The only way you really can make antimatter is by pair production – i,e, you create a particle and its antiparticle simultaneously. To be able to do this, you need, as a minimum, to supply energy equivalent to the mass of the created particle pair, which incidentally is the same energy that is freed when you annihilate it again (i.e. fire your antimatter bomb), hence the claims that in order to release the energy needed to destroy a city, you first need to invest the energy needed to destroy a city.
What quarks make up an anti-proton? If it were possible to rearrange quarks, could you produce it from ordinary matter? If so, I think that would be the “unknown method”. Just like the method of converting lead to gold would be to add 3 protons (and 7 neutrons to make it stable). Not that either is currently doable, but, at least, conceivable.
I’m not sure that antimatter bombs would be all that hard to detect. Even in the hardest vacuum we could produce, there’d still be a few random molecules that would probably be triggering constant matter-antimatter events. And even if you had a complete vacuum, there’re still cosmic rays and other background radiation that would be penetrating your containment.
I don’t know how much energy would be produced, but I’m guessing that your golf ball of antimatter would show up quite well on most radiation detectors.
Anti-quarks. 
And as for manipulating quarks, there you have the problem that they don’t really exist on their own – the strong force exhibits something called colour confinement, which basically means that if you try to separate quarks from each other, all you’ll succeed in doing is creating new quark-antiquark pairs bound to the quarks you’re trying to separate, and thus, new hadrons. I phrased that poorly – try to break apart a hadron into its constituent quarks, and all you’ll end up with are more hadrons.
Once. In 1982. For considerably less than twenty minutes.
Valentines Day to be specific.
Specifically, two anti-up quarks and an anti-down quark.
An anti-up quark is usually the dealer in subatomic particles’ Friday night poker games. 
It is the reason you suspected. Have you any idea how much energy it would take to create “a couple of grams” of anti-anything? Clue: lots and lots. Making anti-matter is a very inefficient process, as the CERN links will tell you.
Have you read Robert Gilmore’s Alice in Quantumland? If you like quark puns, you’d like that book.
I’m sure that by the time we have to start worrying about anti-matter bombs, we’ll have force-fields to protect us.
I would think that in that future of yours, we’ll have built something to detect your golf ball-side anti-matter bomb as well. :rolleyes:
Even with today technology, your anti-matter bomb would be easily detected, radioactivity or not: try carrying the supporting hardware through the metal detector. I would even suspect that the anti-matter itself will show up funny on current detectors as well, what with the reversed polarity that will deflect the X-ray in different way etc…
Anan 7 assures me that they are a credible threat.
Don’t underestimate the power of a laptop. One was enough to destroy an entire invasion fleet.
Anyway, if you’ve got the tech to make antimatter, you can make H-Bombs much more easily.
Speaking of H-bombs, we can pretty much make an H-bomb with a yield as high as we’d like. The only reason we don’t is that the destruction of an H-bomb is already limited more by the distance to the horizon than by the size of the bomb. Anything above 10 megatons or so serves no purpose except for dick-waving contests between superpowers.
Obligatory link to largest bomb (yet):
Not practical for a variety of reasons, including that there’s only a couple of targets (major metropolitan areas) so large that you need something that powerful to destroy them.
50MT is 2.1x10^17J which if my math is right represents the total conversion of about 2.3kg into energy.
Don’t you just drop this statement in conversation without some sort of link, you vixen!
I’m surprised the event itself doesn’t have a Wikipedia page, but here’s the discoverer. Nobody’s quite sure what to make of this event: It looked pretty much exactly like a real monopole should, but nobody’s ever seen another one, despite running far more extensive searches than this one. Maybe it was a real monopole, and Dr. Cabrera just happened to be lucky enough to see one (or everyone else was just unlucky enough not to). Maybe it was a glitch of some sort in the equipment that just happened to look exactly like a monopole. Maybe the nature of the glitch was such that it would for some reason be expected to look exactly like a monopole without being one. Maybe it was a deliberate hoax. With only one event, it’s really impossible to say.
Re. storage: I have no idea what storing anti-lithium “in solution” means, but I have heard it proposed that anti-protons could conceivably be confined as negative ions within a suitable crystal lattice.
Incidentally, forget about anti-matter bombs being radiologically “clean”: even a simple proton-antiproton reaction produces lots of intermediate products, and an anti-proton (or anti-neutron) colliding with a nucleus of ordinary matter would blast it into lots of unstable fragments.
Couldn’t you just create a lot of anti-matter at the same time you created a lot of matter, for a net energy cost of zero? Disclaimer: I have no idea what I’m talking about.