Is matter-antimatter annihilation similar at all to nuclear fusion?
It is similar in the sense that mass gets converted into photon energy, but otherwise they are pretty different processes. Matter-antimatter annihilation is an extremely efficient conversion: all of the mass gets turned into energy. This is probably why science fiction writers like to invent antimatter drives. In contrast, nuclear fusion is a process in which the fused nucleus has less mass than the separated constituents, and the mass difference is converted into photons; but there’s plenty of mass “ash” left over and the energy per fuel mass you get out is much smaller than for matter-antimatter annihilation.
