Systematic evaluation of an atomic clock at 2 × 10−18 total uncertainty

TLDR

Optical lattice clocks currently set the record for stability and accuracy, driving advances in quantum control, fundamental constant tests, and relativity experiments. This study advances a many‑particle clock by employing a state‑of‑the‑art stable laser to unlock its full potential. The JILA 87Sr optical lattice clock reached 2.2 × 10⁻¹⁶ fractional stability at 1 s and, after reducing key systematic shifts, achieved a total fractional uncertainty of 2.1 × 10⁻¹⁸.

Abstract

The pursuit of better atomic clocks has advanced many research areas, providing better quantum state control, new insights in quantum science, tighter limits on fundamental constant variation, and improved tests of relativity. The record for the best stability and accuracy is currently held by optical lattice clocks. This work takes an important step towards realizing the full potential of a many-particle clock with a state-of-the-art stable laser. Our 87Sr optical lattice clock now achieves fractional stability of 2.2e-16 at 1 s. With this improved stability, we perform a new accuracy evaluation of our clock, reducing many systematic uncertainties that limited our previous measurements, such as those in the lattice ac Stark shift, the atoms' thermal environment, and the atomic response to room-temperature BBR. Our combined measurements have reduced the total uncertainty of the JILA Sr clock to 2.1e-18 in fractional frequency units.