Quantum suicide

[SinJin]

This is a question for those of you familiar with the quantum suicide thought experiment.

In the experiment, the person going through the suicide procedure would see themselves as always surviving. However, for some observer, i.e. a lab technician, it would appear that the odds are always the same and therefore wouldn't see any sign of the person always surviving.

This experiment arrises from the theory that the universe splits into different possible histories. If you have a gun hooked up to some atom that has a 50% probability of either decaying or not decaying, and it'll fire if the atom decays, and you aim it at yourself, then the universe will split into one possibility where the atom does decay and you are shot, and one possibility where it does not decay and you survive. Each time you run the experiment, that split occures, and you always find yourself in the universe where you survived and the gun didn't fire because you can't find yourself in the one where you were killed. That explains why it appears to you that you always survive. However, I would think that to an observer they would notice the same thing, that you always survive. Here's why I think this:

Say you have a lab tech watching the experiment. You run it, and the universe splits into A and B. In universe A you are shot and the tech sees you die, and the experiment is over. In B, however, the gun is not fired and you survive, and the tech notices this. The tech even writes it down on a notepad that the experiment was run once and you survived. Note that in universe A you died, and so the experiment wasn't continued and there were no branching paths from A. But you survived in B, and so you run the experiment again. Universe B splits off into universe C and D. In C, you are shot. The tech looks at his notepad and writes down that the experiment was run twice, that it took two runs for the gun to go off and kill you. However, in universe D, the gun did not go off. In universe D, you survived the first experiment where the universe split into A and B, and then you also survived when universe B split into C and D. In universe D you survived two runs of the experiment. The tech writes down in his notepad that the experiment was run twice and that you survived both times. Note again that in universe C you were shot and the experiment was stopped.

What am I getting at here? In universe B you and the tech saw yourself survive the experiment once, and then in universe D you both saw yourself survive it again. It was recorded on the tech's notepad even. So let's say you run the experiment 30 times. Each run of the experiment, there's a lab tech who marks down in his notepad that you died on that run. So there's a notepad that say you die on the 1st run, the 2nd run, the 3rd run, ect... all the way to 30, where you die on the last run. But there is also a notepad that shows you survived each run, including the 30th, the 31st, the 32nd, and so on. So, finally to my question... if someone was to actually carry out this experiment, on the 30th run wouldn't the lab tech agree that he's survived 30 times? Or on the 1 millionth run the lab tech would agree he's survived 1 million times? After all, he has the recorded runs of the experiment on paper.

Please, if anyone can help me out with this that would be great. I know this experiment is derived from the Schrodinger's cat experiment, which was originally only intended to prove the loop holes in some of quantum mechanic's interpretations. I'm just curious about the observer and there chances of seeing you survive indefinately. Thanks.

[Guille]

sinjin,

I don't know much QM math but I think I can answer your question.

As you said, each time the experiment is done there are two possibilities, so two universes or histories come out. At each of these possibilities, the observer that takes notes does survive, no matter what (this is if we ONLY count the experiment histories, of course, there is a history where the lab explodes, another one where he isn't in the lab, another one with the end of the universe.....etz). Imagen that you die in the first experiment, then, in this history, he will say that only 1 experiment was done. If you survive to the first but not to the second, in this history, he will say that there were 2 experiments. And so on.

So, if you survive to the thirty experiments, then, he will say that there were 30 experiments done and that you survived to all. He won't have knowledge of the failed experiment histories.

This is something I had questioned to me before. Because my solution only works iff and only iff the "creation" of each history is espontanous (timeless).

[SinJin]

That all makes sense, but I don't think it answers my question. Say I had the gun pointed at me, and you were the lab technician. After 30 runs of the experiment, I could turn toward you and say "see! I can't die!" and you would agree, because you've been there for all 30 runs.

I understand that in each run of the experiment, there would be an observer (lab tech) who sees you die. but the lab tech who sees you die would only be in the universe where you die and the expreiment is ended. The lab tech that you see is the one that's with you in the universe, and hence the one that sees you live each time.

So, back to my originally question, I don't see why you wouldn't be able to show an outside observer that you can survive each run.

[Guille]

I think I did answer.

You prove. But only to the lab tech of the history in which you survive. The fact that YOU don't live doesn't mean that he alsos tops existing. The lab tech who sees you fail at the second experiment will verify this and be definatelly sure that you died at this stage.

You do prove it to the lab tech if you survive. But again, the whole thing depends on what I previouslly stated in my last post: the new history is created in zero time. And, in a way, don't you think that all the histories already exist? you don't create them, the possibilities are there, so they exist.

[SinJin]

So for each run of the experiment, if we concentrate on just the two lab techs that exist for the two possibilities of the gun firing or not firing, then there will always be a lab tech who sees you die and concludes that the experiment is not fool proof, and another lab tech who always sees you survive and concludes that you can't die. You will always find yourself in the next universe where you survive, however the tech from this universe where you survive may find themselves in the next universe where you die. So for each tech in each universe, there is an equal chance that they will end up in the next universe where you either die or survive? is that where the equal chances arrises for the observer?

[Guille]

Yes and no.

Yes in the case that we assume that there is ONLY one thing that has several possibilities (the experiment). Here, because there is 50% you die and 50% you live, the observer has 50% being in universe with you alive and 505 being in universe with you dead.

No because the experiment would never be the only determining thing. Because there is also a possibility in which the whole lab explodes and both die. Now, the possibility would be 33.3% for each case (alive-alive, alive-ded, deadi-dead). But of course, this doens't stop here. There are infinite number of possible histories.

[AntonioLao]

this discussion about the suicide act at the quantum level implies the existence of one absolute path. If this path is the fate or destiny then the free will is the choice of taking an alternate path. But the hard fact is still that in QM, path is meaningless. But the classical path is just a sum over all histories over the Lagrangians (difference of energies) as in Feynman's diagrams of his path integrals. The path is always classical but can have no meaning at the quantum level.

[SinJin]

this discussion about the suicide act at the quantum level implies the existence of one absolute path. If this path is the fate or destiny then the free will is the choice of taking an alternate path. But the hard fact is still that in QM, path is meaningless. But the classical path is just a sum over all histories over the Lagrangians (difference of energies) as in Feynman's diagrams of his path integrals. The path is always classical but can have no meaning at the quantum level.

When I posted the question I did indeed keep in mind that this quantum suicide experiment could not actually be performed, hence the fact that it's a thought experiment. For the sake of science fiction though I was curious as to what would happen if all of it was actually possible.

[AntonioLao]

this quantum suicide experiment could not actually be performed

it can be done at the classical level but not at the quantum level. The experiment is deterministic instead of stochastic. That is to say, the experiment is a collapse of the wave function of QM and can be distinguish from the EPR experiment

http://www.lassp.cornell.edu/ardloui...e/Schrcat.html

[Guille]

it can be done at the classical level but not at the quantum level. The experiment is deterministic instead of stochastic. That is to say, the experiment is a collapse of the wave function of QM and can be distinguish from the EPR experiment

http://www.lassp.cornell.edu/ardloui...e/Schrcat.html

What do you mean by collapse of the wave function?