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. Quantum torpedoes are not compatible with standard photon torpedo launchers, but they can be made compatible through field modifications. 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, while the "turret" seen on the Sovereign-class launches a five-torpedo burst in rapid succession.
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 and limiting their use in battle to when a hit can be guaranteed. The Cardassian Union has successfully reverse-engineered quantum torpedoes, but has decided against fleet wide adoption.