How is it possible to convince the other that they're right? Just stop.
Einstein, the world's greatest scientific mind, was not an Atheist. In fact, Copernicus was a devout Catholic, but he was upset that the Church disapproved of his work.
Well convicing someone to stop believing in a delusional fantasy is hard, they believe it to be true, they demand evidence to stop believing, where no evidence can be found because of the nature of the delusion.
Logic is the only cure, however, logical thinking is not something that can be forced onto someone suffering from delusion, it can be explained but it won't necessarily be absorbed.
Logical thought is mostly aquired by a person on thier own, which is a step to leaving the god delusion.
Einstein was born into his religion, as have most human beings that existed, even with logical thought, you won't necessarily stop believeing in God, however this is easier today because of scientific breakthroughs that Einstein himself helped to forge, .we now have alternate answers to creation, God is no longer the logical answer. Einstein theorised that the universe had a begging however he never could deduce how it happend, thus the only logical answer available to him, who created the big bang, well that would be god. It takes quantum mechanics and some other theories to try and theorise on it, but yet we still don't know everything (The Theory of Everything is still needed), however we know when the Universe was created and thus the time slot said god would have made it if indeed he/she/it did. Which is something I suppose in the path to prooving the god theory incorrect.
I mean its like this, If you were told as a child that Father Christmas is real which I'm sure you were, if no one ever told you it was not true, and even if someone did, Father Christmas had created "The Christmas Brouchure" and in it it stated that anyone saying he didnt exist was going to never get presents again and burn in eternal hell fire and was obviously lying then you would have no reason to believe them, but say for simplicity sakes, no one ever told you he didnt exist infact everyone agrees that he does, would you still believe in Father Christmas? Yes you would, You tend to believe in the things taught to you, the only way to change this is to either question everything or be taught something else.