New experimental proof of wave-function collapse?

[Edward Wij]

Yes - its her view - not mine. She believes its a major assumption that the environment in deocherence modells is modeled randomly - I don't.

Thanks
Bill

In your thread with her. I thought you were agreeing with her. You said "Its a general assumption. For example do you believe stray photons from the CBMR interacting with a dust particle are entangled?"

She answered "But it's an assumption you're not allowed to make in order to derive decoherence, because it implicitly injects decoherence from the start. Yes, as I've said, of course things like stray photons are decohered, but that's an empirical observation that can't be used in order to theoretically 'derive' our empirical observation from only the Schrödinger evolution without any actual collapse that could really decohere things. That's why it's circular.

You didn't reply after it. So thought you were agreeing with her. Can you state the reason why you don't believe it?

 

[bhobba]

Can you state the reason why you don't believe it?

The number of random states is much much greater than those that are ordered. Its a very common assumption made in mathematical modelling all the time. Its an assumption - yes - but a very very reasonable one.

The reason I didn't reply is it would likely go nowhere degenerating into a view of assumptions in mathematical models. My background is applied math where mathematical models are very common as well as the assumptions they make. I have my view - she has hers.

Thanks
Bill

 

[Edward Wij]

The number of random states is much much greater than those that are ordered. Its a very common assumption made in mathematical modelling all the time. Its an assumption - yes - but a very very reasonable one.

Thanks
Bill

But she has addressed it in a thread I read again and again.. She said "Bill the whole point is that you can't apply 'ordinary statistical thinking' and assume 'random systems' with 'random phases' because quantum theory with only Schrödinger evolution doesn't license that. This is the circularity issue. In QM with only Sch. evolution there are no 'stray photons' unless you assume they are 'stray' (i.e, already have randomized phases) from the beginning. All the talk of this or that random dust particle or stray photon is circular. Yes these are all stray and decohered but not because of 'decoherence derivation' which assumes that from the beginning. In fact all these stray objects are decohered *because* there is real collapse. 'Apparent collapse' into the preferred basis is circular and doesn't explain anything."

Well?

 

[bhobba]

But she has addressed it in a thread I read again and again.. She said "Bill the whole point is that you can't apply 'ordinary statistical thinking' and assume 'random systems' with 'random phases' because quantum theory with only Schrödinger evolution doesn't license that.

Edward - I don't agree with her and have told you why. I believe ordinary statistical thinking is applicable. BTW my view is the orthodox one - hers isn't.

Do you believe, for example, if you observe stray photons around you they will have any order? She believes such requires explanation - I don't. There is a very powerful theorem called the Central Limit Theorem that says, basically, if something is determined by many random factors of any distribution, it must follow a certain distribution. Do you really believe things you find in the environment have not been subjected to many random factors?

Thanks
Bill

 

[Edward Wij]

Edward - I don't agree with her and have told you why. I believe ordinary statistical thinking is applicable. BTW my view is the orthodox one - hers isn't.
Do you believe, for example, if you observe stray photons they will have any order? She believes such requires explanation - I don't.

Thanks
Bill

Ok. I'll think of your objection. Why didn't you mention it last year in the thread with her this objection. It seems this is the first time you mentioned this.

 

[bhobba]

Ok. I'll think of your objection. Why didn't you mention it last year in the thread with her this objection. It seems this is the first time you mentioned this.

The reason I didn't reply is it would likely go nowhere degenerating into a view of assumptions in mathematical models. My background is applied math where mathematical models are very common as well as the assumptions they make. I have my view - she has hers.

I elucidated my view of why that assumption is very common - see my previous post.

Thanks
Bill

 

[Edward Wij]

I elucidated my view of why that assumption is very common - see my previous post.

Thanks
Bill

Ok. This is all very important so hope others can rephrase what Bill is saying in their language. The reason this is important is because if Rkastner is (in case) right.. decoherence is just secondary. Underneath is a real objective collapse that many authors love (like the reference the OP of this thread is attributing to).

This reminds me of Penrose. His spacetime collapsing wave function makes sense. Think of wave functions as all pure state. Then you have spacetime that collapse the wave function. Spacetime is discrete so it can be the natural collapser of wave functions!

 

[bhobba]

This is all very important

You do understand that this is a minority view? That doesn't make it incorrect of course - just there is likely a reason it hasn't garnished support.

Its similar to the following objection against many worlds:
http://arxiv.org/pdf/1210.8447v1.pdf

Added Later:
One thing to remember is there is an inherent randomness in QFT - for example spontaneous emission is explained by interaction with the vacuum and vacuum fluctuations that are random. That would seem to be the ultimate source of randomness.

Thanks
Bill

 

[uumlau]

Speaking of Matrix. Guys. Why is it valid to consider Many Worlds or Bohmian Mechanics or even Transactional Interpretation.. while physicists want to ignore the Matrix Interpretations? Did you notice many worlds or bohmians are Newtonian like in which you want to attribute the wave functions have trajectories or the branches real? Why not just consider the wave function as just part of the software or algorithm used by reality. Then it doesn't have to be Bohmians or Many worlds. It is just a program.. obsevations or measurements are just interactions in the program.. problem solved. If you consider this philosophy and avoided thinking of it, isn't Many worlds or Bohmian mechanics philosophy too since it has same prediction as QM and no new predictions? Note I'm not trying to discuss philosophy.. just want to know why Bohmians or Many worlds and even Consistent Histories are valid interpretations while the Matrix (reality created by program) Interpretation is automatically shutted out. Could anyone explain so I know? Knowing how the algorithm or the program work in the Matrix Intepretations can even solve key physics problems like quantum gravity, the hierarchy problems, etc.

Or, why have an "interpretation" at all?

Answer: because quantum mechanics doesn't allow one to apply the same intuitions as classical mechanics, so people try to explain how it works in a more-or-less "classical" way. Looking at the world as a simulation, while kind of nonsensical, at least has one virtue: there is no explanation as to "why" things have to work one way or another. And while sometimes our math is very precise, much of it is going to be approximate.

Here's another analogy for pretending that "wave function collapse" actually means anything. Let's say that I'm putting apples into a basket. I use the "addition function" to describe the accumulation of apples. I put in 3, then I put in 8 and then I put in 4, and the addition function correctly describes 15 apples. If I reach into the basket, eat an apple, and toss the core back into the basket, that doesn't mean that the "addition function collapsed". Rather, it means that something happened that addition does not describe. In quantum mechanics, every case of "wave function collapse" involves the system being altered in a way that is not described by the (prior) wave function.

 

[atyy]

In fact, it seems that some of them consider it seriously:
http://phys.org/news/2012-10-real-physicists-method-universe-simulation.html

There's no proof that it can be done - unless lattice chiral fermions are possible

 

[atyy]

What is mostly taught to undergraduates is the shut-up-and-calculate interpretation.

Well, at least 2 classics mention Bohr or Copenhagen - Landau and Lifshitz and Messiah. LL was what I read when I first learned QM (together with French and Taylor, and Gasiorowicz) Actually, Messiah was a recommended text for one of the courses I took, but I never read it till recently, and it's interesting that he writes that hidden variables may be possible, but he will just take Copenhagen since there is no evidence against it yet. He doesn't quite say hidden variables but his two options are Einstein and Copenhagen, and I interpret Einstein's approach as hidden variables.

 

[rootone]

In fact, it seems that some of them consider it seriously:
http://phys.org/news/2012-10-real-physicists-method-universe-simulation.html

Isn't this just kicking the can further down the road though?
If what we experience is a simulation, then what is it simulating?

 

[ddd123]

Isn't this just kicking the can further down the road though?

Pretty much.

If what we experience is a simulation, then what is it simulating?

Or rather, what is it that is simulating? Are they simulated too? And so on. But I tend to lean more on the idea that these people don't really take this too seriously but are just having some fun. At least, I hope so.

 

[Edward Wij]

Edward - I don't agree with her and have told you why. I believe ordinary statistical thinking is applicable. BTW my view is the orthodox one - hers isn't.

Do you believe, for example, if you observe stray photons around you they will have any order? She believes such requires explanation - I don't. There is a very powerful theorem called the Central Limit Theorem that says, basically, if something is determined by many random factors of any distribution, it must follow a certain distribution. Do you really believe things you find in the environment have not been subjected to many random factors?

Thanks
Bill

I'd like to comprehend how exactly yours differs to Ruth in terms of the language of density matrix (i'm familiar with the math). When we treat a subsystem, we know the phases are not in coherence (because you ignore the rest of the system). Therefore two stray photons won't be in coherence. Of course. Are you saying that Ruth believes they are in coherence? Or maybe there is some confusion or misunderstanding in the discussion especially when something this basic and obvious. Maybe she is just focusing on the collapse part or born rule and arguing born rule must be fully applied for there to be classical outcome? I'm familiar with the math of it. So please tell me in math terms how exactly she may differ to yours and if it could just be because of the focus like I just mentioned. Thanks.

 

[bhobba]

I'd like to comprehend how exactly yours differs to Ruth in terms of the language of density matrix (i'm familiar with the math). When we treat a subsystem, we know the phases are not in coherence (because you ignore the rest of the system).

Ruth and I do not differ on any of the technical detail. Its simply the interpretation. If you go and look at some specific decoherene models then you will see there is an assumption (in some of them any way) of the environment being random. She does not dispute that being true - what she disputes is its a reasonable assumption that more or less is implied by the nature of QM - eg what I mentioned before about quantum fluctuations in the vacuum leading to an inherent randomness. She thinks it a big question mark the theory needs to explain. I don't agree.

Added Later:
If you want to understand the situation you must investigate the detail. The following is the best source I know that starts from only basic knowledge and builds up to it in the final chapters:
http://quantum.phys.cmu.edu/CQT/index.html

The relevant chapter is chapter 26 at the end:
http://quantum.phys.cmu.edu/CQT/chaps/cqt26.pdf

See section 26.4 - The Random Environment. Ruth thinks the assumption it being random, while true, requires explanation. Me, and I suspect others as well, think its a result of the usual quantum randomness such as, for example, found in spontaneous emission and explained by vacuum fluctuations. The environment will have been subjected to such so frequently it will be well and truly scrambled, especially considering the Central Limit Theorem I mentioned previously.

Also, please, please, if you want to discuss that chapter put the time and effort into reading all the previous ones.

Thanks
Bill

 

[Edward Wij]

Ruth and I do not differ on any of the technical detail. Its simply the interpretation. If you go and look at some specific decoherene models then you will see there is an assumption (in some of them any way) of the environment being random. She does not dispute that being true - what she disputes is its a reasonable assumption that more or less is implied by the nature of QM - eg what I mentioned before about quantum fluctuations in the vacuum leading to an inherent randomness. She thinks it a big question mark the theory needs to explain. I don't agree.

Thanks
Bill

In the thread last year. She was discussing about the factoring problem with you or how you decompose system and environment.. because if the decomposition differs.. decoherence may have different predictions. Is the factoring problem related to quantum fluctuations in vacuum leading to inherent randomness? Would this solve the factoring problem?

 

[bhobba]

In the thread last year. She was discussing about the factoring problem with you or how you decompose system and environment.. because if the decomposition differs.. decoherence may have different predictions. Is the factoring problem related to quantum fluctuations in vacuum leading to inherent randomness? Would this solve the factoring problem?

I don't believe there is a factoring problem - note the word MAY lead to different predictions. I haven't seen two different analysis of the same situation leading to different predictions. Although I do recall in one discussion about it someone did show it happens in classical mechanics. My view, as I have mentioned many times, is I think some key theorems are required to settle the issue one way or another. That's my view - there are others. They have been thrashed out before and I will not be drawn into it again.

For definiteness I will refer to the following:
http://arxiv.org/pdf/1210.8447v1.pdf

Its saying nothing can happen in MW. Yet we have things like vacuum fluctuations causing inherent randomness. Since MW is cooked up to be indistinguishable from standard QM it should include that. So I don't necessarily accept that papers analysis as correct. In saying that, I am appealing to Quantum Field Theory which I am not as familiar with as I would like. I would like someone with more knowledge of QFT to comment of the exact cause of random vacuum fluctuations.

Thanks
Bill

 

[Edward Wij]

I don't believe there is a factoring problem - note the word MAY lead to different predictions. I haven't seen two different analysis of the same situation leading to different predictions. Although I do recall in one discussion about it someone did show it happens in classical mechanics. My view, as I have mentioned many times, is I think some key theorems are required to settle the issue one way or another. That's my view - there are others. They have been thrashed out before and I will not be drawn into it again.

For definiteness I will refer to the following:
http://arxiv.org/pdf/1210.8447v1.pdf

Its saying nothing can happen in MW. Yet we have things like vacuum fluctuations causing inherent randomness. Since MW is cooked up to be indistinguishable from standard QM it should include that. So I don't necessarily accept that papers analysis as correct. In saying that, I am appealing to Quantum Field Theory which I am not as familiar with as I would like. I would like someone with more knowledge of QFT to comment of the exact cause of random vacuum fluctuations.

Thanks
Bill

Zurek and Maximillian never mentioned about the factoring problem? If you have heard them mentioning it.. let me know. They are the authority. Maybe factoring problem is only valid in Many Worlds as acknowledged by Wallace? Who are the decoherence authors who acknowledge there is factoring problem? Is it only Ruth?

 

[atyy]

Zurek and Maximillian never mentioned about the factoring problem? If you have heard them mentioning it.. let me know. They are the authority. Maybe factoring problem is only valid in Many Worlds as acknowledged by Wallace? Who are the decoherence authors who acknowledge there is factoring problem? Is it only Ruth?

Zurek and Schlosshauer do mention the factoring problem - whether it is a problem depends on what interpretation one is using.

Schlosshuaer, http://arxiv.org/abs/quant-ph/0312059
p8: Also, there exists no general criterion for how the total Hilbert space is to be divided into subsystems, while at the same time much of what is called a property of the system will depend on its correlation with other systems. This problem becomes particularly acute if one would like decoherence not only to motivate explanations for the subjective perception of classicality (as in Zurek’s “existential interpretation,” see Zurek, 1993, 1998, 2003b, and Sec. IV.C below), but moreover to allow for the definition of quasiclassical “macrofacts.” Zurek (1998, p. 1820) admits this severe conceptual difficulty: In particular, one issue which has been often taken for granted is looming big, as a foundation of the whole decoherence program. It is the question of what are the “systems” which play such a crucial role in all the discussions of the emergent classicality. (. . . ) [A] compelling explanation of what are the systems—how to define them given, say, the overall Hamiltonian in some suitably large Hilbert space—would be undoubtedly most useful.

Zurek, http://arxiv.org/abs/quant-ph/9805065
p2: We can mention two such open issues right away: Both the formulation of the measurement problem and its resolution through the appeal to decoherence require a Universe split into systems. Yet, it is far from clear how one can define systems given an overall Hilbert space “of everything” and the total Hamiltonian.

p22: As noted before, the problem of measurement cannot be even stated without a recognition of the existence of systems. Therefore, our appeal to the same assumption for its resolution is no sin. However, a compelling explanation of what are the systems — how to define them given, say, the overall Hamiltonian in some suitably large Hilbert space — would be undoubtedly most useful.

 

[Edward Wij]

Zurek and Schlosshauer do mention the factoring problem - whether it is a problem depends on what interpretation one is using.

Schlosshuaer, http://arxiv.org/abs/quant-ph/0312059
p8: Also, there exists no general criterion for how the total Hilbert space is to be divided into subsystems, while at the same time much of what is called a property of the system will depend on its correlation with other systems. This problem becomes particularly acute if one would like decoherence not only to motivate explanations for the subjective perception of classicality (as in Zurek’s “existential interpretation,” see Zurek, 1993, 1998, 2003b, and Sec. IV.C below), but moreover to allow for the definition of quasiclassical “macrofacts.” Zurek (1998, p. 1820) admits this severe conceptual difficulty: In particular, one issue which has been often taken for granted is looming big, as a foundation of the whole decoherence program. It is the question of what are the “systems” which play such a crucial role in all the discussions of the emergent classicality. (. . . ) [A] compelling explanation of what are the systems—how to define them given, say, the overall Hamiltonian in some suitably large Hilbert space—would be undoubtedly most useful.

Zurek, http://arxiv.org/abs/quant-ph/9805065
p2: We can mention two such open issues right away: Both the formulation of the measurement problem and its resolution through the appeal to decoherence require a Universe split into systems. Yet, it is far from clear how one can define systems given an overall Hilbert space “of everything” and the total Hamiltonian.

p22: As noted before, the problem of measurement cannot be even stated without a recognition of the existence of systems. Therefore, our appeal to the same assumption for its resolution is no sin. However, a compelling explanation of what are the systems — how to define them given, say, the overall Hamiltonian in some suitably large Hilbert space — would be undoubtedly most useful.

What interpretations is it a problem and what interpretations is it not a problem? I think it's not a problem with Bill Ensemble because the mere fact there is outcome is measurement problem solved for him. So let's handle the others for us who are not Ensemblers.

 

[bhobba]

What interpretations is it a problem and what interpretations is it not a problem? I think it's not a problem with Bill Ensemble because the mere fact there is outcome is measurement problem solved for him. So let's handle the others for us who are not Ensemblers.

First thanks to Atty for giving the answer.

What its a problem with and not a problem I think depends on future research.

As I have always said at present its just a possible problem - a lot more work needs to be done. Just as an example of one way out of the difficulty (assuming it is a difficulty - which I am not that sure of) is maybe systems like say the CBMR would be strongly influenced over time by the QFT vacuum but large scale macro objects like you and me would not be. That could be the natural way to factor systems. Just an idea to show it really needs a lot more investigation.

Thanks
Bill

 

[Edward Wij]

First thanks to Atty for giving the answer.

What its a problem with and not a problem I think depends on future research.

As I have always said at present its just a possible problem - a lot more work needs to be done. Just as an example of one way out of the difficulty (assuming it is a difficulty - which I am not that sure of) is maybe systems like say the CBMR would be strongly influenced over time by the QFT vacuum but large scale macro objects like you and me would not be. That could be the natural way to factor systems. Just an idea to show it really needs a lot more investigation.

Thanks
Bill

If you have a pure state. Isn't it there is no interference when considering just the subsystem.. why do you need to make separate non-interference via the randomness in the quantum vacuum? Or rather.. in a pure state, what does it mean to randomize phases.. would you still get pure state.. or would randomizing phases produce the born rule causing collapse?

 

[bhobba]

If you have a pure state. Isn't it there is no interference when considering just the subsystem.. why do you need to make separate non-interference via the randomness in the quantum vacuum? Or rather.. in a pure state, what does it mean to randomize phases.. would you still get pure state.. or would randomizing phases produce the born rule causing collapse?

Did you read the preceding chapters like I said please, please read?

When one traces over the environment intuitively the random phase relative to the phase of what's being observed scrambles it leading to an average phase of a big fat zero ie no interference terms.

As chapter 26 said:
'if the sum includes a large number of random phases, |α| can be quite small. Hence a random environment can produce decoherence even in circumstances in which a non-random environment (as discussed in Secs. 26.2 and 26.3) does not.'

But to understand that please please read the preceding chapters like I asked. It will take time and effort - but there is no short-cut.

The quantum vacuum example was just a way we get a random environment which is what Ruth has an issue with - she thinks that the random phases need an explanation - I don't - or rather believe its explained by QM and reasonable statistical reasoning. Intuitively, in the examples of photons, they will be absorbed and re-emitted many times before interacting with something. The re-emission will be random via its interaction with the quantum vacuum, hence the phases relative to what's being observed will be random. Note - this is intuitive - what is really going on is much more complex:
https://www.physicsforums.com/threads/do-photons-move-slower-in-a-solid-medium.511177/

This is why I would like someone more conversant with this stuff (ie QFT and solid state physics) to comment.

Thanks
Bill

 

[Edward Wij]

Did you read the preceding chapters like I said please, please read?

When one traces over the environment intuitively the random phase relative to the phase of what's being observed scrambles it leading to an average phase of a big fat zero ie no interference terms.

As chapter 26 said:
'if the sum includes a large number of random phases, |α| can be quite small. Hence a random environment can produce decoherence even in circumstances in which a non-random environment (as discussed in Secs. 26.2 and 26.3) does not.'

But to understand that please please read the preceding chapters like I asked. It will take time and effort - but there is no short-cut.

The quantum vacuum example was just a way we get a random environment which is what Ruth has an issue with - she thinks that the random phases need an explanation - I don't - or rather believe its explained by QM and reasonable statistical reasoning.

Thanks
Bill

I've read it. I know tracing over the environment introduces the born rule.. and I was asking if randomizing the quantum vacuum can act like tracing over the environment.

 

[bhobba]

I've read it. I know tracing over the environment introduces the born rule.. and I was asking if randomizing the quantum vacuum can act like tracing over the environment.

No.

Its an (intuitive) explanation of why the phases are random.

BTW I suggest you reread it again - tracing over the environment doesn't lead to the Born rule from that account - you may be getting confused with some stuff of Zureck.

Thanks
Bill

 

[Edward Wij]

No.

Its an (intuitive) explanation of why the phases are random.

BTW I suggest you reread it again - tracing over the environment doesn't lead to the Born rule from that account - you may be getting confused with some stuff of Zureck.

Thanks
Bill

Ok. Do you have any references about the role of spacetime in all this.. because without spacetime, there is no environment or even systems and may be involved in factoring. This would begin my quest on quantum spacetime and how to connect the two together in pondering on the measurement problems.

 

[bhobba]

Ok. Do you have any references about the role of spacetime in all this.. because without spacetime, there is no environment or even systems and may be involved in factoring. This would begin my quest on quantum spacetime and how to connect the two together in pondering on the measurement problems.

Yes - read any QFT textbook. Space-time as per Special Relativity is what its built on.

Here is a text:
https://www.amazon.com/dp/019969933X/?tag=pfamazon01-20

Be aware however is its a step above what we have been discussing here.

Added Later:
The following book examines its relation to the measurement problem:
https://books.google.com.au/books?id=tzYC0KAJot4C

Thanks
Bill

 

[Edward Wij]

Yes - read any QFT textbook. Space-time as per Special Relativity is what its built on.

Here is a text:
https://www.amazon.com/dp/019969933X/?tag=pfamazon01-20

Be aware however is its a step above what we have been discussing here.

Thanks
Bill

I've read it. But isn't it QFT is just an effective field theory. The real theory of quantum spacetime *may* have lower energy consequences not predicted by QFT which can even serve as the collapser of wave functions. Maybe have to ask this in the Beyond Standard Model forum. But then just for context. Would like to know what you think of it and whether there are references of beyond QFT along these theme.

 

[bhobba]

I've read it. But isn't it QFT is just an effective field theory.

Hmmmm. I think you are misunderstanding things in those texts because QFT is not an effective field theory - effective field theory's are examples of QFT's. We have zero evidence that the much vaunted theory of everything that lifts the veil beyond about the plank scale may not be a QFT - string theory for example is a QFT - but more general than the usual QFT in 3+1 dimensions. Although I have read string theory may be a bit different in that ordinary QM may be sufficient for its description - but I am not expert enough to say and some say QFT and string theory are the same thing.

I think it might be wise for you to more carefully study those texts, and the one by Griffiths, before I discuss it with you again.

Thanks
Bill

 

[atyy]

What interpretations is it a problem and what interpretations is it not a problem? I think it's not a problem with Bill Ensemble because the mere fact there is outcome is measurement problem solved for him. So let's handle the others for us who are not Ensemblers.

Here are my thoughts on whether factoring the universe into apparatus/system matters.

1) Bohmian Mechanics - not a problem, because the apparatus/system divide is subjective, but the outcomes are objective

2) Many-Worlds - I think it could be a problem, if we keep in mind that decoherence is never perfect, and we want MWI to explain why we see a classical world, ie. why it is unlikely for conscious observers to see a non-classical world

3) Copenhagen - not a problem, because Copenhagen admits it has a measurement problem

4) bhobba's Ensemble - I would like to have bhobba comment. I think it is a problem, because Ensemble is essentially Copenhagen, and the cut should be shiftable and subjective. If the cut if shiftable, won't any cut that is placed by decoherence be too objective?