A Wannier-Stark Optical Lattice Clock with Extended Coherence Times

Ever improving precision and accuracy in atomic clocks are inextricably linked to discovery, with each new decade exploring smaller energy scales. Here we report on the operation of a state-of-the-art 1D strontium optical lattice clock. We demonstrate a record low Sr clock inaccuracy of 2.0×10-18. Frequency comparisons with the Al+ and Yb clocks at NIST reach 18 digits of accuracy. Intra-lab comparisons with a 3D Sr lattice clock reveal a record fractional frequency instability between independent clocks of 3.5×10-17 at 1s. Motivated by these advances, we introduce and demonstrate a new lattice clock platform. A large waist, in-vacuum build-up cavity ensures homogeneity of the optical lattice while minimizing

atomic interactions. Shallow trap depths enable extended Wannier-Stark states. By tuning the delocalization of atomic wavefunctions we engineer our atomic clock to be free of atomic interaction induced frequency shifts - the so-called magic depth. Combining these advances, we demonstrate record measurement uncertainties of 4.4 × 10-18 at 1s and 8 × 10-21 at 90 hours. These advances allow us to rapidly evaluate field gradients across our millimeter length atomic sample, resolving to sub-millimeter the gravitational redshift within a single atomic ensemble.

*Work done at JILA/University of Colorado under the supervision of Professor Jun Ye