A Wannier-Stark Optical Lattice Clock With Extended Coherence Times


The pursuit of ever improving accuracy and precision in atomic clocks is inextricably linked to discovery. With each new decade we gain deeper insight into nature, probing ever smaller energy scales. In this thesis we report a body of research advancing our 1D strontium optical lattice clock (Sr1) to the frontiers of accuracy, precision, and atomic coherence. We demonstrate a new record for strontium clock fractional frequency inaccuracy of 2.0×10−18. We then leverage this in a series of comparisons, first comparing Sr1 with the Al+ and Yb clocks at NIST to 18 digits of accuracy. Intra-lab comparisons with the 3D Sr lattice clock demonstrate record low instability between two independent clocks (3.5 × 10−17 at 1 s). High uptime characterization and steering of Si3 by the Sr1 system further demonstrates a proof of principle all-optical timescale system.

To move into the unknown, we introduce the newest version of Sr1. Utilizing a large waist, invacuum build up cavity we radically increase the homogeneity within the clock system. Operation at shallow trap depths allows us to realize a Wannier-Stark optical lattice clock. By tuning the delocalization of atomic wavefunctions we demonstrate the so called ‘magic depth’, where the clock frequency is free of atomic interaction induced frequency shifts regardless of atom number. Combining these advances in precision we demonstrate a fractional frequency uncertainty of 4.4 × 10−18 at 1 s of operation and 8 × 10−21 after 90 hours of operation, demonstrating nearly a factor of 100 lower uncertainty than the previous record. These advances allow us to rapidly evaluate gradients across our millimeter length atomic sample, resolving the gravitational redshift within a single clock.

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Department of Physics
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University of Colorado Boulder
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