when defining atheism. First of all atheism is a condition not a belief. You can't believe in not believing something. It's simply the condition of not believing in a deity, a-theism, no capitol "A" no article, I'm atheist not an Atheist.
As for me there's simply no data for the existance of a deity. No more, no less, like no santa and no unicorns. If evidence presents itself I'd be more than happy to be first in line to change my position. Same with scientific evidence or observation based theory.
As for quantum physics you may want to brush up a little on that subject. There's a lot of observational data and it has been increasing rapidly. Do I believe in quantum physics? No. It's not a being or a thing so there's nothing to believe in. It's a system based on physics and observation. Systems prove or disprove themselves and they evolve as we observe and verify.
But there's not one single blip on the god issue. So a god would take faith. Faith is believing something that has no evidence. If there was evidence there wouldn't be faith, it would disapear the moment there was evidence. I have no faith in quantum physics because there's plenty of good math and observational evidence. I trust the evidence and the observations for now. Trust can change, faith cannot.
So I guess it's a little less simple than I thought.