High-Stability Single-Ion Clock with $5.5\times 10^{-19}$ Systematic Uncertainty

Mason C. Marshall, Daniel A. Rodriguez Castillo, Willa J. Arthur-Dworschack +10

We report a single-ion optical atomic clock with fractional frequency uncertainty of $5.5\times 10^{-19}$ and fractional frequency stability of $3.5 \times10^{-16}/\sqrt{τ/\mathrm{…