Quantum torpedo
Quantum torpedoes (often abbreviated as QT in fandom) are guided missile weapons used by the Federation Starfleet. Introduced around 2371[1], they have yet to see widespread adoption in the fleet.
Description
Quantum torpedo casings have never been shown on-screen. After launch, QTs are visually similar to photon torpedoes, albeit brighter and glowing white/blue as opposed to photons' red/gold colour[2]. Quantum torpedoes are not compatible with standard photon torpedo launchers, but they can be made compatible through field modifications[3]. Two different QT launcher systems have so far been shown; the type mounted on the Defiant-class starship fires up to three torpedoes with ~0.5 second intervals[4], while the "turret" seen on the Sovereign-class launches a five-torpedo burst in rapid succession[5].
Usage
Little, if anything, is known of the quantum torpedo's operating principles or characteristics. They have not shown significantly greater yield, maneuverability or tracking ability compared to photon torpedoes; their scarcity suggests that their production is more difficult and/or resource-intensive than that of photon torpedoes. Despite this, Starfleet considers them to be tactically superior to photon torpedoes, deploying them only to new or recently-refitted vessels[6] and limiting their use in battle to when a hit can be guaranteed[7]. The Cardassian Union has successfully reverse-engineered quantum torpedoes, but has decided against fleet wide adoption[8].