  Quantum tunneling constitutes one of the most fundamental processes in
nature. We observe resonantly-enhanced long-range quantum tunneling in
one-dimensional Mott-insulating Hubbard chains that are suddenly quenched into
a tilted configuration. Higher-order many-body tunneling processes occur over
up to five lattice sites when the tilt per site is tuned to integer fractions
of the Mott gap. Starting from a one-atom-per-site Mott state the response of
the many-body quantum system is observed as resonances in the number of doubly
occupied sites and in the emerging coherence in momentum space. Second- and
third-order tunneling shows up in the transient response after the tilt, from
which we extract the characteristic scaling in accordance with perturbation
theory and numerical simulations.
