An antimatter weapon is a hypothetical device using antimatter as a power source, a propellant, or an explosive for a weapon. Antimatter weapons are not thought to currently exist due to the cost of production and the limited technology available to produce and contain antimatter in sufficient quantities for it to be a useful weapon. The United States Air Force, however, has been interested in military uses – including destructive applications – of antimatter since the Cold War, when it began funding antimatter-related physics research. The primary theoretical advantage of such a weapon is that antimatter and matter collisions convert and produce a greater fraction of the weapon's mass into explosive energy when compared to a hydrogen fusion reaction, which is only on the order of 0.4%. Th