If the many worlds (or many interacting worlds) theory of quantum mechanics is correct, then every time there is a decision point, a possibility of something going one way or the other, including our dying or not dying, the entire universe bifurcates into two, one in which the event goes one way and one in which it goes the other, including our dying or not, and we also bifurcate with it, one copy of us goes with one universe, the other with the other, and in the case of dying or not, one copy of us always lives on.

     So in some copy of the universe, there will be a copy of us, a version of us, that is immortal.