Atomic Coherence of 2 Minutes and Instability of 1.5 x 10^-18 at 1 s in a Wannier-Stark Lattice Clock

We explore the limits of atomic coherence and measurement precision in a 87Sr optical lattice clock. We
perform a detailed characterization of key effects, including lattice Raman scattering and atomic collisions
in a shallow lattice configuration, determining a 174(28) s 3P0 clock state lifetime. Investigation of atomic
coherence across a range of lattice depths and atomic densities reveals decoherence mechanisms related to
photon scattering and atomic interaction. At a reduced density, we observe a coherence time of 118(9) s,