Quantum Suicide: Why is only experimenter convinced?

[zonde]

I think quantum suicide experiment is very poor starting point for any scientific discussion as this experiment is not scientific.
I see at least three problems. First, it does not allow falsification of MWI - if someone sees "experimenter" dead he shouldn't consider MWI false. Second, it relays on biased sample (even if MWI is considered confirmed) - at the end we consider one world where "experimenter" has survived while we say nothing about any other world. Third, scientific community does not gain any knowledge - idea of experiment is that MWI is confirmed only for "experimenter".

 

[Demystifier]

For my own critique of the quantum suicide experiment see
https://www.physicsforums.com/threads/critique-of-the-quantum-suicide-experiment.526213/

In short, even the experimentalist should not be convinced by his own survival, provided that he is rational.

Let me present one additional argument. Assume that the experimenter believes that MWI is wrong, but that the invisible pink elephant-angel protects him. Each time he survives (for whatever reason), he will be more and more convinced that his belief is correct. Does it make his belief justified?

 

[Quantumental]

I think my issue of divergence vs splitting should be given more consideration within the MWI community as it directly falsifies all forms of Quantum Immortality instantly and is also the metaphysical view argued for by the leaders of modern Everett reading.

 

[Demystifier]

Quantumental, the splitting interpretation is motivated by decoherence. What is the motivation for the divergence interpretation?

 

[atyy]

Regarding the quantum suicide experiment, I see a big practical problem: if you try to shoot yourself, the probability that you survive the experiment in a severely injured state is much higher than the probability that the bullet tunnels through your head. So even if the experiment works like proponents claim, I don't think that you can repeat it.

Tegmark pointed out that death is rarely a binary event. It was someone else who devised the quantum suicide thought experiment. I don't recall who.

The truth is, for every world where we cheat death, there is an overwhelming number where we barely cling to life, in pain, barely conscious. Immortality with the ultimte price.

If there is a state dead that is orthogonal to the state alive, and given the initial setup states are orthogonal, could one use that unitarity preserves orthogonality to argue that the other possibilities are never seen? The main problem, of course, is preparing yourself in the same state every time. But should be doable in principle.

 

[atyy]

I think my issue of divergence vs splitting should be given more consideration within the MWI community as it directly falsifies all forms of Quantum Immortality instantly and is also the metaphysical view argued for by the leaders of modern Everett reading.

Isn'tt that just Bohmian MWI? In Bohmian MWI, I think one still survives in at least one world.

 

[craigi]

If there is a state dead that is orthogonal to the state alive, and given the initial setup states are orthogonal, could one use that unitarity preserves orthogonality to argue that the other possibilities are never seen? The main problem, of course, is preparing yourself in the same state every time. But should be doable in principle.

This is a direction I'd really like the thread to take.

It is, as you suggest, possible to create a reversible observer. Because we, as humans generate so much heat and entropy, we're statistically very unlikely to ever return to the state which we were in before measurement. However, in principle, we should be able to create an extremely efficient observer, which is thermodynamically reversible. This observer could make a measurement on a quantum system, then revert its state, to test if the state of the observed system is actually relative to the state of the observer. In my view, this can prove the correctness of the MWI interpretation, not just as an interpretation, but as a theory, not only to the observer, but also to the scientific community.

If the MWI is proven to be true, then we may have to conclude that the somewhat daunting implications of the quantum suicide thought experiment are indeed correct too and that consiousness is a permanent state.

 

[Quantumental]

Quantumental, the splitting interpretation is motivated by decoherence. What is the motivation for the divergence interpretation?

Saunders has a whole chapter in the "Many Worlds?" volume about it which can be read here: http://users.ox.ac.uk/~lina0174/chance.pdf

ctrl + f: diverge

 

[kith]

If there is a state dead that is orthogonal to the state alive, and given the initial setup states are orthogonal, could one use that unitarity preserves orthogonality to argue that the other possibilities are never seen?

If you model the situation with two orthogonal states |alive> and |dead>, there seems to be no problem. But my point was that such a model misses the crucial point of repeatability. A reasonable model has to include at least the three possible outcome states |alive and reasonable well>, |alive and severely injured> and |dead>.

 

[atyy]

If you model the situation with two orthogonal states |alive> and |dead>, there seems to be no problem. But my point was that such a model misses the crucial point of repeatability. A reasonable model has to include at least the three possible outcome states |alive and reasonable well>, |alive and severely injured> and |dead>.

Just get a fantastic experimentalist to do it, not a theorist like Tegmark. Of course, no experimentalist would be sensible enough to try. Oh, maybe in many worlds there would be one.

 

[zonde]

However, in principle, we should be able to create an extremely efficient observer, which is thermodynamically reversible.

No, because observation means creation of irreversible record. Of course you can erase record but you can't undo record. If you can undo it then it's not record.

 

[bhobba]

Saunders has a whole chapter in the "Many Worlds?"

I had a quick look.

Its philosophical waffle devoid of any actual physics as far as I can see. So I looked up Saunders - he is a philosopher.

You asked why physicists don't take it seriously - unless you can explain the actual physics then you have your answer.

As Demystifyer said - exactly how does 'divergence' differ from interpreting each part of an improper mixed state as a separate world?

Thanks
Bill

 

[craigi]

No, because observation means creation of irreversible record. Of course you can erase record but you can't undo record. If you can undo it then it's not record.

So, if I understand you correctly, then your thesis is that a reversible system can't make a measurement of a separate quantum system. Is that right?

 

[Quantumental]

I had a quick look.

Its philosophical waffle devoid of any actual physics as far as I can see. So I looked up Saunders - he is a philosopher.

You asked why physicists don't take it seriously - unless you can explain the actual physics then you have your answer.

As Demystifyer said - exactly how does 'divergence' differ from interpreting each part of an improper mixed state as a separate world?

Yes, he is a philosopher, but this is still his expertise. I don't like your attitude of dismissing everyone who got their degree in philosophy of physics.
David Wallace talks about this exact view in the book too and he got a PhD in physics as well as a PhD in philosophy, so if Saunders' or Alastair Wilson's status is the issue, now it should be no more..
The point is that divergence vs splitting is undetermined by physics, which is why you have to go into the realm of philosophy to lean either direction.

I don't see how the physics tell you that splitting takes place at all

 

[bhobba]

I don't like your attitude of dismissing everyone who got their degree in philosophy of physics.

That's not my issue.

It's when you link to an article, I go to the trouble of wading through it only to find its philosophical waffle, which in this case is mostly rhubarb about what probability is.

All I am asking is you give an overview of what it's about concentrating on the physics. If for some reason you find that difficult then its not really suitable for this forum that discusses physics - not philosophy.

IMHO this whole thread is philosophical BS leaning heavily on a feeling we have about death - namely you can't experience death - so the argument isn't symmetrical. We don't know you don't experience death - and that isn't even examining the issue of if QM requires the experiencing of anything by a conscious observer - which of course it doesn't.

Thanks
Bill

 

[bhobba]

I don't see how the physics tell you that splitting takes place at all

The physics doesn't tell you anything about interpretation - which is why they are interpretations.

But in discussion of interpretations here we focus on the physical consequences eg for MW its what the consequence of interpreting the mixed state after decoherence as separate worlds. What you linked to, as far as I can see, simply is a philosophical discussion trying to justify the idea of future probabilities. That's not really germane to the physics ie after decohertence the worlds split.

Thanks
Bill

 

[Quantumental]

The physics doesn't tell you anything about interpretation - which is why they are interpretations.

But in discussion of interpretations here we focus on the physics eg for MW its what the consequence of interpreting the mixed state after decoherence as separate worlds. What you linked to, as far as I can see, simply is a philosophical discussion trying to justify the idea of future probabilities. That's not really germane to the physics ie after decohertence the worlds split.

Did you read the section of Overlap vs Divergence? This is where he makes his argument

 

[bhobba]

Did you read the section of Overlap vs Divergence? This is where he makes his argument

Why don't you summarise it?

I am afraid things like the following make my eyes roll back:
'On the other hand S1 is on the face of it just a semantic rule—it is merely a linguistic matter. The referents of terms are constrained by their contexts of use, granted; but over and above those constraints, not even in the God’s-eye view is their meaning determined. It is up to us to say what, precisely, among the structures in the universal state, our words really mean. And if that is all there is to uncertainty, nothing much should hang on the matter either way. The challenge remains: to justify the probability interpretation of EQM on the grounds of (i) and (ii) alone'

Physics is not about linguistics and semantics - in fact it about the exact opposite.

Thanks
Bill

 

[zonde]

So, if I understand you correctly, then your thesis is that a reversible system can't make a measurement of a separate quantum system. Is that right?

Yes, that's right.

 

[bhobba]

No, because observation means creation of irreversible record.

That's not quite true eg in the quantum eraser decoherence is undone.

The modern view of observation is after decoherence. In most cases that is irreversible, but in some simple contrived cases it can be reversed.

Thanks
Bill

 

[zonde]

That's not quite true eg in the quantum eraser decoherence is undone.

In quantum eraser interference pattern is recovered in subensembles after detections with recorded timestamps are already made. It's hard to understand how do you interpret that as "decoherence is undone".

The modern view of observation is after decoherence.

If decoherence is modeled as interaction with environment i.e. certain physical process and not just interpretation, then it's subject to experimental verification.

 

[craigi]

Yes, that's right.

So we really need to review some of the recent literature. I don't have time to do that right now, but you'll be interested in Deutsch's paper entitled, "Quantum Theory as a Universal Physical Theory". I won't link it, because I think it's supposed to be behind a paywall.

 

[zonde]

So we really need to review some of the recent literature. I don't have time to do that right now, but you'll be interested in Deutsch's paper entitled, "Quantum Theory as a Universal Physical Theory". I won't link it, because I think it's supposed to be behind a paywall.

You can quote relevant arguments from Deutsch's paper.
Meanwhile I will give my argument. Results of observations and measurements can be shared, it means they can be copied without limit. Given theoretically unlimited number of possible copies (and copies of copies) how you can undo measurement?

 

[bhobba]

In quantum eraser interference pattern is recovered in subensembles after detections with recorded timestamps are already made. It's hard to understand how do you interpret that as "decoherence is undone".

Its well known:
https://www.physicsforums.com/threa...and-the-delayed-choice-quantum-eraser.623648/

If decoherence is modeled as interaction with environment i.e. certain physical process and not just interpretation, then it's subject to experimental verification.

Of course.

Thanks
Bill

 

[zonde]

Its well known:
https://www.physicsforums.com/threa...and-the-delayed-choice-quantum-eraser.623648/

Of course.

Well you are using decoherence in two different senses and you mix them in your arguments. It's very hard to have any discussion with you because of that.
There is decoherence as absence of coherence in beam of light (it does not show interference).
And there is decoherence as a hypothesis that explains something about measurement.

There are not much questions about one meaning as it is defined directly from observations.
The other one is rather speculative.

 

[bhobba]

Well you are using decoherence in two different senses and you mix them in your arguments

I am only using it in one sense as per the following:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

I can't ever recall it being used in the sense of photon coherence.

Thanks
Bill

 

[zonde]

I am only using it in one sense as per the following:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

Your source says that nowadays there is more than one sense for "decoherence".
"However, “decoherence” is now often used for a much more general idea, namely that of the environment-induced decoherence program, referring not only to the effect of decoherence itself, but also referring to
• its main cause, the ubiquitous and almost unavoidable interaction of a quantum system with its environment;
• its physical implications, expressed in predictions for empirically verifiable experiments;
• its conceptual implications, on for instance the traditional problem of quantum measurement, and the emergence of the classical world from a quantum reality.
It is important to distinguish between these last two points, because although the relevance of environment-induced decoherence on empirical outcomes is widely acknowledged, its conceptual implications are subject to much more controversy. Opinions range from solving (part of) the measurement problem, as founding decoherence theorists used to claim, to denying any conceptual implications apart from those illustrated any other quantum mechanical calculation."

I can't ever recall it being used in the sense of photon coherence.

When you refer to quantum eraser experiment you mean decoherence as our ability to see/not see interference pattern. When you say that decoherence can be undone you do not mean that measurement of individual photons can be undone.

 

[bhobba]

When you refer to quantum eraser experiment you mean decoherence as our ability to see/not see interference pattern. When you say that decoherence can be undone you do not mean that measurement of individual photons can be undone.

I mean the entanglement that allows us to determine which path information.

Thanks
Bill