Quantum Immortality

[Chaos Creator]

First a little background:
Schrödinger's Cat: A cat, along with a flask containing a poison and a radioactive source, is placed in a sealed box shielded against environmentally induced quantum decoherence. If an internal Geiger counter detects radiation, the flask is shattered, releasing the poison that kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead. Yet, when we look in the box, we see the cat either alive or dead, not both alive and dead.

Quantum immortality is a metaphysical speculation derived from the quantum suicide thought experiment. It states that the many-worlds interpretation of quantum mechanics implies that conscious beings are immortal. Hugh Everett is reported to have believed in quantum immortality, although he never published on either quantum suicide or quantum immortality.

Unlike Schrödinger's cat-in-a-box thought experiment which used poison gas and a radioactive decay trigger, this human version involves some sort of lethal weapon and a machine which measures the spin value of a photon. Every 10 seconds, the spin value of a randomly passing photon is measured. Depending on the orientation of the spin, either the weapon is deployed and the man is killed, or it is not and he lives.

With each run of the experiment there is a 50-50 chance that the weapon will be triggered and the experimenter will die. According to the Copenhagen interpretation, the weapon will (in all likelihood) eventually be triggered and the experimenter will die. If the many-worlds interpretation is correct then at each run of the experiment, the experimenter will be split into several worlds in which he dies and a few worlds in which he survives. In the worlds where the experimenter dies, he will cease to be a conscious entity.

However, from the point of view of the non-dead copies of the experimenter, the experiment will continue running without his ceasing to exist, because at each branch, he will only be able to observe the result in the world in which he survives, and if many-worlds is correct, the surviving copies of the experimenter will notice that he never seems to die, therefore "proving" himself to be invulnerable to the killing mechanism in question, from his own point of view.

If the many-worlds interpretation is true, the measure (given in the many-worlds interpretation by the squared norm of the wavefunction) of the surviving copies of the experimenter will decrease by 50% with each run of the experiment, but will remain non-zero. So, if the surviving copies become experimenters, those copies will either die during their first attempt, or survive creating duplicates of themselves (copies of copies, that will survive finitely or die).

The idea behind quantum immortality is that, in running the quantum thought experiment, the experimenter may remain alive and, thus, able to experience at least one of the universes in this set (even though these universes form a tiny subset of all possible universes). Over time, the experimenter would therefore never perceive his or her own death.