I finally managed to put together the latest theoretical know-how concerning antimatter based high yield energy production. Without further due... check out Antimatter Bomb. The paper lays out the theoretical blueprint for antimatter based bomb, it presents needed core material (solid hydrogen), theoretical requirements and used method. The paper does not describe any technical requirements, engineering solutions and so on. Pulling off a technical solution take (most likely) several years, hence sooner we start the research then bigger are the chances for preventing surprise asteroids.
I regard my paper as informative as saying that by splitting Uranium-235 atoms with neutrons we can release energy, it's just theoretical knowledge. Of course antimatter based energy production as described in the paper is easier to accomplish than e.g. fission based energy production, but never the less, it's just theoretical knowledge, and on top of that, it's highly speculative paper!
I do hope that my paper generates some debate and possibly encourages some bold experimental particle physicists to give it a try. Let's hope for the best!