Zurek's existential interpretation

[naima]

Hi PF

I am reading this paper and this one.

Zurek insists on the fact that pointer states emerge when the same information is imprinted in a huge number of disjoint subsystems of the environment.
Many observers can read those informations and agree with the others.
He never tells what this information is about. He do not says that the observers read a definite output of the measurement.

He says also that after decoherence a collapse of the wave function is not necessary because collapse allready occured.

Do you understand what he really thinks. Copenhague Interpretation has a collapse axiom. He proposes another interpretation, What is his counterpart here?

 

[atyy]

I don't know if Zurek's work is correct, and I don't know if there is a concensus, but I like the approach very much. My understanding is that in his view, decoherence and the imprinting of the information on a huge number of disjoint subsystems of the environment are different. Decoherence alone doesn't cause collapse, but the imprinting leads effectively to collapse.

 

[naima]

Yes this seems attractive. I hope that there are defenders here!

 

[atyy]

We had a discussion some time ago. I don't think we came to any conclusion.

 

[bhobba]

Zurek insists on the fact that pointer states emerge when the same information is imprinted in a huge number of disjoint subsystems of the environment.

Indeed it is quite likely the pointer states emerge in a natural way as Zureck contends. But issues remain such as the so called factorization problem. Most researchers in the area don't seem to think these issues are biggies (and neither do I for what its worth) and they will be resolved in due course - but the claim, as of now, that its true, is not quite correct - more work is required.

Many observers can read those informations and agree with the others.
He never tells what this information is about. He do not says that the observers read a definite output of the measurement.

This is the problem of definite outcomes. Its a REAL big issue in QM and what Zureck is talking about doesn't solve it - further interpretive assumptions are needed for that.

He says also that after decoherence a collapse of the wave function is not necessary because collapse allready occured.

Decoherence explains what is called APPARENT collapse. What it meant is that the system is in what is called an improper mixed state. A mixed stated is where you have a number of systems prepared in a definite state and present one randomly for observation. If an improper mixed state was like that collapse would have occurred - you are observing the system in the state you measured it. But an improper mixed state is different - it has exactly the same mathematical form - and no observation can tell the difference - but it was not prepared that way - an ACTUAL collapse is still required to account for an observation. It has been swept under the carpet so to speak - but its still there.

You will find a detailed discussion here:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

This is the crux of if you think Zureck's approach solves the issues. Are you happy with explaining APPARENT collapse? I personally am - but opinions vary.

Do you understand what he really thinks. Copenhague Interpretation has a collapse axiom. He proposes another interpretation, What is his counterpart here?

The counterpart here is APPARENT collapse - which he considers good enough.

Thanks
Bill

 

[atyy]

Decoherence explains what is called APPARENT collapse. What it meant is that the system is in what is called an improper mixed state. A mixed stated is where you have a number of systems prepared in a definite state and present one randomly for observation. If an improper mixed state was like that collapse would have occurred - you are observing the system in the state you measured it. But an improper mixed state is different - it has exactly the same mathematical form - and no observation can tell the difference - but it was not prepared that way - an ACTUAL collapse is still required to account for an observation. It has been swept under the carpet so to speak - but its still there.

You will find a detailed discussion here:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

This is the crux of if you think Zureck's approach solves the issues. Are you happy with explaining APPARENT collapse? I personally am - but opinions vary.

By Zurek's approach do you mean decoherence and quantum darwinism? I think in more recent work, he's tended to say that decoherence does not lead to apparent collapse, and that quantum darwinism is needed for apparent collapse, and apparent collapse is the only collapse that happens (ie. apparent collapse with decoherence and quantum darwinism = collapse in Copenhagen).

I'm thinking of his terminology in http://arxiv.org/abs/0707.2832 and http://arxiv.org/abs/0903.5082.

 

[bhobba]

By Zurek's approach do you mean decoherence and quantum darwinism? I think in more recent work, he's tended to say that decoherence does not lead to apparent collapse, and that quantum darwinism is needed for apparent collapse, and apparent collapse is the only collapse that happens (ie. apparent collapse with decoherence and quantum darwinism = collapse in Copenhagen).

I haven't kept up with Zureck's Quantum Darwinism stuff so can't really comment on his latest views.

But I think most physicists believe decoherence does lead to apparent collapse - I certainly do eg as detailed in Schlosshauer's textbook on decoherence which is my go-to book on such things.

But is apparent collapse enough? That's the 64 million dollar question isn't it.

I believe it is - but opinions vary and discussions on it can get quite heated so I don't want to go down that path, except to again reiterate - opinions vary.

Thanks
Bill

 

[kith]

Indeed it is quite likely the pointer states emerge in a natural way as Zureck contends. But issues remain such as the so called factorization problem.

In http://arxiv.org/abs/0707.2832, Zurek uses the explicit "zeroth" axiom "The universe consists of systems."

 

[bhobba]

In http://arxiv.org/abs/0707.2832, Zurek uses the explicit "zeroth" axiom "The universe consists of systems."

Indeed.

But, as he states, its often omitted as obvious - which it pretty much is.

Anyway that's not strictly the factorization issue - which is the physics does not depend on how we partition those systems conceptually - which to me is just as obvious.

Thanks
Bill

 

[atyy]

I haven't kept up with Zureck's Quantum Darwinism stuff so can't really comment on his latest views.

But I think most physicists believe decoherence does lead to apparent collapse - I certainly do eg as detailed in Schlosshauer's textbook on decoherence which is my go-to book on such things.

But is apparent collapse enough? That's the 64 million dollar question isn't it.

I believe it is - but opinions vary and discussions on it can get quite heated so I don't want to go down that path, except to again reiterate - opinions vary.

By "apparent collapse" you mean either a form of many-worlds or Bohmian mechanics?

 

[bhobba]

By "apparent collapse" you mean either a form of many-worlds or Bohmian mechanics?

I certainly agree these terms are a bit vague.

In MW no collapse actually occurs so most definitely it can be considered apparent.

In BM collapse actually does occur, but its a bit of a complicated issue from what I can gather:
http://arxiv.org/pdf/quant-ph/0611032v1.pdf

However I am not expert enough in it to discuss the details - all I can do is point to the above paper. We have a number of posters who are though, so they can perhaps chime in.

The sense I mean it is as per the following link:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

Its that an improper mixture is observationally indistinguishable from a proper one. If it was a proper one collapse would have occurred and the observation reveals what's there. It isn't, but because it looks like it, its apparent.

Thanks
Bill

 

[Quantumental]

The weird thing about Zurek's view is that he isn't a MWI proponent, instead he believes information might be fundamental

 

[naima]

information as fundamentel why not?

The problem with Zurek is that he tells us that the consensus about reality comes from the huge number of the same information in environment sub systems.
every observer read the same thing. Why has he to go further? Mass is said.
I found in Rovelli another way to speak.
Experiment gives the answer to a set of one bit questions. There is a matrix which relates this set of bits to the bits of another question (another experiment. he reconstructs QM without state function.
Skip to III.

 

[atyy]

I certainly agree these terms are a bit vague.

In MW no collapse actually occurs so most definitely it can be considered apparent.

In BM collapse actually does occur, but its a bit of a complicated issue from what I can gather:
http://arxiv.org/pdf/quant-ph/0611032v1.pdf

However I am not expert enough in it to discuss the details - all I can do is point to the above paper. We have a number of posters who are though, so they can perhaps chime in.

The sense I mean it is as per the following link:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

Its that an improper mixture is observationally indistinguishable from a proper one. If it was a proper one collapse would have occurred and the observation reveals what's there. It isn't, but because it looks like it, its apparent.

Thanks
Bill

I usually think of collapse as the process that produces definite outcomes (for an observer). Hansen's essay says that decoherence is generally thought not solve the problem of definite outcomes. He says on p40,"Decoherence theorists have generally come to accept the criticisms above, and accept that decoherence alone does not solve the problems of outcomes, and therefore leaves the most essential question untouched." So presumably by apparent collapse you don't mean the process that produces apparent definiteness for each observer?

 

[bhobba]

I usually think of collapse as the process that produces definite outcomes (for an observer). Hansen's essay says that decoherence is generally thought not solve the problem of definite outcomes. He says on p40,"Decoherence theorists have generally come to accept the criticisms above, and accept that decoherence alone does not solve the problems of outcomes, and therefore leaves the most essential question untouched." So presumably by apparent collapse you don't mean the process that produces apparent definiteness for each observer?

Lets be clear. Decoherence does NOT solve the measurement problem. The collapse is still there - but hidden. It leaves the problem of definite outcomes untouched - you need further assumptions to resolve that.

But also be clear what it DOES solve. There is no way, no way at all, to observationally tell an improper mixture from a proper one. If it was a proper one then a specific outcome would have been selected and randomly presented for observation. The problem of outcomes solved, reality is there prior to observation - all issues taken care of. This is why it APPARENTLY solves the problem.

Of course I do not expect anyone to believe as I do that is good enough. But what I would like understood is all you have to do is add an interpretive assumption, an example of which is, since we can't tell a difference, then we as human beings, naturally interpret it as an actual collapse since that's how our brains are wired, and the problem is solved. That just one example - another is MWI where no collapse actually occurs and each 'outcome' of the improper mixture is considered a separate world and continues to evolve. Still another is Decoherent Histories. There are undoubtedly tons of other ways to resolve the issue. Another one I want to investigate is a variant of TI a poster here pointed me to where he thinks QFT has an actual mechanism to single one out:
https://www.amazon.com/dp/0521764157/?tag=pfamazon01-20

The point though is most would think progress has been made, and its now a lot clearer what's actually going on with collapse. We have an explanation for APPARENT collapse and that is definitely a worthwhile development I honestly believe everyone into QM should be aware of.

That's why I always suggest anyone interested in the foundations of QM get a hold of Schlosshauer's text:
https://www.amazon.com/dp/3540357734/?tag=pfamazon01-20

Not only is decoherence interesting in its own right, but Schlosshauer very carefully explains its interpretive implications, as well as open issues.

Thanks
Bill

 

[atyy]

@bhobba, I think I understand you, except we have a terminology difference. Can I just check that in Hansen's terminology http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf (p31), there are 5 parts to the measurement problem, and in your understanding, decoherence solves parts (iii), (iv) and (v) but leaves (i) and (ii) unanswered?

 

[Quantumental]

Bhobba: if you have read Hansen's paper, I wonder what you think of the conclusion that decoherence is not enough for MWI?

 

[bhobba]

@bhobba, I think I understand you, except we have a terminology difference. Can I just check that in Hansen's terminology http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf (p31), there are 5 parts to the measurement problem, and in your understanding, decoherence solves parts (iii), (iv) and (v) but leaves (i) and (ii) unanswered?

The reason I give the link to Hensen's paper is I have gone through it and agree with it.

He is correct. It is virtually exactly the same as Schlosshauer's book, but that has a lot more detail as well as a more careful analysis.

But what Hensen doesn't point out, and in fact, believe it or not, is another reason why I like to link to it, is while it leaves the central issue untouched, it has recast it in a form that many such as myself believe is much more amenable to a reasonable interpretive assumption such as the ignorance ensemble interpretation he mentions, and I hold to, that, while skirting the central issue, begs the question - is it worth worrying about? I don't want to argue that, because in the past it has led to some rather heated discussion, with some misinterpreting what I am saying. I would much rather people think about it themselves and reach their own conclusion.

Thanks
Bill

 

[atyy]

The reason I give the link to Hensen's paper is I have gone through it and agree with it.

He is correct. It is virtually exactly the same as Schlosshauer's book, but that has a lot more detail as well as a more careful analysis.

But what Hensen doesn't point out, and in fact, believe it or not, is another reason why I like to link to it, is while it leaves the central issue untouched, it has recast it in a form that many such as myself believe is much more amenable to a reasonable interpretive assumption such as the ignorance ensemble interpretation he mentions, and I hold to, that, while skirting the central issue, begs the question - is it worth worrying about? I don't want to argue that, because in the past it has led to some rather heated discussion, with some misinterpreting what I am saying. I would much rather people think about it themselves and reach their own conclusion.

Thanks
Bill

As far as I can tell, I too agree with Hansen. :) I can't tell if I agree with you. The reason is quantum mechanics. If I look at Hansen, I will collapse it. Now, when you measure Hansen, you may get a different result. :p

 

[bhobba]

Bhobba: if you have read Hansen's paper, I wonder what you think of the conclusion that decoherence is not enough for MWI?

Well it isn't eg the Born rule somehow needs to be derived in a deterministic theory and that is a whole other issue interdependent of decoherence.

We have had a very long thread on that that can be googled - I don't want to go through it again - the central issue is even in a deterministic theory one can use Bayesian hypothesis testing to arrive at statements about the outcomes of observations. Gleason's theorem, and other methods also exist, can be used to give the Born rule as the most reasonable level of confidence used in that Bayesian approach. Specifically it proves it's the only one that is basis independent, which is really one of the main things about vector spaces - the physics should not really depend on a specific basis, so the confidence you are in a particular world shouldn't really either. Of course that is an assumption independent of decoherence.

Thanks
Bill

 

[bhobba]

As far as I can tell, I too agree with Hansen. :) I can't tell if I agree with you. The reason is quantum mechanics. If I look at Hansen, I will collapse it. Now, when you measure Hansen, you may get a different result. :p

Mate - that's why, rather than discussing it I link to the paper - you can form your own view.

I hold to the ignorance ensemble interpretation in that paper, and for me, I have zero problem with the fact that interpretation does not say how a particular outcome is selected ie the problem of outcomes is simply side stepped. That's simply my view - but I don't want to argue about it.

Thanks
Bill

 

[naima]

information as fundamentel why not?

The problem with Zurek is that he tells us that the consensus about reality comes from the huge number of the same information in environment sub systems.
every observer read the same thing. Why has he to go further? Mass is said.

Maybe i am wrong here. Suppose one finds a way to erase all the informations in the subsystems. Would the "before collapse" state reappear?

 

[naima]

Kye opened a thread on this question.
He had a positive answer.

 

[atyy]

Maybe i am wrong here. Suppose one finds a way to erase all the informations in the subsystems. Would the "before collapse" state reappear?

I guess the clearest (for me so far) way to understand the quantum darwinism is within Many-Worlds (but then it's not so attractive for me). However, at the end of http://arxiv.org/abs/0707.2832 Zurek writes "Our "existential interpretation" is in that sense not an interpretation ..." and "It is therefore not clear whether one is forced to attribute "reality" to all of the branches of the universal state vector."

A more recent paper by Jess Riedel, Zurek and Zwolak "The Rise and Fall of Redundancy in Decoherence and Quantum Darwinism" http://arxiv.org/abs/1205.3197 seems to deal with some aspects of the loss of redundancy. At the end they say "A large molecule localized through collisional decoherence by photons is immersed in an environment with insignicant mixing [40], and so is recorded redundantly [15, 16], but a lone argon atom in a dense nitrogen gas is not. Whether an essentially unique quasi-classical realm [41, 42] can be identied from such principles is a deep, open question [43, 44] about the quantum-classical transition."

Kye opened a thread on this question.
He had a positive answer.

I'd forgotten about that. It's really interesting.