  HD 100546 is a well-studied Herbig Be star-disk system that likely hosts a
close-in companion with compelling observational evidence for an embedded
protoplanet at 68 AU. We present ALMA observations of the HD 100546 disk which
resolve the gas and dust structure at (sub)mm wavelengths. The CO emission (at
345.795 GHz) originates from an extensive molecular disk (390+/-20 AU in
radius) whereas the continuum emission is more compact (230+/-20 AU in radius)
suggesting radial drift of the mm-sized grains. The CO emission is similar in
extent to scattered light images indicating well-mixed gas and um-sized grains
in the disk atmosphere. Assuming azimuthal symmetry, a single-component
power-law model cannot reproduce the continuum visibilities. The visibilities
and images are better reproduced by a double-component model: a compact ring
with a width of 21 AU centered at 26 AU and an outer ring with a width of
75+/-3 AU centered at 190+/-3 AU. The influence of a companion and protoplanet
on the dust evolution is investigated. The companion at 10 AU facilitates the
accumulation of mm-sized grains within a compact ring, ~ 20 - 30 AU, by ~ 10
Myr. The injection of a protoplanet at 1 Myr hastens the ring formation (~ 1.2
Myr) and also triggers the development of an outer ring (~ 100 - 200 AU). These
observations provide additional evidence for the presence of a close-in
companion and hint at dynamical clearing by a protoplanet in the outer disk.
