How do you build a quantum suicide machine?

[Elias]

Hey!

I posted this thread hoping that there are experts about quantum physics here. Please if you do not know a lot about the subject, don't answer this question:

First things first, to be clear: I’m NOT building a quantum suicide machine and I’m NOT trying to kill myself. I’m just curious about multiverse theory and quantum physics and want to know how to build one.

If I’m not mistaken, the requirements are a subject, a kill mechanism, and a particle accelerator. But what exactly is a particle accelerator in this case and how do you build one? I know that the kill mechanism could be like a gun attached to the machine.

I find the idea about quantum suicide and the multiverse theory very fascinating, the reason I ask this question is simply because I'm curious.

Thanks!

 

[Nugatory]

Could you provide some references to what you've been reading and what you mean by "the multiverse theory"? There's a pretty good chance that you have been misled by non-serious popular treatments of quantum mechanics.

 

[mfb]

There is no need to build a machine. If many worlds is correct (whatever "correct" means), then there are worlds where you are dead, worlds where you were never born, and worlds where you will live forever.

 

[rootone]

You can't actually build one unless you a capable of engineering subatomic scale machines.
It's a thought experiment, a variation on the famous Schrödinger's cat.
The conclusion is that the experimenter has to survive, because if they don't there will no worlds at all. let alone multiple ones.
https://en.wikipedia.org/wiki/Quantum_suicide_and_immortality

 

[DrClaude]

If I build a quantum suicide machine and continuously monitor my state, I would be immortal through the quantum Zeno effect, even if Copenhagen is right!

 

[Nugatory]

If I build a quantum suicide machine and continuously monitor my state, I would be immortal through the quantum Zeno effect, even if Copenhagen is right!

You try it. I'll watch.
(But please, first make me the beneficiary of your life insurance policy).

 

[Flatland]

There is no multiverse theory. Just the MWI of QM.

 

[LeandroMdO]

Many worlds interpretations do not imply quantum immortality. That is a myth.

MWIs in general suffer from a serious problem: there is no precise, generally accepted definition of what a MWI *is*. As such, many of the common statements regarding its parsimony and elegance refer to some intuitive idea of what properties one such formulation would have. The trouble with intuition is that different things are intuitive for different people, and often times concepts that were legitimate in other interpretations of quantum mechanics find their way into discussions of MWIs as if they were legitimate there also.

The case of quantum immortality is even worse: it's the illegitimate borrowing of a concept that was never legitimate or precisely defined, namely, the relationship between wavefunction collapse and consciousness. These intuitions take consciousness as a primitive "thing" that splits as the worlds split. Your subjective experience then follows one of your "descendants" in Hilbert space, and as long as there is at least one you will never experience death. However, this metaphysical hypothesis about consciousness has no justification, and the fact that we "lose consciousness" all the time (typically once a day) means that Hilbert space doesn't care whether the computations happening in your brain are conscious or not. It's probably much more natural to regard consciousness as an emergent phenomenon that arises on timescales much longer than the typical decoherence time that leads to world-splitting, rather than a primitive substance that tracks states in Hilbert space. After the trigger on your quantum Russian roulette machine is pulled you might find "yourself" in a world where you are dead or one where you're alive, just as in ordinary Russian roulette.

 

[mfb]

There is no need to include consciousness in the discussion. You can also discuss the survival probability of a molecule, of a rock, or whatever, without changing the conclusion that it will break in many but not all worlds in MWI. The question "is that a desirable outcome?" is independent of that.

 

[LeandroMdO]

That is correct. It is the unnecessary and illegitimate insertion of consciousness in the discussion, likely borrowed from Wigner-esque views of quantum mechanics, that leads to the fallacious conclusion of quantum immortality.

 

[mfb]

That's not what I said.

You can discuss quantum immortality without considering consciousness or living objects at all.

 

[LeandroMdO]

Quantum immortality is not just the trivial statement that some of your descendants survive, according to some omniscient meta-observer that, unlike the rest of us mortals, has access to all branches of the wavefunction. Quantum immortality is the belief that if you play quantum Russian roulette, you will never experience death. The entire thought experiment is framed from a subjective point of view.

Otherwise, there is no distinction between many-worlds interpretations and other interpretations. All that a real observer can say, one that plays by the rules, is that you live or die with some probability, or that a molecule or a rock is intact or destroyed with some probability. That is true even if you play regular Russian roulette and your survival is conditioned solely on classical probabilities. Many worlds adds nothing.

 

[mfb]

Quantum immortality is the belief that if you play quantum Russian roulette, you will never experience death.

For suitable definitions of "experience death", it is true but also trivial - and true in all interpretations of quantum mechanics. The difference in MWI: "You" will survive for sure in some worlds.

 

[LeandroMdO]

For suitable definitions of "experience death", it is true but also trivial - and true in all interpretations of quantum mechanics.

Exactly.

The difference in MWI: "You" will survive for sure in some worlds.

The only difference is to some omniscient Laplace demon who knows the entire wavefunction. From "your" point of view (really from the point of view of any observer), there is no difference. It's just not a useful thought experiment. It's not about physics.

The original idea was that you could use quantum suicide to convince yourself, but not anybody else, that the MWI is correct. What I wish to emphasize is that you can't even convince yourself.

 

[durant35]

There is no need to build a machine. If many worlds is correct (whatever "correct" means), then there are worlds where you are dead, worlds where you were never born, and worlds where you will live forever.

How can the part about the worlds where you will live forever be true? If the universe ends in the heat death the probability for that will be 0.

 

[mfb]

There is always a "non-zero probability" (there is always a world in MWI) that something somehow resembling you stays together.

 

[durant35]

There is always a "non-zero probability" (there is always a world in MWI) that something somehow resembling you stays together.

How about an expanding universe driven by a cosmological constant which eventually empties out and leaves nothing behind? Surely no MWI forces and fluctuations/thermodynamical miracles can beat out the cosmological constant in the long run?

By the way, so you really believe that you will transcend death and experience immortality?

Please don't answer me with "one copy of me will and one won't" because that would be ignorant of my question. Do you believe that you can never end up in a branch where death is experienced and quantum immortality is viable?

 

[mfb]

By the way, so you really believe that you will transcend death and experience immortality?

No, I think it is pointless to spend much time wondering about those worlds with negligible amplitudes.
Yes, they exist, with and without cosmological constant, but I don't care about them, in the same way as I don't care about events with 10^10-10 probability in probabilistic interpretations.

Do you believe that you can never end up in a branch where death is experienced and quantum immortality is viable?

The question is ill-defined.

 

[durant35]

No, I think it is pointless to spend much time wondering about those worlds with negligible amplitudes.
Yes, they exist, with and without cosmological constant, but I don't care about them, in the same way as I don't care about events with 10^10-10 probability in probabilistic interpretations.

But how do they exist with the cosmological constant? If the universe empties out there will be nothing that can fluctuate and guarantee immortality.

The second question is not ill-defined, do you believe that you will die? Straightforward, a normal question. Saying that you don't care about low amplitude doesn't answer anything.

 

[Nugatory]

But how do they exist with the cosmological constant? If the universe empties out there will be nothing that can fluctuate and guarantee immortality.

The amplitudes decline asymptotically towards zero, but they never get to zero so there always remains some tiny but non-zero probability.

The second question is not ill-defined, do you believe that you will die? Straightforward, a normal question. Saying that you don't care about low amplitude doesn't answer anything.

That is a straightforward normal question that is pretty much unrelated to anything else we're discussing in this thread. Even classical thermodynamics admits of low probability outcomes in which things never die (assuming, for the sake of argument, that life is a mechanistic phenomenon completely described by physical laws).

 

[mfb]

But how do they exist with the cosmological constant? If the universe empties out there will be nothing that can fluctuate and guarantee immortality.

"The universe empties out" is not a fundamental law of nature. Objects not bound gravitationally or otherwise move away from each other. So what? That doesn't have a direct effect on a human, which is bound by electromagnetic forces.

The second question is not ill-defined, do you believe that you will die?

I will die in all worlds I care about.

 

[durant35]

"The universe empties out" is not a fundamental law of nature. Objects not bound gravitationally or otherwise move away from each other. So what? That doesn't have a direct effect on a human, which is bound by electromagnetic force

But eventually human bodies and structures disintegrate, right? We have atoms then black holes etc. I don't see how particles can conspirate to fluctuate every time since it gets harder and harder for them to interact due to expansion. The rate should be zero at one time.

Sean Carroll says that fluctuations exponentially fall off and that there are no fluctuations in de Sitter.
https://arxiv.org/abs/1505.02780

IQUOTE="mfb, post: 5723947, member: 405866"] will die in all worlds I care about.[/QUOTE]

That's more reasonable, thanks

 

[mfb]

But eventually human bodies and structures disintegrate, right?

Not with exactly 100% probability / not in every world.

I don't see how particles can conspirate to fluctuate every time since it gets harder and harder for them to interact due to expansion.

Every possible fluctuation happens in some world. It does not matter how "hard" it is.

Sean Carroll says that fluctuations exponentially fall off and that there are no fluctuations in de Sitter.

A Boltzmann brain comes out of nothing. That is not the starting point we discuss here.
But he doesn't even say that there are no fluctuations. He argues that there are no fluctuations in an infinite-dimensional Hilbert space.

 

[durant35]

Not with exactly 100% probability / not in every world.Every possible fluctuation happens in some world. It does not matter how "hard" it is.

If there's a suppression of fluctuations to 0 (like in Carroll's paper) it gets from hard to impossible.

A Boltzmann brain comes out of nothing. That is not the starting point we discuss here.

A BB is still a fluctuation like a person who survives indefinitely. And if fluctuations are suppresed that applies both to vacuum fluctuations and extremely improbable survivals due to rapid expansion of space.

But he doesn't even say that there are no fluctuations. He argues that there are no fluctuations in an infinite-dimensional Hilbert space.

Yeah, that's why the paper is titled "there are no fluctuations in de Sitter". I know that he mentions infinite hilbert space but that's the point of the paper, to show that there is a natural way to get rid of something that makes the theory wrong.

Anyway, nothing personal, but I noticed that you specifically have a sort of 'fetish' for physical predictions which sound blatantly crazy at first. Why is that? Do you believe that you're helping anybody with saying the potential implications of quantum suicide etc.? What if someone would take your idea literally and do some harm in real world?

In other words, I haven't noticed anything but forceing the most craziest interpretations of physical theories in your posts. Again, why?

 

[mfb]

If there's a suppression of fluctuations to 0 (like in Carroll's paper) it gets from hard to impossible.

See my previous post, the paper is starting with completely different assumptions. In particular, it is starting with a universe that is completely empty.

A BB is still a fluctuation like a person who survives indefinitely.

No it is not, it is completely different.

Anyway, nothing personal, but I noticed that you specifically have a sort of 'fetish' for physical predictions which sound blatantly crazy at first. Why is that? Do you believe that you're helping anybody with saying the potential implications of quantum suicide etc.?

Uh... what?
I like MWI, I think it is very elegant. I don't say it is true, and I'm not even sure if "true" is a meaningful concept for interpretations. I sometimes make posts "within MWI, [...]". I do that for other interpretations as well, maybe not as often as for MWI, but I don't count them. Yes, MWI can have some counterintuitive results, but so does every other interpretation. If you don't like them, that is purely your problem.

What if someone would take your idea literally and do some harm in real world?

I don't see how anyone could use any of my posts as reason to do harm anywhere.

 

[durant35]

See my previous post, the paper is starting with completely different assumptions. In particular, it is starting with a universe that is completely empty.

I think I understand now but I still need to ask you for some clarification. Wouldn't it be more appropriate to say that the paper assumes that the most measure in the branches gets a universe that is completely empty in a finite and relatively expectable time, while there would still be tiny-amplitude branches where the universe would empty out much later, or never in some? And from those assumptions comes the conclusion that when reaching empty universe in a branch there will be no fluctuations.

Bonus-question: will there be decoherence at all in the far future, when the universe gets dark and cold? If yes, can you explain how?

No it is not, it is completely different.

Depends what do you mean by that. Isn't surviving an almost certain death a type of fluctuation? Or the fluctuation that you had in mind is simply spontaneous entropy decrease?

Uh... what?
I like MWI, I think it is very elegant. I don't say it is true, and I'm not even sure if "true" is a meaningful concept for interpretations. I sometimes make posts "within MWI, [...]". I do that for other interpretations as well, maybe not as often as for MWI, but I don't count them. Yes, MWI can have some counterintuitive results, but so does every other interpretation. If you don't like them, that is purely your problem.I don't see how anyone could use any of my posts as reason to do harm anywhere.

I also like some aspects of it but the Born rule problems and the realness of the branches of the type that we've been discussing are certainly a turn off. I hope some further better theory could get rid of these anomalies (I don't know enough about quantum gravity to hypothesize that it could maybe be a solution.)

You are entitled to your opinion of course, and I respect that, I just noticed that your posts sometimes seem too suggestive considering their content. You cannot write 'there is a universe where you will live forever' in the same tone that you can write, for example 'probability is given by the wavefunction squared'. You know physics a lot better than me and you are of course a mentor, but I hope that you can draw the borderline between the seriousness in the content of your posts while differentiating between speculative ideas with no correlation at all with everyday world and what can be established as a fact. That's all, no hard feelings - I respect your patience while answering

 

[PeterDonis]

Wouldn't it be more appropriate to say that the paper assumes that the most measure in the branches gets a universe that is completely empty in a finite and relatively expectable time, while there would still be tiny-amplitude branches where the universe would empty out much later, or never in some?

As far as I can tell, the paper says nothing whatever about this at all. It only talks about a specific state, the de Sitter vacuum, and makes no claims or assumptions whatever about the relative amplitude of that state vs. other possible states.

 

[durant35]

As far as I can tell, the paper says nothing whatever about this at all. It only talks about a specific state, the de Sitter vacuum, and makes no claims or assumptions whatever about the relative amplitude of that state vs. other possible states.

But Sean said many times that our universe will enter de Sitter phase in the far future, and in the paper he mentions the path to get there (excitations leaving the horizon etc.). So he kinda implies what will happen in most branches, as far as I can tell.

 

[PeterDonis]

he kinda implies what will happen in most branches

At most he is kind of implying what will happen in most branches that arise from our current branch. That is very, very different from saying what will happen in most branches arising from whatever the initial wave function of the universe was (which we don't know). Our current branch might not be the one with the most probability amplitude arising from the initial wave function.

 

[durant35]

At most he is kind of implying what will happen in most branches that arise from our current branch. That is very, very different from saying what will happen in most branches arising from whatever the initial wave function of the universe was (which we don't know). Our current branch might not be the one with the most probability amplitude arising from the initial wave function.

Yup. I kinda agree with that. But wouldn't the possibility that you implied kinda be inconsistent with anthtropic reasoning - that we are in this branch because we are likely to be in it.

Btw, this is all assuming that MWI is correct, which for me isn't true. After all, to speak of the initial wavefunction, collapse or whatever on it, as far as I know we should first have a good theory of quantum gravity.

 

[PeterDonis]

wouldn't the possibility that you implied kinda be inconsistent with anthtropic reasoning - that we are in this branch because we are likely to be in it

Not at all. Anthropic reasoning says we are in this branch because we, as sentient observers, have to be in a branch that can contain sentient observers. But it says nothing at all about how likely such branches are compared with branches that cannot contain sentient observers; it just says that, of course, we won't find ourselves in one of the latter branches.

 

[durant35]

Not at all. Anthropic reasoning says we are in this branch because we, as sentient observers, have to be in a branch that can contain sentient observers. But it says nothing at all about how likely such branches are compared with branches that cannot contain sentient observers; it just says that, of course, we won't find ourselves in one of the latter branches.

You're right. Maybe this is too much digression for the thread, but I've read numerous arguments about typicality of our universe in a "multiverse". Translated to the MWI language that should mean that a right cosmologicak theory would put us (hypotethically of course) in a typical branch. Though I agree with your premise, it seems that this should be prioritized.