Enhanced Differential Stability Measurements with a Multiplexed Strontium Optical Lattice Clock*

The extremely high precision of optical lattice clocks enable their use in novel tests of fundamental physics. Currently, one of the primary factors limiting optical lattice clock performance is the coherence of the clock laser, with only a handful of highly specialized clock lasers in the world operating with linewidths approaching the natural line width of ⁸⁷Sr’s clock transition (~1 mHz). In this talk, we will present our implementation of a multiplexed Sr optical lattice clock that overcomes the limitations imposed by clock laser coherence by utilizing synchronous differential measurements between multiple ensembles of ultra-cold, neutral ⁸⁷Sr atoms held in spatially separated regions of an optical lattice. We report atom-atom Ramsey coherence times exceeding 10 seconds with a ~1 Hz linewidth clock laser, and differential stabilities below 3×10−17/√τ obtained by synchronous Ramsey interrogation of two ensembles. Lastly, we will discuss on-going and planned applications of the multiplexed optical lattice clock to tests of relativity, including measurements of the gravitational redshift at the sub-cm scale and studies of the special relativistic effects of accelerations on clocks.