The Quantum Mechanics were DC comics supervillains.
Born at the Big Bang, the Quantum Mechanics roamed the universe, seeking celestial enlightenment. Fear of their own mortality, coupled with their inability to conceive of an afterlife, prompted Quantum Mechanics to create a vision of heaven. They created thousands of agents to study the cultures of the universe, gathering information about each version of heaven to build a perfect hereafter for themselves.
The JLA first discovered the Quantum Mechanics when these ancient beings abducted planet Earth as well as hundreds of other worlds they had been studying, to create their own ladder to heaven. When a rogue faction of the Quantum Mechanics threatened to destroy all these worlds, the JLA were forced to battle the cosmic creatures, eventually helping them to cross over into a higher plane of existence.