qCraft is not a simulation of quantum physics, but it does provide 'analogies' that attempt to show how quantum behaviors are different from everyday experience, allowing players to create structures and devices that exhibit Minecraft versions of quantum properties like observer dependence, superposition and entanglement.
This wiki provides documentation of the features and capabilities of the mod. For a thorough tour of what the mod can do, check out this overview from Direwolf20. You may also want to check out the qCrafting series of videos on the mod's official YouTube Channel.
ComputerCraft is a mod created for Minecraft by dan200 that adds Computers, Monitors, Modems, Turtles and more! ComputerCraft's Computers and Turtles are programmed with the easy-to-learn Lua programming language. You can use Redstone, RedPower or even MineFactory Reloaded alongside with your devices for the best experience.
This video (clocking in at 1 hr. 41 mins) provides details about how to use the Custom NPC mod and navigate and utilize the tools associated with the different tabs.