Can Quantum Computers Validate the Many-Worlds Interpretation?

[Fra]

By the way, if you'd like to see a very different argument that arrives at the same conclusion (that it doesn't make sense to think of a wavefunction as describing the system), expressed in a way that sounds very different, check out sections 9.2-9.3 in Ballentine. I just got my copy yesterday, so I hadn't read those sections when this discussion started.

Thanks, I skimmed those sections. But as expected I do not share the reasoning outlined by the author of that book. His analysis of the problems is subject to critics I tried to convey several times. I'm not sure how to make it clearer, maybe I need to put more thought into my objection to convey it.

Relative to my perspective, he is indeed mixing the views, in order to produce his contradiction. He also seems to have an odd view of the collapse.

I also have a strong feeling that he has a strange interpretation of "description of a system". To me it's obvious that a "description of a system", is NOT a property of a system alone, it is as much a property of context of the description (ie the observer).

/Fredrik

 

[Fra]

I'm not sure if it's meaningful to continue, but since these threads all seems to have the function of comparing different views I'll add some more of my view, which I understand is one of the more "solipsist" ones represented on here at least :)

I have tried to explain why this doesn't lead to logicla contradictions - it leads to interactions, which ultimately manifests the selective pressure on evolution of observers. If you think observers is strange, just think of matter if that makes more sense.

I think I see your point now, but I still don't agree with it.

There are several points in the abstractions used by Ballentine I differ with as well, so I'm not sure where to start.

I'll start with a comments to what you said before.

Even if the "collapse" in the frog's view is only approximate, we still have two rules describing a time evolution. Think of rule 1 as describing the time evolution of every part of your body, and and rule 2 as describing the time evolution of your feet when your feet interacts with the other parts of your body.

In general about "different time evolutions".

What exactly is TIME? We can't avoid that question here.

My point is that IF there are different time evolutions, they are the expected evolution relative to different views, and the parameterization of time, in a givne view, is as I see it only a parameterisation of the expected probabilistic evolution, but where probabilistic refers to a inside constructed combinatorical system of microstructures, NOT a flat time history. The combinatorical system I envision relatp to actual subjective proper time history like a compressed datafile, relates to the raw time history data. But choice of compression algorithm is what is subject to evolution.

So it is not really a _logical contradiction_. It simply means that the two views (the two observers) will have actions that are not in line with each other. So what does this mean? In my view this means there will be interactions between the views.

The result of this interaction, which can be seen as a negotiation process, is that there will be an EMERGENT consistency between the two views (an equilibration).

From my point of view, your analysis seems to jump right into the assumption that this equilibrium must always in place. This is, from my view, a flaw in the above. I think of this consistency you seek as emergent, you think of it as a hard objective constraint.

I am NOT suggesting that inconsistent views doesn't matter, I am just saying that they are not a logical contradction, like you seems to suggest. I am suggesting that instead they imply a physical interaction between the views. This will cause a mutual negotiation between the views which could have several outcomes. One wiew could be disintegrated, or both views could be adjusted for a mutual agreement.

If it's not possible to derive rule 2 from rule 1, then rule 2 contradicts rule 1. For example, your entire body including your feet goes to France. A logical consequence of that is that your feet are in France. If rule 2 says your feet are in Finland, we have a contradiction.

It is NO inconsistency in that the state of inforamtion is such that my feet expects to goto France, and my body expects to goto Finland. Because this does not describe what WILL happen. IT only describes the conditional expectation on what will happen (in my view that is).

So long before my body actually goes to Finland, and my feet to france, the "interaction" I talk about either releases my feet from my body, or more likely, the expectations of both views are deformed along the path, making them all end up in berlin.

But what I suggest imples that the states spaces are subject to dynamics as well.

In terms of the macroscopic superposition, I could put this differently. The imagined thought experiment, staring from initial cnoditions and hypotetical time evolutions is simply *unlikely* to proceed to it's final state. It suggest that the macroscopic superposition, while logically possible, is excessively unlikely, that is why we don't see this. the reason would be that it would be hard to keep information leaking out via the ne

Anyway, I think focus of Ballentine is not constructive. I do not see how this view will help solve the real problems, such as quantum gravity. In my view the motivation for the interpretational issues is that it appears naturally when you ponder what a measurement theory would be like in a more general context, where you simply don't have the massive references of classical observes OR science labs where you can repeath the same experiment as many times as you like. This circumstances are not around in the general case.

One problem is instead what the heck the physical basis of probability and this ensemble really is (I try to adress this; ballentine uses it, as it if was obvious), when it should be (to me at least) obvious why the simple frequentists interpretation doesn't work. Also a simple bayesian probabiltiy is also problematic since it uses a birds view of sample space to construct the conditional probabilities. Instead I think the formalism must be emergent from an incomplete inside view.

Most issues can be seem already in the premises. Hilbert spaces and hamiltonian time evolutions are not innocent starting points. That is a massive baggage. I think the best way to see my objections is via a black box argument.

If you have a black box, and want to learn to predict it, because the black box competes with you (takes your coffe in the morning for example). One can not just pull out of nowhere and internal structure an hilbert space of this black box. This is for you to infere. The only way to start is your interface to the box. But you don't have a definite communication channel, you just see one end of the channel, and have no clue what's on the other end.

Also picture that during this inference, the box keeps changing. So you never ever get enough statistics to justify the standard statistical reasoning. You somehow need a new strategy.

/Fredrik

 

[ueit]

Ok, now I see what you mean. I thought the basic meaning of observer was clear but may not. I'm sorry.

I'll note that I don't yet have a complete theory, I am working and looking for a reconstruction of current models. But some starting points and design principles are in place.

Roughly my view is like this.

About observers, to avoid confusion I'll note that there are two views of that.

* The inside view

- is the view of the universe an inside observer has.
This VIEW defines the observer.

analogies:

1. It's like the distinction between the self, and non-self. But this is difficult because since the observer is not static, this boundary is fuzzy and evolving.

2. Another interesting analogy is like the distinction between what you know FOR SURE and what you are only guessing. I'm sure you would agree that there is a fuzzy boundary here, in particular where you are "almost sure" but not quite. Or you can argue that you are never sure and it's all about various degrees of certainty - this view matches in my view as well.

Since I'm picturing a reconstruction I avoid using too much standard QM terminology since people would tend to think I in an unreserved way refers to existing concetps.

But loosely speaking, I think the hilbert space is part of the observers identity. And I am not talking about the hilbert space of the environment in a decomposition H_univers = H_observer x H_remainder, I'm suggesting that math makes no sense because it mixes inside view and birds views in an IMHO conceptually illegal way.

So the hilbert space of the universe, as seen from the inside observer, is CONSTRAINED by the complexity of the observer. A simple observer can not relate to the full complexity of it's environment.

So from the inside view, I call the home of the information and state vectors as a system of microstructures. And this can not be questioned objectively by the inside observer. It just is. However, as to the question how it became to me, then there is an evolutionary picture in which this microstructure evolves and can gain complexity (which I associate also to mass in some form)

The "problem" for the inside view, is to survive the challange of the environment. In this picture, what was usually called an inconsistency between views, is here instead just exactly what causes the evolution (both time an large perspective)

* external view

This is the view, where ONE observer ponders that parts of this own environment can be thought of as separate observers that are mutually interacting. IE. One observer observes other observers.

In this view, the notion of observer is farily unclear. But my point is that this is not a big problem. It is only a problem for those who can't let go of some realist ideals.

I am sory, but I'm not closer to understanding what an observer means in your theory. In a previous post you said that an observer could be an atom for example. Then I have asked you if you have redifined "observer" to mean any system or not. So, I will repeat the question. Do you call "observer" any particle/group of particles? Does an entangled pair of photons qualify as "observer"? Give me some clues about the properties an observer should have so I can understand how this theory is going to be applied to experimental data. I have no clue for example what "an inside view" of an atom is supposed to be and in what sense we can say an atom has something of this sort.

This is an example of a very general an repeating problem. It also comes in other disguises.

It's the origin problem.

I didn't say I think there is no law, whatn I mean is that IN GENERAL there is no objective law which we can be sure all observers agree upon.

Instead, I am suggesting that objective LAW is emergent.

There are predictions, but they only live in an evolving context, so even faulty prediction has a place. The observer which embodies consistently flawed predictions, will have his microstructure destroyed and deformed by environmental feedback.

So in an near equilibrium scenario, there are fapp type of objective laws, and we recover pretty much the standard physics, but what I am suggesting is a possible way to in a deeper way understand why the laws of physics are like they are, and wether they are better seen as evolving or fixed.

I'm suggesting that you can LEARN and improve, without having fixed rules for learning, because whole point is that you do not only learn as per fixed rules, you even learn the learning rules. The context is evolution.

The evolutionary context is IMO the best way to see law. Wether these observed laws are the same as some "real laws" is something to which nature is indifferent.

Because you have an analogy with the theory of evolution I want to point some of the necessary preconditions for such an evolution to take place.

There is certainly something that changes (that's why we call it "evolution"), and this "something" is the molecular structure of DNA. This in turn changes the chances of survival/multiplication of the "DNA owner" and those structures that are successful remain, the other disappear. The life-forms are able to learn to some degree, depending of their brain.

I don't think that evolution would be possible if the laws themselves (as opposed to a certain molecular configuration) would change. How could an animal adapt to an ever-changing environment, how could the selection lead to an improvement if, say, the chemistry of DNA would change over time? A successful DNA today will be crap tomorrow. The "rules" of the game must be stable, at least for the period of time evolution is supposed to take place. Those rules are, IMHO, required for every theory to make sense and be useful at all. Do you have such laws in your theory?

You say the the laws are emergent, however, I don't see how from an absence of any law at fundamental level anything other than statistical noise could emerge.

 

[Fredrik]

Fra, you are no longer talking about quantum mechanics. You see that, right? It's enough to deny one of the axioms of QM to make sure that what we're talking about isn't QM, and you're denying both of the time evolution axioms. (Yes, to say that they define the start of a negotation is to say that they are false).

I haven't been able to make sense of what you're saying about the observers' expectations, so I can only say that I hope you understand that if a "theory" makes two different predictions about the result of the same experiment, then it isn't really a theory.

 

[Fra]

Fra, you are no longer talking about quantum mechanics. You see that, right?

Yes definitely. In my first post in this thread I said

"My view is more than interpretations, it suggest a reformulation of QM, where QM is emergent."

This does if you read it as intendend not contradict most of the predictions of quantum mechanics and QFT we know is successful (that would be foolish and ignorant, but I'm not doing that). Instead, I have an explanation for this (it's emergent), but in a more general setting, and I think QG is one such domain,

But yes I don't quantum mechanics, as it stands as an acceptable foundation that should be kept unquestioning when pondering about some of the open problems in physics.

That's my "interpretation of QM". I don't see that it's worse than any other :)

I can only say that I hope you understand that if a "theory" makes two different predictions about the result of the same experiment, then it isn't really a theory.

Correct. But I am trying to advocate a more delicate view of theory. It's clear that I fail to convey it. But then, this is why I am still working on this. I need to make a lot more progress and tune the arguments. This is why I call this my interpretation, but it really is an ambitious attempt of reconstructing a measurement theory.

/Fredrik

 

[Fra]

I tried to reply with some background motivation, since I think a simple answer can be misinterpreted. But I'll try to give more compact answers.

I am sory, but I'm not closer to understanding what an observer means in your theory. In a previous post you said that an observer could be an atom for example. Then I have asked you if you have redifined "observer" to mean any system or not. So, I will repeat the question. Do you call "observer" any particle/group of particles? Does an entangled pair of photons qualify as "observer"?

Yes, and subsystem of the universe can be an observer; observing the rest.

But the most important thing is that the inside and the external pictures are different. This is why the external picture of an observer is never exact or static. It is generally always subject to uncertainty. But not the simply type of uncertainty in the sense of a state vector beeing smeared out of a part of a state space. It's more dramatic, because the state space itself is also uncertain.

As to the obvious question. Why not just replace this silly hierarchy of spaces of spaces of spaces with a larger master state space? Well, because a finite observer can not RELATE to such complexity.

Another problem with that view, is that it leads to a terrible initial value problem. In my view the initial value problem goes away because from the inside view, the state spaces are inflating.

I understand that this is unclear if you are coming from a different perspective.

However, just because any subsystem sort of qualifies as a potential observer, doesn't mean that each subsystem is distinguishable as a coherent system from a given view.

If you think I'm just reinventing words here, then I think I missed to convey several points. But I'll leave this as is.

I have no clue for example what "an inside view" of an atom is supposed to be and in what sense we can say an atom has something of this sort.

Give that none of what I tried to convey, and I admit it's strange and radical, seems to make sense to anyone on here, except possibly a few of the philosophers on here, I am not sure if I can explain this at the moment.

It's fairly clear to me, but it's not yet at the state of a complete theory, it's only fragments I'm still struggling to put together. Fortunatlely and oddly I have a strong confidence in this idea.

But the clues is this:

One "assumption" if you wish to call it that, is that each observer can only hold finite information. This also means any subsystme of the universe can only hold finite info.

This, incombination with all other things I tried to convey with actions and information states, implies that the information capacity of an observer, constraints the complexity and variety of it's interactions.

In particular do I envision that the IMAGE of the remainder of the universe, is constrained to a finite "screen". The degrees of freedom of this screen, is related to the observers complexity.

Anyway, the actions can be built combinatorically from the discrete observer structure.

But ontop of this, things get worse. The degrees of freedom is not fixed. An observer, can "conquer" or come to take control of degrees of freedom in it's environment, and thus "grow" it's own complexity. The revserve process of loosing degrees of freedom also is possible.

This latter thing is in my view closely related to the origin of inertia and mass, and also gravity-like pheonmena emerges in this view, because the degrees of freedom in the environment self-organise and form a web of interconnected communicating systems. this should also explain properties of spcaetime.

In this picture gravity is ultimately originating from two "inertial systems" that are remotely communicating, the result of this is that the two systems are slowly getting closer. The the distance measures is related to information geometric measures.

All these things are related in my view. This is why I really see this as a proper reconstruction, because I do not start with 4D spacetime. I do not start with the known forces.

I start with an abstract concept of communicating structures, and tries to convey to the exten possible at this ummature level, how interactions (laws, symmetrues) are emergent.

This may seems like giving an infinite possibilities, but I think not. The fact that all systems are finite, and if you start the evolution at minimum complexity. The possible structures and also interactions are strongly limited. In fact unification of interactions are a must. Because there is no complexity around to distinguish diversity of interactions. there is only one force.

You say the the laws are emergent, however, I don't see how from an absence of any law at fundamental level anything other than statistical noise could emerge.

I do.

See above. The major trick is the assumption of finite information capacity. I'm sorry but it's apparently hard to describe the idea for some reason. Self organisation and selection should make sure that a large complexity with only uniform noise is very unlikely. Self.organisation and emergence of structure and law in fact stabilises the universe.

This is not longer QM. But like I mentioned, I think that eventually we will understand why the QM structures is the way it is, but in order to do that I think we need to see the entire picture. IE. all interactions, space, time and matter.

/Fredrik

 

[Fra]

I hope no one thinks that the idea of finite information capacity suggests the universe is like a game of life, then one has missed the inside vs external view thing. the degrees of freedom in the universe can not be described in a diff invariant or observer invariant way. It's more complicated. The complication arises because any statement of the universe relate to an inside view. There is no true gods view or birds view in my vision.

I agree that it's qualified headache to make sense out of this. But I think of hte suggestions of the visions as probably facts about nature, without trying to simplify. It's my problem to make sense out of it. I can not hide for complications just because they seem inconsistent. More probably something is wrong with my understanding.

/Fredrik

 

[Fredrik]

The finite information capacity is already a prediction of several different partially successful attempts to combine QM and GR. The maximum information that can be stored in a region of space is proportional to the surface area of the boundary of that region. Intuitively, it should be proportional to the volume, but it isn't. Think about making a stack of RAM memory cards for example. At first the information content grows as the volume of the stack, but eventually the stack would collapse to a black hole. Now the area of the event horizon is proportional to the amount of information that has fallen into it.

 

[Fra]

The finite information capacity is already a prediction of several different partially successful attempts to combine QM and GR. The maximum information that can be stored in a region of space is proportional to the surface area of the boundary of that region.

Yes, and what I describe is related to this. But so far there is no IMHO fully satisfactory model that implements all these things. There are several research programs and I have tried to skim what others have done and I share fragments of ideas from a number of people working on different ideas:

- C. Rovelli (the orginal reasoing begind relational QM is good, but not the finish)
- Smolin(evolving law and CNS)
- Ariel Caticha(physical law as rules of inference; he tries to "derive" General relativity from the rules of inference, applied to physical systems rather than human brains)
- Olaf Dreyer(internal relativity; relating to the "inside view" I talk about)
- Zurek(what the observer knows, is inseparable from what the observer IS; however I don't fully belong to Zureks decoherence camp, in my view that's aprt of the story not all of it.) etc.
- Penrose also has some interesting thoughts on combinatorical approaches, but he is too much of a realist for my taste.

Try to find some common denominators above, and it's getting closer to what I'm talking about.

/Fredrik

 

[Fra]

Needless to say the mathematical model of this is still in progress but there are several ways to associate results from some of the semi-classical QG results with the ideas I envision, that might provide a angle that makes the crazy stuff more appealing.

One this is the randomness of black hole radiation, and the problem of informationloss. In my picture, I expect that eventually the black hole radation contains no information, from the point of view of the black hole (here the black hole takes the role of the observer). However, it can still contain information relative to an outside observer. It has to do with relative complexity.

A simple observer, can not decode the information from a sufficiently complex source, so this means it contains no information. It's observer to be just noise.

It would also be in line with that a small black hole, would radiate in a "less random" faishon as judged from an outside observer. the information content in the radiation is not a property of the radiation itself, it depends on the observer.

In particularly interesting would be to ponder about the exact interaction pattern and stability of very small black holes. Quite possible, these would, if they are stable by some yet unknown quantum rules (just like Quantum theory explains the stability of atoms) would not actually be perceived as black holes to a large outside observer, but rather as particles. It's not totally impossible that the subatomic forces are quantum versions of blach hole interactions. The point would be that the continuum approxiation from GR first of all would be totally invalid. Most probalby there are no physical singularities. but all this no one knows, all we have now are various different semi-classical attempts to probe this domain.

/Fredrik