It seems that quantum torpedeos are the next generation of photon torpedoes but I was wondering what made them better and what makes them 'quantum'.
Quantum torpedoes used a plasma warhead while photon torpedoes used a matter/antimatter warhead.
From what I understand about matter and antimatter, I would think that a photon torpedo is much more powerful, unless the plasma used in a quantum torpedo somehow produces a more powerful explosion...
But, this is where inconsistencies in quasi-science come from, lol.
The two main differences between a "Quantum" torpedo and a "Photon" torpedo are the yield from the explosive warhead and the mechanism by which the explosion itself occurs.
According to the DS9 Technical Manual, the explosive force from a Photon torpedo is 18.5 isotons (a fictional measure that doesn't translate directly into megatonnes) with a theoretical upper limit of 25 isotonnes given ideal conditions.
This compares with the maximum potential yield from a Quantum torpedo of around 52.3 isotons, substantially more than double.
Memory Alpha notes that this conflicts on a couple of occasion with TV and film canon statements about photon torpedoes with yields into the hundreds of isotons but we can generally ascribe these to production errors.
To quote the TNG Technical Manual, a Photon torpedo works by using...
...Variable amounts of matter and antimatter [ which are ] both held in suspension by powerful magnetic field sustainerswithin the casing at the time of torpedo warhead loading. They are held in two separate regions of the casing, however, until just after torpedo launch, as a safety measure.
The suspended component packets are mixed, though they still do not come into direct contact with one another because of the fields surrounding each packet. At a signal from the onboard detonation circuitry, the fields collapse and drive the materials together, resulting in the characteristic release of energy.
By comparison, a Quantum torpedo uses the energy from a standard matter/antimatter explosion to generate a 'vacuum membrane'. This vacuum draws in particles from alternate dimensions and the resulting influx of particles creates a huge amount of extra energy.
The basic mechanism...involved the formation of an eleven-dimensional space-time membrane. A cousin of the superstring, the membrane was twisted into a string with a topology of Genus 1 and pinched off from the background vacuum, calling into existence a new particle. The process of creating large numbers of new subatomic particles liberated correspondingly large amounts of energy. Calculations quickly showed that a relatively small volume of ultraclean vacuum carried aboard a torpedo warhead could place a highly explosive energy release on the target.
The zero-point initiator is powered by the detonation of an uprated photon torpedo warhead with a yield of 21.8 isotons, achieved through increased matter-antimatter surface area contact and introduction of fluoronetic vapor. The M/A reaction occurs at four times the rate of a standard warhead. The detonation energy is channeled through the initiator within 10^ -7 seconds and energizes the emitter, which imparts a tension force upon the vacuum domain. As the vacuum membrane expands, over a period of 0,0001 seconds, an energy potential equivalent to at least fifty isotons is created. This energy is held by the chamber for 10^ -8 seconds and is then released by the controlled failure of the chamber wall.
In terms of storytelling, they're the 'new, more powerful, superweapon' for DS9. Science! marches on, after all, even in Star Trek.
The Photon Torpedo is a technology dating back over a century (it was used in TOS) and has had only incremental improvements. Quantum Torps are an innovative new design which is markedly different from Photon Torps...in ways that are never fully explained.
Functionally, they seem to have better penetration of enemy shields, a higher explosive potential, and slightly greater tactical flexibility.
They were supplanted by 'transphasic torpedoes' in Voyager, which were capable of penetrating 'quantum shields' - evidently a defense against the improved penetration of q-torps.
That definition is from the game "Birth of the Federation". In the game they say that "Quantum Torpedo" is a euphemism for "Quantum mechanical shaping of a blast". As you said, it ensures that all of the torpedoes explosive force is directed at the target or its shields. Basically it's a fancy term for a shaped blast
I havn't got a source for this, its a vague memory from possibly one of the games, so bear with me :
When a photon torpedo detonates, the blast occurs in every direction. Much of the concussive force is wasted by not actually hitting your target.
When a quantum torpedo detonates, the blast is focused entirely towards the enemy, allowing for far greater destructive potential from the same explosive yield