An antimatter weapon is a hypothetical device using antimatter as a power source, a propellant, or an explosive for a weapon. Antimatter weapons do not currently exist due to the cost of production and the limited technology available to produce enough antimatter in sufficient quantities for it to be an acceptable 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, though significantly limited by neutrino losses, still convert a larger fraction of the weapon's mass into explosive energy than a fusion reaction in a hydrogen bomb, which is on the order of only 0.7%.
On March 24, 2004, Eglin Air Force Base Munitions Directorate official Kenneth Edwards spoke at the NASA Institute for Advanced Concepts. During the speech, Edwards ostensibly emphasized a potential property of positron weaponry, a type of antimatter weaponry: Unlike thermonuclear weaponry, positron weaponry would leave behind "no nuclear residue", such as the nuclear fallout generated by the nuclear fission reactions which power nuclear weapons. According to an article in San Francisco Chronicle, Edwards has granted funding specifically for positron weapons technology development, focusing research on ways to store positrons for long periods of time, a significant technical and scientific difficulty.
There is considerable skepticism within the physics community about the viability of antimatter weapons. According to an article on the website of the CERN laboratories, which produces antimatter on a regular basis, "There is no possibility to make antimatter bombs for the same reason you cannot use it to store energy: we can't accumulate enough of it at high enough density. (...) If we could assemble all the antimatter we've ever made at CERN and annihilate it with matter, we would have enough energy to light a single electric light bulb for a few minutes.