A Fermi-degenerate three-dimensional optical lattice clock (1702.01210v2)

Abstract: Strontium optical lattice clocks have the potential to simultaneously interrogate millions of atoms with a high spectroscopic quality factor of $4 \times 10^{-17}$. Previously, atomic interactions have forced a compromise between clock stability, which benefits from a large atom number, and accuracy, which suffers from density-dependent frequency shifts. Here, we demonstrate a scalable solution which takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional optical lattice to guard against on-site interaction shifts. We show that contact interactions are resolved so that their contribution to clock shifts is orders of magnitude lower than in previous experiments. A synchronous clock comparison between two regions of the 3D lattice yields a $5 \times 10^{-19}$ measurement precision in 1 hour of averaging time.

• The paper demonstrates a Fermi-degenerate 3D optical lattice clock that reduces density-dependent frequency shifts.
• The methodology employs a degenerate Fermi gas in a Mott-insulating regime with over 10^13 atoms/cm³ to optimize timekeeping precision.
• The study manages AC Stark shifts through tuned lattice light and polarization strategies, achieving measurement precision at the 5×10⁻¹⁹ level.

Insights into a Fermi-Degenerate Three-Dimensional Optical Lattice Clock

The paper "A Fermi-degenerate three-dimensional optical lattice clock" presents a significant advancement in the development of optical lattice clocks, focusing on the integration of Fermi-degenerate gases in a three-dimensional (3D) lattice structure. Such configurations maximize atomic density while addressing issues related to density-dependent frequency shifts, which have long challenged optical clock stability and accuracy. This paper details a systematic approach to managing atomic interactions, ensuring precision in timekeeping systems.

Optical lattice clocks have been at the forefront of precision measurement, but the limitations of one-dimensional (1D) systems become evident with increasing demands for suppression of atomic interactions. The transition to a 3D lattice represents an effort to mitigate these interactions by utilizing a Mott-insulating regime with a degenerate Fermi gas, effectively separating atoms to reduce frequency shifts due to collisions. The use of strontium—the paper's choice for atomic species—provides a deep insight into controlling and optimizing spectroscopic properties beyond current limitations.

In their experimental setup, the authors describe the loading of a two-spin state degenerate Fermi gas into a 3D lattice, suppressing double occupancy and resolvable two-body interactions by orders of magnitude compared to non-interacting gases. Enhanced interaction energy ensures that any remaining interactions do not interfere with clock transitions, allowing for high-density operations with over $10^{13}$ atoms/cm$^3$, an unprecedented figure in lattice clock experiments.

Crucially, the paper explains how the architecture of the 3D lattice allows for the management of AC Stark shifts by tuning the lattice light frequency to achieve state-independent trapping. Polarization configurations are adjusted to suppress vector shifts. This detailed approach, notably tracing lattice laser frequencies to the UTC NIST timescale via an optical frequency comb, ensures that both systematic errors and long-range dipolar interactions are minimized. The authors present data supporting their claim that systematic frequency shifts induced by both scalar AC Stark shifts and vector Stark effects are measurable with extreme precision.

The theoretical framework developed for handling these frequency shifts proves crucial in achieving measurement precision at the $5 \times 10^{-19}$ level within an hour of averaging time. Future developments hinted at by the authors include scaling strategies for reducing quantum projection noise (QPN) through increased atomic coherence and atom numbers, refining clock stability.

Extending their methodology offers potential in various scientific domains, from precise gravitational wave detection to exploring many-body quantum systems. With the groundwork of controlling interactions laid, subsequent research can explore phenomena such as collective frequency shifts and the broader implementation of dipolar quantum gases within optical lattice clocks.

In conclusion, transitioning to a 3D optical lattice with Fermi-degenerate gases marks a noteworthy step forward in optical clock technology. The intricate balance between interaction control and atomic density achieved in this paper lays a foundational framework for the next generation of precision measurement tools that will inform theoretical physics and practical applications in timekeeping, beyond the constraints of traditional atomic clock systems.