Clock with 8 × 10^{−19} Systematic Uncertainty

We report an optical lattice clock with a total systematic uncertainty of 8.1 × 10⁻¹⁹ in fractional frequency units, representing the lowest uncertainty of any clock to date. The clock relies on interrogating the ultranarrow ¹S₀ → ³P₀ transition in a dilute ensemble of fermionic strontium atoms trapped in a vertically-oriented, shallow, one-dimensional optical lattice.