Record Stability and Accuracy in a Strontium Optical Clock

Atomic clocks have revolutionized precision measurement. Each advancement in timekeeping, from pendulum clocks to quartz oscillators, from microwave atomic clocks to optical atomic clocks, opens the door to new areas of physics. State of the art atomic clocks based upon electronic transitions in the optical domain have recently aided in searches for dark matter [1], tested general relativity [2], and may soon redefine the SI second. I will discuss our work building the most stable and accurate atomic clocks using neutral strontium atoms. Using a laser locked to a single crystal silicon cavity, we interrogate a narrow electronic transition in a lattice confined sample of atoms. After careful measurement, we observe the gravitational redshift between atoms less than a millimeter apart [3]. With precise environmental control and engineering interactions between atoms, we have realized a record low fractional systematic uncertainty of 8e-19 [4]. Our most recent work is focused on extending the atomic coherence time, potentially opening the door to lifetime limited spectroscopy of the clock transition.

[1] CJ Kennedy et al., Phys. Rev. Lett. 125, 201302, 2020.

[2] Takamoto et al., Nat. Photonics 14, 411–415 (2020).

[3] Bothwell et al., Nature 602, 2022.

[4] Aeppli et al., Phys. Rev. Lett. 133, 023401, 2024.