  We report the observation and control of ultrafast non-equilibrium many-body
electron dynamics in Rydberg-excited spatially-ordered ultracold atoms created
from a three-dimensional unity-filling atomic Mott insulator. By implementing
time-domain Ramsey interferometry with attosecond precision in our Rydberg
atomic system, we observe picosecond-scale ultrafast many-body dynamics that is
essentially governed by the emergence and evolution of many-body correlations
between long-range interacting atoms in an optical lattice. We analyze our
observations with different theoretical approaches and find that quantum
fluctuations have to be included beyond semi-classical descriptions to describe
the observed dynamics. Our Rydberg lattice platform combined with an ultrafast
approach, which is robust against environmental noises, opens the door for
simulating strongly-correlated electron dynamics by long-range van der Waals
interaction and resonant dipole-dipole interaction to the charge-overlapping
regime in synthetic ultracold atomic crystals.
