By a creative interpretation of the many worlds interpretation of quantum mechanics, all possible (in some sense) things happen (in some sense), though with varying probability measure (whatever this means). Additionally, since you must exist in order to perceive things, the probability of you observing things is in fact their conditional probability given that you exist (in some sense). If you die (in some sense), you no longer exist, so you can never experience yourself dying and are thus (subjectively) immortal (probably).

Proposals to abuse quantum immortality to gather easy-to-verify but hard-to-generate information (approximately, solutions to NP problems) are frequent: however, they are unworkable, even subjectively, since your decisions are also part of the world. These proposals would involve dying in the majority of timelines, so there is much less total probability mass where one lives conditional on deciding to do this, so on average you won't have observed yourself deciding to do this, so you won't.