectroscopy which reduces the related relative frequency uncertainty to $1.1\times 10^{-18}$. To determine the frequency shift due to thermal radiation emitted by the ion's environment, we measure the static scalar differential polarizability of the \textit{E}3 transition as $0.888(16)\times 10^{-40}$ J m$^2$/V$^2$ and a dynamic correction $\eta(300~\text{K})=-0.0015(7)$. This reduces the uncertainty due to thermal radiation to $1.8\times 10^{-18}$. The residual motion of the ion yields the largest contribution $(2.1\times 10^{-18})$ to the total systematic relative uncertainty of the clock of $3.2\times 10^{-18}$.

• The paper demonstrates a single-ion 171Yb+ atomic clock utilizing an E3 transition and advanced interrogation techniques to achieve a record low systematic uncertainty.
• The clock achieves a total systematic uncertainty of 3.2 x 10^-18 by minimizing probe light shifts (1.1 x 10^-18) and thermal radiation effects (1.8 x 10^-18).
• This work pushes the boundaries of timekeeping precision, enabling applications in fundamental physics, telecommunications, and navigation, while paving the way for future clock improvements.

Single-Ion Atomic Clock with 3x10^-18 Systematic Uncertainty

The paper investigates an advanced optical frequency standard based on the $^2S_{1/2} (F=0)\to {}^2F_{7/2} (F=3)$ electric octupole (E3) transition of a single trapped $^{171}$Yb$^+$ ion. Leveraging the low sensitivity of this transition to external fields and the large mass of the ion, the paper aims to minimize systematic frequency uncertainties, leading to high precision in atomic clocks.

Key Contributions and Methodologies

The authors introduced an advanced interrogation scheme using Ramsey-type spectroscopy, which is resistant to probe-induced frequency shifts. This method, supported by interleaved single-pulse Rabi spectroscopy, allows for significant reduction of the relative frequency uncertainty due to probe light shifts to $1.1 \times 10^{-18}$.

The team determined the static scalar differential polarizability of the E3 transition as $0.888(16) \times 10^{-40}$ J m$^2$/V$^2$, with a dynamic correction factor of $\eta(300~\text{K})=-0.0015(7)$. With this measurement, the frequency uncertainty due to thermal radiation is reduced to $1.8 \times 10^{-18}$.

Results

The single-ion Yb$^+$ atomic clock demonstrates a total systematic uncertainty of $3.2 \times 10^{-18}$. This performance represents an improvement over previous optical clocks utilizing different transitions, such as $^{27}$Al$^+$ and neutral $^{87}$Sr, where residual ion motion and thermal radiation respectively impose higher uncertainties.

The robust methodologies employed—including the hyper-Ramsey spectroscopy (HRS) technique—illustrate the potential of utilizing narrow linewidth transitions to mitigate perturbations that have historically limited clock precision and accuracy.

Implications and Future Directions

This research substantially pushes the boundaries of timekeeping, providing a foundational technology component for ultra-precise time-measurement tools critical to applications requiring tight synchronization, such as global positioning systems (GPS), telecommunications, and fundamental physics experiments.

The high sensitivity of the $^{171}$Yb$^+$ $^2F_{7/2}$ state to variations in fundamental constants enables probing potential violations of Lorentz invariance and exploring the interaction with ultralight scalar dark matter.

Anticipated future advancements may focus on addressing residual motion and further optimizing the trapping methods, which could lead to even lower systematic uncertainty and enhanced clock stability. These improvements could further penetrate applications in fields such as relativistic geodesy and network synchronization.

Overall, this paper demonstrates the forefront of developing atomic clocks. It enhances understanding of systematic perturbation management and provides insights into the subtle interactions between probe light and atomic states.