Multi-ensemble Strontium Optical Lattice Clock

Differential optical clock comparisons based on synchronous interrogation of multiple 87Sr clock ensembles have demonstrated unprecedented stability and atom–atom coherence times, enabling precision measurements of the gravitational redshift on the millimeter scale [1,3]. Here, we present recent experimental results studying the limitations to differential clock coherence times and demonstrating enhanced coherence using an erasure-conversion technique adapted from neutral atom quantum computing architectures [2]. By mapping dominant decoherence channels onto detectable erasure events, we demonstrate a two-fold enhancement of the atom-atom coherence time in a differential optical lattice clock comparison. This approach enables extended interrogation times and a reduction in clock instability without additional technical complexity. We further outline the design and prospects of a second-generation, multi-ensemble strontium clock platform aimed at precision measurements of gravitational redshift over meter-scale baselines. By operating spatially separated clock ensembles with correlated interrogation and adaptive protocols, this system targets substantially improved sensitivity to relativistic time dilation and provides a realistic pathway toward fundamental tests of gravity in the lab.

 

[1] X. Zheng, J. Dolde, V. Lochab, B. N. Merriman, H. Li, and S. Kolkowitz, Differential clock comparisons with a multiplexed optical lattice clock, Nature 602, 425 (2022).

[2] S. Ma, J. Dolde, X. Zheng, D. Ganapathy, A. Shtov, J. Chen, A. Stoeltzel, and S. Kolkowitz, Enhancing optical lattice clock coherence times with erasure conversion, PRX Quantum 9, 040340 (2025)

[3] T. Bothwell, C. J. Kennedy, A. Aeppli, D. Kedar, J. M. Robinson, E. Oelker, A. Staron, and J. Ye, Resolving the gravitational redshift across a millimetre-scale atomic sample. Nature 602, 420–424 (2022).