Copenhagen: Measured or Observed?

[Dmitry67]

I don’t like CI. But I was always thinking that CI is an idealistic interpretation, based on the consciousness and the existence of intelligent observers.

In Bohr’s time it was simple. He believed in a sharp line between quantum world and macroscopic world. Quantum event Q was registered by the Measurement device M et voila: wavefunction collapse.

Q -> M

But we know how tiny the measurement devices can be. On the other hand, we can put millions of particles into entangles state. So, what happens when we store a result of a quantum event in some tiny qbit measurement device? Why it does not collapse?

Q -> M1

CI proponents say: well, storing Q in M1 is NOT a measurement. Only then, when we observe status of M1 we perform a measurement:

Q -> M1 -> M2

Now we have 2 devices: small M1 and a bigger one: M2. But wait, we can make this chain of measurement devices much longer, making a ‘consequent measurement’

Q -> M1 -> M2 -> M3 -> … => Mn

So what measurement is ‘real’? There are only 2 options:
1. CI is not about the measurement. It is about the observation. CI is idealistic and it requires a consciousness C to collapse a wavefunction:

Q -> M1 -> M2 -> M3 -> … => Mn -> C

2. CI must give an exact definition of what Mi *IS* a measurement device. Knowing that measurement devices can be tiny and consist of few atoms, CI must give a detailed explanation of what combinations of atoms are measurement devices and what combinations are not measurement devices (and clearly it can’t do it)

So why CI talks about measurement while “wavefunction is not real, it is just an information” which clearly suggests the consciousness as an only collapse agent. So instead of thinking about the superstrings about the most fundamental things, we should think about the consciousness as something irreducible to simpler things.

It makes some sense, but it is definitely not the way how CI proponents see that interpretation.

 

[kote]

So why CI talks about measurement while “wavefunction is not real, it is just an information” which clearly suggests the consciousness as an only collapse agent. So instead of thinking about the superstrings about the most fundamental things, we should think about the consciousness as something irreducible to simpler things.

It makes some sense, but it is definitely not the way how CI proponents see that interpretation.

Bohr:

“It lies in the nature of physical observation, nevertheless, that all experience must ultimately be expressed in terms of classical concepts, neglecting the quantum of action.”​

Bohr doesn't talk much about measurement devices. The primacy of classical properties is more due to a failure of the human understanding than anything ontological. Physics is about epistemology. It's about knowledge. Our knowledge is limited to classical concepts.

"A close connection exists between the failure of our forms of perception, which is founded on the impossibility of a strict separation of phenomena and means of observation, and the general limits of man’s capacity to create concepts, which have their roots in our differentiation between subject and object.”​

It is also a failure of our understanding that we necessarily view things as being objective, ignoring the fact that they are necessarily context dependent. His answer:

"For describing our mental activity, we require, on one hand, an objectively given content to be placed in opposition to a perceiving subject, while, on the other hand, as is already implied in such an assertion, no sharp separation between object and subject can be maintained, since the perceiving subject also belongs to our mental content. From these circumstances follows not only the relative meaning of every concept, or rather every word, the meaning depending upon our arbitrary choice of view point, but also that we must, in general, be prepared to accept the fact that a complete elucidation of one and the same object may require diverse points of view which defy a unique description."​

QM isn't even the game changer for Bohr, relativity is.

“The theory of relativity reminds us of the subjective … character of all physical phenomena, a character which depends essentially upon the state of motion of the observer.”

“[Quantum mechanics] may be regarded as a natural generalization of the classical mechanics with which in beauty and self-consistency it may well be compared. This goal has not been attained, still, without a renunciation of the causal space-time mode of description that characterizes the classical physical theories which have experienced such a profound clarification through the theory of relativity.”​

He also thanks Einstein “with respect to our emancipation from the demand for visualization.”

For Bohr, QM isn't about measurement devices and it isn't about collapse. Take classical entities and call them real (macroscopic realism - the chair is real, particles are real). Add relativity and QM to show that our classical view of causation is wrong, and you are forced to throw out the causal implications of having real, persistent, classical entities. You can't understand what causes the classical events we see; you can't visualize anything beneath the classical level.

It would be a mistake to say that Bohr placed any emphasis on consciousness though.

“We are here so far removed from a causal description that an atom in a stationary state may in general even be said to possesses a free choice between various possible transitions to other stationary states.”​

Even atoms can have free will. Furthermore, the appearance of consciousness is simply an irreducible phenomenon dually and inconsistently describing the world in the same way that wave-particle duality appears. It is a failure of our understanding that we necessarily can't reduce the two concepts to something more basic, but must inconsistently consider each to be basic.

"When considering the contrast between the feeling of free will, which governs the psychic life, and the apparently uninterrupted causal chain of the accompanying physiological processes, the thought has, indeed, not eluded philosophers that we may be concerned here with an unvisualizable relation of complementarity."​

Measurement, for Bohr, is simply the manifestation of classical properties, which can't exist persistently due to their falsified causal implications, but which must exist necessarily as the basic elements of our reality due to the epistemological limits of our conceptions/perceptions/visualizations.

There is no objective collapse. The wave function doesn't represent anything real. Observation plays no physical role.

"We meet here in a new light the old truth that in our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, so far as it is possible, relations between the manifold and aspects of our experience."​

Physics is about human knowledge and understanding, nothing more.

Jan Faye has a good description of CI at http://plato.stanford.edu/entries/qm-copenhagen. Also, sorry for the long read. It's all from a chapter in my thesis, so I had all these quotes. I'll spare you the rest though . I hope it's helpful in clearing up some of the collapse garbage out there.

 

[alexepascual]

So what measurement is ‘real’? There are only 2 options:
1. CI is not about the measurement. It is about the observation. CI is idealistic and it requires a consciousness C to collapse a wavefunction:

Q -> M1 -> M2 -> M3 -> … => Mn -> C

2. CI must give an exact definition of what Mi *IS* a measurement device. Knowing that measurement devices can be tiny and consist of few atoms, CI must give a detailed explanation of what combinations of atoms are measurement devices and what combinations are not measurement devices (and clearly it can’t do it)

So why CI talks about measurement while “wavefunction is not real, it is just an information” which clearly suggests the consciousness as an only collapse agent. So instead of thinking about the superstrings about the most fundamental things, we should think about the consciousness as something irreducible to simpler things.

It makes some sense, but it is definitely not the way how CI proponents see that interpretation.

I don't like CI either. But I think you may be thinking about one of many different flavors of the CI. Von Neumman, Wigner?
The decoherence program is usually considered to be just a mathematical fomalism which does not imply any interpretation. I am not too sure about that. But nevertheles, you can analyze environment-induced decoherence from both the CI and MWI.
In the CI, if you consider decoherence as what causes "collapse" then you are not necessarily involving the brain in the collapse process.
CI also considers a macroscopic apparatus to be an observer and often considers collapse as happening during interaction with the first macroscopic apparatus.
Now, the decoherence theory should be able to explain how the interaction of a single particle in a superposition with something that is composed of a large number of atoms brings about collapse. I haven't seen any convincing explanation of how the decoherence theory does that. But maybe I have not read the right articles.
I posted a question some time ago that nobody answered: If a quantum system interacts with an apparatus, before interaction the composite system may be described by the vector product of the individual Hilbert spaces. There are no correlations and all different combinations of the individual components of each system are present. When the particle gets entangled with the apparatus, each etate of the particle gets linked to one particular "pointer state" of the apparatus. So it looks like now the realm of possibilities is restricted to a smaller Hilbert space where some combinations are not allowed anymore. It is claimed in many places (Including in Everett's paper) that this process, (also called pre-measurement) represents a unitary transformation. I can't understand how something that reduces the size of the Hilbert space can be unitary. Maybe I am missing something.
In Everett's paper, he considers a Hamiltonian acting for a fixed time. This seems like a trick that would not normally be done in nature. How does the hamiltonian how long to act? It seems to me that to get these correlations you should have a damping constat and an irreversible process, where you see overall increase in entropy.
Then you have the problem of which of the different eigenstates to choose. I don't see an easy way to explain that outside of the MWI.

 

[Dmitry67]

It would be a mistake to say that Bohr placed any emphasis on consciousness though.

Furthermore, the appearance of consciousness is simply an irreducible phenomenon dually and inconsistently describing the world in the same way that wave-particle duality appears.

The statements above are inconsistent.
If consciousness is irreductable then it is a fundamental notion (that you for confirming it in CI), like may be spacetime, universe etc.
But then Bohr made a mistake by not placing any emphasis on that.

 

[Dmitry67]

alexepascual, before we even start talking about the decoherence: CI had only one "collapse agent": measurement. It was long before the discovery of decoherence. So the decoherence is something CI really does not want, it is an alternative explanation of the same thing. After all that blah-blah-blah stuff explaining the collapse if appeared that no collapse was needed at all to explain what we see! it is the strongest argument against CI!

 

[kote]

The statements above are inconsistent.
If consciousness is irreductable then it is a fundamental notion (that you for confirming it in CI), like may be spacetime, universe etc.
But then Bohr made a mistake by not placing any emphasis on that.

Consciousness as something objective or ontological is not something proposed by Bohr. What is basic is epistemological human knowledge. There is a subtle difference. As being necessary to human knowledge, Bohr also thought that space-time and classical properties were necessarily basic. His thoughts here were very similar to Kant's categories of perception.

Also, the appearance of consciousness does not in any way interfere with a complementary physical description of events.

 

[Dmitry67]

kote, so do you think that consciousness is a fundamental irreductable notion or not?

 

[kote]

kote, so do you think that consciousness is a fundamental irreductable notion or not?

Personally, no, but that's another thread. Bohr, however, barely ever talked about consciousness. I've quoted about the only times I could find where he discussed the issues. Consciousness was just not part of physics for Bohr. Knowledge, on the other hand, was very basic for him. The titles of his books are "Atomic Theory and the Description of Nature" and a few collections of essays on "Atomic Physics and Human Knowledge."

From Jan Faye on SEP:

Bohr therefore believed that what gives us the possibility of talking about an object and an objectively existing reality is the application of those necessary concepts, and that the physical equivalents of “space,” “time,” “causation,” and “continuity” were the concepts “position,” “time,” “momentum,” and “energy,” which he referred to as the classical concepts. He also believed that the above basic concepts exist already as preconditions of unambiguous and meaningful communication, built in as rules of our ordinary language.​

Consciousness is not a part of Bohr's philosophy. Neither are observers. It's all about knowledge and real classical properties and objects.

 

[Fredrik]

1. CI is not about the measurement. It is about the observation. CI is idealistic and it requires a consciousness C to collapse a wavefunction:
...
So instead of thinking about the superstrings about the most fundamental things, we should think about the consciousness as something irreducible to simpler things.

This is just crazy talk, but maybe that was your point?

2. CI must give an exact definition of what Mi *IS* a measurement device.

It isn't possible to define measurement devices exactly. This is a problem for all scientific theories. Take SR for example. Minkowski space is a beautiful mathematical model, but it's not a theory. One of the axioms that define SR says that a clock measures the proper time of the curve in spacetime that represents its motion...but a clock isn't defined by the theory. It can only be defined intuitively. This is a limitation of science, not of the CI.

CI must give a detailed explanation of what combinations of atoms are measurement devices and what combinations are not measurement devices (and clearly it can’t do it)

It can't give you the kind of detailed explanation you want, because it isn't possible to define the measurement devices in that kind of detail, but if you're familiar with decoherence (which is a phenomenon that can be studied in the framework of the CI), you already know a good definition of a measurement. It's an interaction between the system and its environment that entangles the eigenstates of one of the system's observables with macroscopically distinguishable states of a system that for all practical purposes can be treated as classical. (So qubits won't do).

 

[Dmitry67]

1 This is just crazy talk, but maybe that was your point?

2
It isn't possible to define measurement devices exactly. This is a problem for all scientific theories. Take SR for example. Minkowski space is a beautiful mathematical model, but it's not a theory. One of the axioms that define SR says that a clock measures the proper time of the curve in spacetime that represents its motion...but a clock isn't defined by the theory. It can only be defined intuitively. This is a limitation of science, not of the CI.

3
It can't give you the kind of detailed explanation you want, because it isn't possible to define the measurement devices in that kind of detail, but if you're familiar with decoherence (which is a phenomenon that can be studied in the framework of the CI), you already know a good definition of a measurement. It's an interaction between the system and its environment that entangles the eigenstates of one of the system's observables with macroscopically distinguishable states of a system that for all practical purposes can be treated as classical. (So qubits won't do).

1 Yes, I believe it is close to Fra's point of view.
I can accept it as an option even I don't like it
But for CI proponents it is not fair to switch from completely idealistic "it is just a knowledge" point of view to an objective point of view. If it is just a knowwledge - then everything is just a knowledge, just a shadow in our consciousness.

2 Well, TOE should be word "baggage" free. Just formulas.

3 No, no, don't try to save CI! :) In CI Decoherence DOES NOT replace collapse! No, no, and no! jambaugh (the very last CI proponent here) had confirmed it explicitly: there is Decoherence and there is collapse. 2 different things!

 

[Fredrik]

So the decoherence is something CI really does not want, it is an alternative explanation of the same thing.

This is completely wrong. Decoherence is a physical phenomenon that doesn't in any way contradict a "Copenahagenish" formulation of QM. In fact, it can be derived from its axioms.

What decoherence has added to QM is a definition of a what a measurement is. This solves some of the problems that were confusing in the past, e.g. the Wigner's friend scenario: Wigner performs a Schrödinger's cat experiment, and his friend walks in and asks him about the result. Is the question a measurement? The answer is that it's not, because the interaction that entangled the eigenstates of the observable with the macroscopically distinguishable states of the "almost classical" system has occurred before the friend walked in.

 

[Dmitry67]

Consciousness is not a part of Bohr's philosophy. Neither are observers. It's all about knowledge and real classical properties and objects.

Well, we can't speculate on how Bohr would change his mind when he learned about the microscopic "measurement" devices.

So even if Bohr never talked about the consciousness, what do you think? Or, what is a CURRENT flavor of the CI?

 

[kote]

It can't give you the kind of detailed explanation you want, because it isn't possible to define the measurement devices in that kind of detail, but if you're familiar with decoherence (which is a phenomenon that can be studied in the framework of the CI), you already know a good definition of a measurement. It's an interaction between the system and its environment that entangles the eigenstates of one of the system's observables with macroscopically distinguishable states of a system that for all practical purposes can be treated as classical. (So qubits won't do).

What Fredrik said... Also, Bohr gives clues that he feels the same way about measurement later in life as he clarifies his language to try to avoid some of the confusion. From Faye again:

Bohr no longer mentioned descriptions as being complementary, but rather phenomena or information. He introduced the definition of a “phenomenon” as requiring a complete description of the entire experimental arrangement, and he took a phenomenon to be a measurement of the values of either kinematic or dynamic properties.​

A measurement is the result you get from producing a phenomenon by arranging a system such that it manifests classical properties.

Similarly he stopped talking about uncertainty. The emphasis was that there is no phenomenon and there are no uncertain hidden variables when objects aren't interacting classically. Classical properties, while real, only exist during measurement/manifestation/interaction.

A measurement is a classical output from a system.

 

[Dmitry67]

This is completely wrong. Decoherence is a physical phenomenon that doesn't in any way contradict a "Copenahagenish" formulation of QM. In fact, it can be derived from its axioms.

Sorry, my post was not clear.

You are correct, it does not contradicts on the formal level. But agree with me, the whole motivation for inventing the collapse thing was to explain the macroscopic behavior, which was not able to be derived directly from QM at Bohr's time. After the discovery of the Decoherence the reason for inventing the collapse had completely dissapeared! And CI ended with 2 things to explain the same.

 

[Dmitry67]

A measurement is a classical output from a system.

No, no!
See my very first post!

Classical output = no superposition of states = collapsed to a definite outcome = measured

Classical is measured, and to be measured is to get a classical outcome.


You see, I am fighting here against the hidden recursive definitions which are almost everywhere!

 

[kote]

Well, we can't speculate on how Bohr would change his mind when he learned about the microscopic "measurement" devices.

So even if Bohr never talked about the consciousness, what do you think? Or, what is a CURRENT flavor of the CI?

I can't think of any developments that would challenge Bohr's original views. He was very aware of Schrodinger's cat and he didn't think anything special about measurement that is inconsistent with current views. Any inconsistency would simply be semantics and Bohr would stick with his own original definitions or tell you how to make things work out linguistically.

The whole notion of "collapse" was not an issue for Bohr and was not anything he ever talked about or would need to talk about. Bohr never considered the formalism to be real. Classical objects were always real and basic for Bohr. The wave function represents the probability that when we look in the box we'll see a dead cat.

 

[kote]

No, no!
See my very first post!

Classical output = no superposition of states = collapsed to a definite outcome = measured

Classical is measured, and to be measured is to get a classical outcome.You see, I am fighting here against the hidden recursive definitions which are almost everywhere!

It's a tautology not a recursion . Unmarried man = bachelor. Superpositions of states are not real. There is nothing else that needs to be explained.

The problem with CI that I see is that theoretically we can't explain why we see the results we do at any deeper level. We will never do any better than the current theory. If you can accept that we may be at the limits of our knowledge, then CI works out beautifully. There are no collapse issues and we get macroscopic and microscopic entity realism (as opposed to theory realism). The question is just, which pill is easier to swallow? The one required by CI or the ones required by other interpretations? Edit: As for switching between knowledge and objectivity... the wave function is about incomplete knowledge (no theory realism) but classical objects are objectively real (entity realism).

I'll add that Bohr would define classical properties not by what is measured, but by preexisting and necessary notions of classical concepts per my previous post. Measurements are always classical, yes, but classical properties can be defined without measurement. They are innate and a priori and are a necessary part of human understanding.

From SEP's description of Kant's categories:

Although these are categories of the understanding, they nonetheless retain a certain sort of ontological import, as it is a priori that they apply universally to all objects of possible cognition (A79/B105). In this way, by delineating the concepts that are a priori necessary for the cognition of objects, we can acquire knowledge of categories governing any possible object of cognition, and so acquire a sort of descriptive set of ontological categories, though these must be understood explicitly as categories of objects of possible cognition, not of the thing in itself.

http://plato.stanford.edu/entries/categories/#KanCon​

 

[Fra]

1 Yes, I believe it is close to Fra's point of view.
I can accept it as an option even I don't like it
But for CI proponents it is not fair to switch from completely idealistic "it is just a knowledge" point of view to an objective point of view. If it is just a knowwledge - then everything is just a knowledge, just a shadow in our consciousness.

I am not sure what's close to my view? I don't quote recognize myself in the preceeding.

The need for consioussness or intelligence sounds like the repeated association that QM would have anything to do with the human brain, and the QM is a phenomenon of the human brain. That is definitely not what I think, I think I tried to make that point several times.

From what I remember about your reasoning, you have a much stronger realist view that I do. This is the root of our disagreement. So I somehow see why you have a difficulty to appreciate my reasoning, and from your point of view, my reasoing appears circular - right? Am I right? :)

I replace in my interpretation Bohr's classical reference with the inside perspective in that sense that instead of thinking of the references as a fix objectivity, I see it as a rational calculated basis for the action, as part of a game. The action of a system, observing a second system, is as if the first system's view of the second is correct and objective, while in fact all the difference it makes is to provide a basis for the action. But this "basis" is deformning or updating throughout the interaction.

The circularity you see, is the time evolution. On each iteration there is progress. If you want, I view TIME as an inference process, but due to the inertia inferences are not immediate. The time evolution takes place as I see it at several hierarchial levels, the most vibrant level is the ordinary time evolutiom, the slowest level correspond to the evolution of physical law.

So if you see my view as a "clean interpretation", it is correct that it doesn't make sense. But if you take it even more seriously, it suggest how to improve QM - that is how I see it.

So, I would say that my view does not make sense if you insist that the QM formalism as we know it is fundamentally correct without expcetion at alla scales. If you think however, that QG requires a modificaton of QM, THEN I think it does make sense.

This is why I reserved myself several times in this interpretational discussions that I don't see my view as a clean interpretation. Among the plain interpretations though, CI or something like Bohrs original reasoning is what I find the most sensible.

But my preferred view goes beyond that.

/Fredrik

 

[Fra]

You see, I am fighting here against the hidden recursive definitions which are almost everywhere!

I speak only for my own view and in my view, there is self-reference, this is correct.

But this is not a problem. You seek a timeless static conclusion. For me, the indication is instead that such static timeless characterisation of physics does not exist.

There is a problem of time buried in this discussion. If you look around, the universe isn't static, what is the basis for expecting static conclusions?

Again I see here a clear preference to your view if you have a realist view of physical law. I think difference explains most of our differences in reasoning.

/Fredrik

 

[Fra]

There is a problem of time buried in this discussion. If you look around, the universe isn't static, what is the basis for expecting static conclusions?

As an historical analyg, perhaps one can ask what was Einstein's reason to insist on a static universe?
http://en.wikipedia.org/wiki/Static_universe

Eventually, it after all seemed like the universe isn't static.

In any learning process, knowledge is never static. I see no good reason why a inferrable physical law should be static or timeless. Sure, physical law is by construction somehow "timeless" but only when the time refers to a limited history, and the in that sense "timeless" law is itself evolving.

I think your main objection is the circularity here, but does it seem totally unreasonable to you, that this self-reference rather than a problem is a key to understanding something we yet don't?

/Fredrik

 

[Fra]

In a certain sense you can also say that Einsteins equation are circular, but that's the whole reason why there is an evolution of the universe, but the evolution is slow relative to the ordinary dynamics within spacetime. Here we also have a hierarchy of evolutions, from slow(almost static! no one will blame Einstein for the hunch) to fast.

As Wheeler put it
"Matter tells spacetime how to curve. Spacetime tells matter how to move"

(forgive me if the quote isn't exactly word by word as he put it, I just recalled this, but don't have hte original source)

The circularity here is not a problem, it's a key.

/Fredrik

 

[atyy]

How's this derivation of the CI?

Zurek, http://arxiv.org/abs/0707.2832 : "Finally, we point out that monitoring of the system by the environment (process responsible for decoherence) will typically leave behind multiple copies of its pointer states. Only states that can survive decoherence can produce information theoretic progeny in this manner."

 

[Fra]

How's this derivation of the CI?

Zurek, http://arxiv.org/abs/0707.2832 : "Finally, we point out that monitoring of the system by the environment (process responsible for decoherence) will typically leave behind multiple copies of its pointer states. Only states that can survive decoherence can produce information theoretic progeny in this manner."

I personally think that there are very good traits in Zureks reasoning, I like him. But as an overall opinion he does not address all the points I think should be addressed. So although I really like the spirit of some things he say, that does not satisfy me at least.

I'll try to elaborate what I like, and what I don't like later.

/Fredrik

 

[Dmitry67]

From what I remember about your reasoning, you have a much stronger realist view that I do. This is the root of our disagreement. So I somehow see why you have a difficulty to appreciate my reasoning, and from your point of view, my reasoing appears circular - right? Am I right? :)

Yes, I don't understand your view completely, but I know it is much more subjective and observer-dependent then mine, that is why I had mentioned it.

 

[Dmitry67]

I would like to know your opinions about the role of consciousness in CI. Specifically, if it is irreducible and fundamental, or if it can be derived (at least in principle) from the behavior of the molecules, cells et cetera

Why it is important in a context of CI?

If consciousness IS reducible to the simpler motions then KNOWLEDGE is nothing more than a STATE of a system. Hence, the CI description “collapse of the (unreal) wavefunction changes our knowledge about it” should be interpreted as “quantum event, amplified by some device, changes the state of some system”. The second description is biology-free, consciousness-free and 100% physical. But in that case CI *SHOULD* describe what the hell the measurement device is in terms of the configuration of atoms.

I see 3 approaches:

A – consciousness is a fundamental and irreducible thing. It can’t be explained in terms of the positions of atoms. So “KNOWLEDGE”, as a state of our consciousness, is also non-physical thing. Such interpretation is very interesting, but again, I have an impression that most of the CI proponents are close to materialism while their favorite interpretation is telling the opposite.

B – consciousness can be explained in physical terms, hence, it is just a state of a physical system. See above.

C – consciousness is irreducible but is NOT fundamental. It means that somehow consciousness is a product of our brain (and may be some other systems) but it is not possible, IN PRINCIPLE, to derive it from the functionality of the smaller parts. In another words, consciousness and the physical storage of it DO NOT COMMUTE: you can study the brain wiring, get an exact cell configuration, killing the brain in that process, and thus obtaining no information about the consciousness. You can study consciousness, but in that case your ability to dig into the wiring is limited.

It is possible that such limitation (non-commuting) is not instrumental (exactly like in QM), so no matter how tiny scalpels you use you can’t learn both things in the same time. It is possible that such limitation has no analogs in the simpler systems but emerge on some level of complexity, like Goedels theorem emerges at the level of natural numbers.

 

[Fra]

I'm not able to write any detailed responses now but maybe I see your objection now, I'll write more later but first of all I don't know what you mean by conscioussness in this context but I supposed you mean it's whatever acknowledges or justifies the collapse view?

In my view an observer is simply a physical system. No need for anything paranormal here, nor is there a need to dicsuss the biology of the brain. But that said, I think there are parallells here. But the parallell are no more hands on that the fact that some models physics and biology, apply also to economical systems.

I'd say your quest for a certain definition of the observers(measurement device) microstructure fails IMO because you are looking for a second view of an inside view. The only motivation for this, is because we want to predict our environment, and thus it is of our interest to understand how other systems act.

But what I am looking for here, is a process, not a static answer. Even a measurement device is under constant challange an evolution.

But part of my personal quest, I am considering a description of matter and physical law, and this implies the microstructure of observers. The construction and makeup of the physical observer (including particles and atoms) encodes a view of physical law, that govern how this observers behaves (it's interaction properties).

But this quest does not start IMO at an incredibly complex system such as a biological brain. Instead my reconstruction aims to start at the simplest possible distinguishable level, before the notion of a spacetime continuum. Then as the web of inferences proceed, there are some gradual emergenc of objectivity, what that is I don't know yet. But I suspect the spacetime dimensions and some TOE-level interaction are the first to pop up. Once the process proceed, the event space is expanding as the observer complexity scales, this will allow differentiation of hopefully the standard model forces.

In a way, this will provide an abstraction of the microstructure of the observer, like I think you want to see before buying this. But this is still nothing even near the human brain in complexity.

So in a sense, these "prototype observers" are in my view really just the simplest possible physical representation of physical law. I intuitively assocaite mass with the complexity of these constructs. Meaning as you let the mass of the observer goto zero, we reach the unification scale where all interaction becomes indistinguishable - from the inside view that is!

It's this process I seek. Along with it, QM will not survive with deformation, rather it should be emergent.

/Fredrik

 

[kote]

C – consciousness is irreducible but is NOT fundamental. It means that somehow consciousness is a product of our brain (and may be some other systems) but it is not possible, IN PRINCIPLE, to derive it from the functionality of the smaller parts. In another words, consciousness and the physical storage of it DO NOT COMMUTE: you can study the brain wiring, get an exact cell configuration, killing the brain in that process, and thus obtaining no information about the consciousness. You can study consciousness, but in that case your ability to dig into the wiring is limited.

I don't know that an irreducible consciousness can be said to be a product of our brain. That's one view, but it's not the only view.

Cogito ergo sum. I can know nothing more surely than the contents of my own thoughts and perceptions. How consciousness is related to the physical realm is interesting and is an open question, but it's beyond the scope of QM or Bohr's philosophy. There is no need to explain consciousness when there is nothing that we can know more surely than our own consciousness. Our doubt, our inquiries, will relate to external truths. Those are the ones science can tell us about. But when science "tells us" about something, it is adding to our knowledge. The fact that we exist to ask questions and to seek an expansion of our knowledge is taken for granted and needs no further explanation in this context.

We're talking about basic physics, not psychology. We're interested in gaining knowledge through the scientific exploration of external reality, which necessarily only presents itself to us subjectively. "What is consciousness" or "why is there consciousness" are beyond the scope. I exist to ask questions, so let me ask them .

 

[Dmitry67]

How consciousness is related to the physical realm is interesting and is an open question, but it's beyond the scope of QM or Bohr's philosophy. There is no need to explain consciousness when there is nothing that we can know more surely than our own consciousness.

This is why I don't like CI!

When asked about the wavefunction, CI proponents say: no, wavefunction is not real, it is only our knowledge about the system! It is not real, just information we know about the system

When asked about "what is that "knowledge" they've just said about and, how it is correlated with the state of the system-observer CI proponents smile and reply "Stop asking us these non-physical questions about the consciousness and knowledge! We are physicists, and it is about physics, not about the biology or psychology!"

It is not an interpretation. It is a way of hiding behind slippery and ambiguous words and self-recursive explanations.

 

[Fredrik]

This is why I don't like CI!

When asked about the wavefunction, CI proponents say: no, wavefunction is not real, it is only our knowledge about the system! It is not real, just information we know about the system

When asked about "what is that "knowledge" they've just said about and, how it is correlated with the state of the system-observer CI proponents smile and reply "Stop asking us these non-physical questions about the consciousness and knowledge! We are physicists, and it is about physics, not about the biology or psychology!"

It is not an interpretation. It is a way of hiding behind slippery and ambiguous words and self-recursive explanations.

For once I agree with most of what you say, but it's wrong to call this "the CI". You're only talking about option 4 on Demystifier's list. (And that's assuming I'm interpreting his 4 correctly).

 

[kote]

This is why I don't like CI!

When asked about the wavefunction, CI proponents say: no, wavefunction is not real, it is only our knowledge about the system! It is not real, just information we know about the system

Dmitry, I'm not sure any interpretation of QM explains consciousness. Bohm attempts to work it into his system, but I don't think he was very successful there.

Is it necessary that any scientific theory explain how it is that we understand it and know it? The question of how we know scientific theories seems to be to be entirely separate from the science itself. Different interpretations assume different epistemologies, but I don't see how any of them could prove the issue one way or another.

The fact is that we could be living in the Matrix or God could be presenting us with our experiences or any number of other things could be behind the scenes. We inherently can have no proof that this is not going on. We can only test how the "matrix" responds to our experiments. That's what science is about, and that's what Bohr is talking about when he says, "We meet here in a new light the old truth that in our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, so far as it is possible, relations between the manifold and aspects of our experience."

Whether or not you call aspects of our experience real is a question of semantics, and Bohr actually does allow for a large number of things to be called real, just not the wave function.

For once I agree with most of what you say, but it's wrong to call this "the CI". You're only talking about option 4 on Demystifier's list. (And that's assuming I'm interpreting his 4 correctly).

I'm not sure any of the CI founders thought the wave function represented anything besides knowledge of the system. Whether or not other aspects are real is a different question, and Bohr certainly believed in real classical entities. From http://plato.stanford.edu/entries/qm-copenhagen/" :

The quantum mechanical formalism does not provide physicists with a ‘pictorial’ representation: the ψ-function does not, as Schrödinger had hoped, represent a new kind of reality. Instead, as Born suggested, the square of the absolute value of the ψ-function expresses a probability amplitude for the outcome of a measurement. Due to the fact that the wave equation involves an imaginary quantity this equation can have only a symbolic character, but the formalism may be used to predict the outcome of a measurement that establishes the conditions under which concepts like position, momentum, time and energy apply to the phenomena.​

 

[DrChinese]

When asked about the wavefunction, CI proponents say: no, wavefunction is not real, it is only our knowledge about the system! It is not real, just information we know about the system

There is "evidence" that the wave function itself is real, although this can be interpreted in other ways too.

For example: you can play tricks with entangled beams, in which a measurement (perhaps via a polarizing beam splitter) is performed and then the result is "erased". The beams subsequently return to their entangled states. If the probability wave was not real, you shouldn't be able to do that - because collapse (due to the PBS) would be irreversible.

Of course, this assumes that for collapse, we know what occurs and when it occurs. To me, that is something of a weak element in CI.

 

[kote]

There is "evidence" that the wave function itself is real, although this can be interpreted in other ways too.

For example: you can play tricks with entangled beams, in which a measurement (perhaps via a polarizing beam splitter) is performed and then the result is "erased". The beams subsequently return to their entangled states. If the probability wave was not real, you shouldn't be able to do that - because collapse (due to the PBS) would be irreversible.

Of course, this assumes that for collapse, we know what occurs and when it occurs. To me, that is something of a weak element in CI.

What collapse ?

Complementarity is first and foremost a semantic and epistemological reading of quantum mechanics that carries certain ontological implications. Bohr's view was, to phrase it in a modern philosophical jargon, that the truth conditions of sentences ascribing a certain kinematic or dynamic value to an atomic object are dependent on the apparatus involved, in such a way that these truth conditions have to include reference to the experimental setup as well as the actual outcome of the experiment. This claim is called Bohr's indefinability thesis (Murdoch 1987; Faye 1991). Hence, those physicists who accuse this interpretation of operating with a mysterious collapse of the wave function during measurements haven't got it right. Bohr accepted the Born statistical interpretation because he believed that the ψ-function has only a symbolic meaning and does not represent anything real. It makes sense to talk about a collapse of the wave function only if, as Bohr put it, the ψ-function can be given a pictorial representation, something he strongly denied.

http://plato.stanford.edu/entries/qm-copenhagen/​

 

[DrChinese]

What collapse ?

Complementarity is first and foremost a semantic and epistemological reading of quantum mechanics that carries certain ontological implications. Bohr's view was, to phrase it in a modern philosophical jargon, that the truth conditions of sentences ascribing a certain kinematic or dynamic value to an atomic object are dependent on the apparatus involved, in such a way that these truth conditions have to include reference to the experimental setup as well as the actual outcome of the experiment. This claim is called Bohr's indefinability thesis (Murdoch 1987; Faye 1991). Hence, those physicists who accuse this interpretation of operating with a mysterious collapse of the wave function during measurements haven't got it right. Bohr accepted the Born statistical interpretation because he believed that the ψ-function has only a symbolic meaning and does not represent anything real. It makes sense to talk about a collapse of the wave function only if, as Bohr put it, the ψ-function can be given a pictorial representation, something he strongly denied.

http://plato.stanford.edu/entries/qm-copenhagen/​

I would say that when a photon goes through a polarizing beam splitter (PBS), then I would expect one of the following to occur:

a) the psi function collapses and a whole photon goes through one or the other of the PBS paths;

b) the psi function splits with 50% headed down one path, 50% headed down the other, but collapse does not occur until later when the photon is detected.

I think it is interesting that the 2 x 50% parts - i.e. b) - can later be reconstituted to create a 100% whole again; whereas the a) scenario you would not expect that since the collapse already occurred. So I would consider that as "evidence" for b) - and makes the psi wave relatively real and physical. (The reason I put evidence in quotes is because I know this is not an ironclad argument and is interpretation-dependent.)

 

[Dmitry67]

There is "evidence" that the wave function itself is real, although this can be interpreted in other ways too.

For example: you can play tricks with entangled beams, in which a measurement (perhaps via a polarizing beam splitter) is performed and then the result is "erased". The beams subsequently return to their entangled states. If the probability wave was not real, you shouldn't be able to do that - because collapse (due to the PBS) would be irreversible.

Of course, this assumes that for collapse, we know what occurs and when it occurs. To me, that is something of a weak element in CI.

Yes, but CI proponents would say "well, the first measurement was not a real one!" :)
THat is why I started a thread from example with a sequence of measurement devices.

 

[Dmitry67]

Is it necessary that any scientific theory explain how it is that we understand it and know it?

No of course
Only theories which explicitly uses high level things like "knowledge" must explain it.

Explaining QM via something, and then refusing to discuss that something for me is a synonym of admitting that one have no idea about it.

(My aggression is towards some imaginary CI proponent)

 

[Dmitry67]

For once I agree with most of what you say, but it's wrong to call this "the CI". You're only talking about option 4 on Demystifier's list. (And that's assuming I'm interpreting his 4 correctly).

Sorry, what list?

 

[kote]

I would say that when a photon goes through a polarizing beam splitter (PBS), then I would expect one of the following to occur:

a) the psi function collapses and a whole photon goes through one or the other of the PBS paths;

b) the psi function splits with 50% headed down one path, 50% headed down the other, but collapse does not occur until later when the photon is detected.

I think it is interesting that the 2 x 50% parts - i.e. b) - can later be reconstituted to create a 100% whole again; whereas the a) scenario you would not expect that since the collapse already occurred. So I would consider that as "evidence" for b) - and makes the psi wave relatively real and physical. (The reason I put evidence in quotes is because I know this is not an ironclad argument and is interpretation-dependent.)

I agree that this is exactly what you would expect if you were trying to visualize what's going on during the experiment. Bohr denies that such visualization is possible. You have the phenomenon of a particular experimental reading that depends necessarily on your experimental arrangement and whose description is incomplete without reference to the entire setup. Complementarity is defined by its unvisualizability. Thinking about what the photon does in the meantime, for Bohr/CI, is impossible. You can only talk about the entire setup. We think classically, and until you get that classical system output, everything is simply unintelligible.

 

[Fra]

Hence, the CI description “collapse of the (unreal) wavefunction changes our knowledge about it”

Did you really mean this or is it a typo? ie. knowledge about the wavefunction? (assuming it refers to wavefunction?)

As I see it, the wavefunction supposedly IS the structure for the knowledge. The hilbert space is the context for information to be define, and relative to that context, the wavefunction IS the information (encoded of course).

In this respect I'm with how Zurek put it - what the observer knows is indistinguishable from what the observer is.

The problem is here the assumption when you compose complex systems are products of hilbert spaces with separate wavefunctions. In my view, for a giver observer, there really is only one "system" to interact with and this is nothing less than the entire (unkonwn) environment, period. That's how I see it.

(That's close to Zurek, but I disagree with Zurek on other points.)

/Fredrik

 

[Dmitry67]

Fra, is Observer irreducable and fundametal?
In another words, can we write (in principle) very complicated function IsObserver(X) where X is any system, and IsObserver() returns boolean value?

 

[DrChinese]

I agree that this is exactly what you would expect if you were trying to visualize what's going on during the experiment. Bohr denies that such visualization is possible. ...

And of course now we have all kinds of exotic entanglement to consider, not available in Bohr's day. Strangely (to me), we can draw all kinds of ways to entangle things... but we can't see when or how or even whether collapse occurs.

But we know it when we see it.

 

[RUTA]

And of course now we have all kinds of exotic entanglement to consider, not available in Bohr's day. Strangely (to me), we can draw all kinds of ways to entangle things... but we can't see when or how or even whether collapse occurs.

But we know it when we see it.

What do you think about quantum eraser experiments?

 

[DrChinese]

What do you think about quantum eraser experiments?

Sure, I mean those are perfect examples of how difficult it is to ignore the role of collapse. On the one hand, you can still hold Bohr's view and there is nothing wrong with it. You simply look at the entire setup as one black box. On the other hand, we are talking about some pretty complex and exotic formats. Again, no issue with the formalism, just saying that it gets harder and harder not to imagine that you have to draw a line somewhere - and we can't seem to figure out where.

 

[Fredrik]

Yes, but CI proponents would say "well, the first measurement was not a real one!" :)

Or they would distinguish between "state preparation" and "measurement". A Stern-Gerlach magnet just prepares the system in a certain state.

Sorry, what list?

This one.

I agree with him. There's no clear set of axioms that defines "the CI". There is also no set of axioms that defines "the MWI", or any other "interpretation". (I think Bohm is an exception, but I don't know enough about it to say for sure). That's why I think almost everything that's been written about interpretations is meaningless nonsense.

 

[kote]

I agree with him. There's no clear set of axioms that defines "the CI". There is also no set of axioms that defines "the MWI", or any other "interpretation". (I think Bohm is an exception, but I don't know enough about it to say for sure). That's why I think almost everything that's been written about interpretations is meaningless nonsense.

Bohm is certainly not an exception . Well... let me clarify. David Bohm's view of quantum mechanics was very different from what we now call Bohmian Mechanics. Bohm himself had a relatively consistent (although organically developed) interpretation. Within the Bohmian Interpretation (as opposed to Bohm's Interpretation) there are still variations.

I think interpretations are meaningful, but they have been very confused. I think it's correct to say that there is no single CI in its present usage. There is certainly one consistent interpretation from Bohr though, which can be very different from what is called CI, similarly to how the Bohmian Interpretation is not Bohm's Interpretation.

 

[Fra]

Fra, is Observer irreducable and fundametal?
In another words, can we write (in principle) very complicated function IsObserver(X) where X is any system, and IsObserver() returns boolean value?

Ok I see. You wonder if there is something special about systems to qualify as observers?

IMO, no. Any system is an observer.

However not every _conceivable imagined_ system is a FIT - but then that's consistent with observations because matter is very structured (obeying symmetries etc, so it's not anything goes). Only fit observers are observed, like in nature there is a reason for why only particular speices populate the world.

So on one hand I'd say IsObserer(X) = true for any X. But I think the interesting question is which particular systems are selected to populate the universe.

It's like considering a mathematical imaginary theory were all kinds of twisted particles may possibly exist, and then ask why don't they? Here fitness and evolution of law comes in. IMO physical law is encoded in the microstructure of the systems that does populate the universe.

So evolution of law is the other side of the coin to evolution of physical systems.

The answer lies in understanding the evolutionary process, like Darwins theory in biology. Each environment selects it's preferred inhabitants, the circularity lies in the fact that the environment IS a collection of many inhabitants. But this understanding is not worked out yet. Solve that problem and we should see some answers to what constrains not just observers but ANY physical system, which is basically the question for the structure of matter I believe.

/Fredrik

 

[Fra]

Fra, is Observer irreducable and fundametal?
In another words, can we write (in principle) very complicated function IsObserver(X) where X is any system, and IsObserver() returns boolean value?

The way I envision this program - which I think is the only consistent way I know of - is that the reconstruction of a probability theory(*) I imagine will also be a reconstruction of the makeup of viable physical systems, and thus observers.

The physical systems in nature are not arbitrary, as we know from the standard model. So indeed "any system" is already constrained if we count only those that we see in nature, and the constraints of "any system" is the same that qualifies them to be a "physical observer". So given that "the system" is constructed in a physical process (and not just beeing made up in some wild theory) then all physical systems qualifis as observers. That's my view.

(*) Since I share part of the spirit of Jaynes and Ariel, I think that somehow probability theory is an extension to logic and indeed the logic of science and reasning, but only sort of! The current continuum probability makes no sense. So the reconstruction I imagein, is really a reconstruction of a more physical measure theory, and in my interpretation and observer or a system IS thought of as a measure-complex. This measure complex is a generalisation and replacement of the hilbert space abstraction. Actually I expect there to be a one to one mapping from one measure-complex to one hilbert space, but the problem is that hilbert spaaces are normally thought of as qualifiying context. In my view the measure-complexes are embodied by observers, and these are evolving. So in my view hilbert spaces are evolving - which is why I find hilbert space the first axioms of ordinary QM to be inappropriate.

So I am working on an extension/reconstruction of probability theory which is the basis for statistical physics and classical thermodynamics. The new "information-complex" theory will (this is my conjecture) like classical probability leads to thermodynamics, lead to ordinary physics with much more complex interactions. The classical state space corresponding to a probability space, is replaced by a measure-complex (a system of related discrete spaces) which in a differential sense corresponds to hilbert spaces.

This plan, implies also that the actions or hamiltonians are encoded in the measure-complexes simply as natural diffusion type actions. The measure complex vs simple probability space is what I expect will make the interaction nontrivial and diverse, rather than just diffusion type like in thermodynamics.

/Fredrik

 

[Fra]

B – consciousness can be explained in physical terms, hence, it is just a state of a physical system. See above.

Given your choices, B is my closest match. (if I replace conscioussness with observer here)

But if we say, an observer is just a physical system, then the question how an observer works, amounts of question how a physical system works - ultimately questioning matter and it's physical action pattern.

/Fredrik

 

[Fra]

But this is no clean CI. I sure don't rely on a classical reality in my view. I rely on the only think I can rely on - my prior structure and state. So, my actions are as if, this was classical reality. But my actions are (in the differential sense) indifferent to wether my view matches those of my fellow neighbouring systems. If not, I will be informed about this from feedback from my environment. One step at a time. To take one step, I do not need to know what's 100 steps ahead. Only my expectation guides me, and I think the same applies to physical actions. This is a form of locality of information. Only information at hand, influences your action. This does however not say much about the future. By I think evolution works from the present.

/Fredrik

 

[Fra]

How's this derivation of the CI?

Zurek, http://arxiv.org/abs/0707.2832 : "Finally, we point out that monitoring of the system by the environment (process responsible for decoherence) will typically leave behind multiple copies of its pointer states. Only states that can survive decoherence can produce information theoretic progeny in this manner."

There's too much to object to there in there. The axioms he start with about the hilbert spaces are unacceptable starting points. This represents a nontrivial baggage. So instead I'll note what I like.

- On his idea of the environment as an information pool, in which copies of an interacting system is propagated and reproduced is I think very good. This conceptually makes excellent sense. I'd argue thta this applies not only to copies of states, but also copies of the action, that the environment also evolves a consistency with the systems action/interaction properties, and thta this can be thought of as the DNA of physical law. This could be extended to an alternative way of implementing evolving law, that is different from smolins CNS. This is then very close to my thinking.

So what I mean is that by interacting with the environment, you're not merely spreading your word (ie copying your state) you are also spreading your REASONING, ie copying your action, and this is close to the DNA of physical law (which would be symmetries in the action), and this can explain how evolution of law works, in a quite more interesting way than the CNS.

An environment that is equilibrated as per a particular symmetry, would then by selection favour growth of "consistent" systems.

My main objection is that a lot of the premises, used to make the inference Zurek does, is IMO no different than other information. So I think Zurek is still fairly conservative here. I think we need to be more radical to gain more predictive power.

/Fredrik