If we are unaware of the vast majority of decisions that we're making (because they are made at a quantum level), how can we define the concept of good and evil? (saying that we made a good / bad decision requires from us being aware of it)
Decisions are not made at a quantum level. Human brains are classical, not quantum, computers. Quantum computers require very precise control over the components, whereas human brains are hot and wet.
Human decisions are things you can control and could be aware of. People aren't always aware of their decisions and motivations, but they could be more aware with better introspection, it's not just out of their hands.
A spider knows nothing of good or evil, all it knows is that it's hungry and how to sustain itself(survive). It bears no consideration for the other spider that might die because it gets the fly that the other doesn't
Humans know about giving and selfishness. A human, who has food, who is with another human, who's hungry, is evil/selfish if it eats all of the food, even though it's not hungry, and gives none to the other who is. A human that's hungry and eats the food is bowing to it's nature(survival) in not sharing with another hungry human. A hungry human that shares unfulfillingly or considerately with another hungry human is good, even though both will die.
Good and evil are concepts of individual perception, their nature, in as much as one is right/good and one is wrong/evil is only applicable when someone outside of the concepts deems it to be so, as such occurrences which happen without conscious awareness simply are outside of either of those categories. It's not really all that different from asking when a spider catches a fly if it's evil for doing so, if neither has a conceptual understanding of good or evil then those labels fail to have any meaning.