Optical clock intercomparison with $6\times 10^{-19}$ precision in one hour

Understand

Improvements in atom-light coherence are foundational to progress in quantum information science, quantum optics, and precision metrology.

• Optical atomic clocks require local oscillators with exceptional optical coherence due to the challenge of performing spectroscopy on their ultra-narrow linewidth clock transitions.
• Advances in laser stabilization have thus enabled rapid progress in clock precision.
• A new class of ultrastable lasers based on cryogenic silicon reference cavities has recently demonstrated the longest optical coherence times to date.