Editing Quantum suicide and immortality (section)

==Thought experiment==
The quantum suicide thought experiment involves a similar apparatus to [[Schrödinger's cat]] – a box which kills the occupant in a given time frame with probability one-half due to [[quantum uncertainty]].<ref group=note>The simplest example of this is a weapon triggered by a [[two level system]]. Schrödinger described his as a radioactive decay detector while Moravec's was a device measuring the [[Spin (physics)|spin value]] of protons.</ref> The only difference is to have the experimenter recording observations be the one inside the box. The significance of this thought experiment is that someone whose life or death depends on a [[qubit]] could possibly distinguish between [[interpretations of quantum mechanics]]. By definition, fixed observers cannot.<ref name=tegmark98/>

At the start of the first iteration, under both interpretations, the probability of surviving the experiment is 50%, as given by the squared norm of the [[wave function]]. At the start of the second iteration, assuming a single-world interpretation of quantum mechanics (like the widely-held [[Copenhagen interpretation]]) is true, the [[Wave function collapse|wave function has already collapsed]]; thus, if the experimenter is already dead, there is a 0% chance of survival for any further iterations. However, if the [[many-worlds interpretation]] is true, a superposition of the live experimenter ''necessarily'' exists (as also does the one who dies). Now, barring the possibility of [[afterlife|life after death]], after every iteration only one of the two experimenter superpositions – the live one – is capable of having any sort of conscious experience. Putting aside the philosophical problems associated with [[Identity (philosophy)|individual identity and its persistence]], under the many-worlds interpretation, the experimenter, or at least a version of them, continues to exist through all of their superpositions where the outcome of the experiment is that they live. In other words, a version of the experimenter survives all iterations of the experiment. Since the superpositions where a version of the experimenter lives occur by quantum necessity (under the many-worlds interpretation), it follows that their survival, after any realizable number of iterations, is physically necessary; hence, the notion of quantum ''immortality''.<ref name=tegmark98/>

A version of the experimenter surviving stands in stark contrast to the implications of the Copenhagen interpretation, according to which, although the survival outcome is possible in every iteration, its probability tends towards zero as the number of iterations increases. According to the many-worlds interpretation, the above scenario has the opposite property: the probability of a version of the experimenter living is necessarily one for any number of iterations.<ref name=tegmark98/>

In the book ''Our Mathematical Universe'', [[Max Tegmark]] lays out three criteria that, in abstract, a quantum suicide experiment must fulfill: 
* The random number generator must be quantum, not deterministic, so that the experimenter enters a state of superposition of being dead and alive.
* The experimenter must be rendered dead (or at least unconscious) on a time scale shorter than that on which they can become aware of the outcome of the quantum measurement.<ref group=note>This is not unanimously agreed upon. Sebens argues, as will be detailed ''infra'', that death must be instantaneous, not merely faster than the brain can process the result of the experiment.</ref>
* The experiment must be virtually certain to kill the experimenter, and not merely injure them.<ref name="Tegmark2014">{{cite book |last=Tegmark |first=Max |year=2014 |chapter=The Level III Multiverse/Is Time An Illusion?|title=Our Mathematical Universe |publisher=Vintage Books}}</ref>