A Fermi-degenerate three-dimensional optical lattice clock

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Science  06 Oct 2017:
Vol. 358, Issue 6359, pp. 90-94
DOI: 10.1126/science.aam5538

Making a denser optical lattice clock

Some of today's most advanced clocks are made up of large numbers of atoms lined up in a one-dimensional (1D) optical lattice. The numbers improve clock stability, but atomic interactions can limit accuracy. Campbell et al. loaded their fermionic strontium atoms into a 3D optical lattice. The low temperatures and strong interactions ensured that the atoms avoided one another, resulting in a neat pattern where each lattice site was occupied by exactly one atom. This ordering reduced the influence of interactions on the clock's accuracy, whereas the high density of atoms enabled by the 3D geometry improved the precision.

Science, this issue p. 90


Strontium optical lattice clocks have the potential to simultaneously interrogate millions of atoms with a high spectroscopic quality factor of 4 × 1017. Previously, atomic interactions have forced a compromise between clock stability, which benefits from a large number of atoms, and accuracy, which suffers from density-dependent frequency shifts. Here we demonstrate a scalable solution that takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional (3D) 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 measurement precision of 5 × 10–19 in 1 hour of averaging time.

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