Question about the perception of collapse in relational to QM interpretation

[evi7538]

TL;DR Summary

Perception of the collapse in relational to
QM interpretation

I'm diving into the RQM and one thing still puzzles me. I have hard time understanding this:
Taking the model system discussed above, if O′ has full information on the S+O system, it will know the Hamiltonians of both S and O, including the interaction Hamiltonian. Thus, the system will evolve entirely unitarily (without any form of collapse) relative to O′, if O measures S. The only reason that O will perceive a "collapse" is because O has incomplete information on the system (specifically, O does not know its own Hamiltonian, and the interaction Hamiltonian for the measurement).

Let's assume a Shrodinger cat scenario where S is the system of a photon and a cat, O is their observer, and O' is the observer of S+O. Until O' makes an observation of the S+O system, the S+O system goes into in the state of
|↑⟩|obs⟩→1√2(|←⟩|obs←⟩+|→⟩|obs→⟩)
which is a superposition. However, if O is not only a measurement apparatus but also includes the consciousness of the observe O, then the consciousness registers only one specific state (cat dead or alive, because we know from our conscious experience that we would never experience a superposition of two distinct macroscopic states).

So the QM (in RQM interpretation) tells us that S+O only exists in a superposition of two states, but the consciousness of O registers/experiences only one of those states (which is the same as to say that it perceives the collapse). Is this because as a result of S+O interaction the probability of one of the states (|←⟩|obs←⟩ or |→⟩|obs→⟩) becomes so infinitesimally small (due to the macroscopic scale of the S+O Hamiltonian) that it becomes undetectable? Does this mean that the consciousness of O would actually be able to experience the superposition if both probabilities would be high enough to be simultaneously detectable? If this assumption is true, can we construct an experiment in which we can make both probabilities high enough to be detectable by the consciousness of O so that O could experience the superposition? Or am I missing something here?

 

[PeterDonis]

the consciousness registers only one specific state (cat dead or alive, because we know from our conscious experience that we would never experience a superposition of two distinct macroscopic states)

Whether or not we do in fact know this is interpretation dependent. On the Many Worlds Interpretation, it is not the case that your consciousness registers only one specific outcome (cat dead or cat alive). On the MWI, your consciousness goes into a superposition of "experiencing that the cat died" and "experiencing that the cat is alive". More precisely, your consciousness becomes entangled with the cat and the apparatus and everything else, so that there are two branches of the overall wave function, one in which the cat is dead and you experience the cat being dead, and one in which the cat is alive and you experience the cat being alive.

RQM is sort of the same idea, but without any commitment to the claim that there must be a single, global "universal wave function". In the RQM version of the above, you have to imagine, in addition to the "you" (O) that is in each "branch", another observer (O') who has complete information about the overall Hamiltonian and watches the cat experiment from the outside. To the observer O in each branch, the state has collapsed and the cat is either dead or alive, and that is what they experience. But to O', the whole system is evolving unitarily, there has been no collapse, and there are two "branches", one with a dead cat and an O who experiences the cat being dead, and one with a live cat and an O who experiences the cat being alive.

(Note, however, that O' does not have the same overall view of systems of which he himself is a part. For example, if O' became the observer in a second Schrodinger's cat experiment, he would experience the cat being dead or alive, just as O does in the first experiment, but there could be some third observer, O'', who knows the overall Hamiltonian for the O' cat experiment, and sees two "branches", one with a dead cat and an O' who experiences a dead cat, and one with a live cat and an O' who experiences a live cat. And we could do the same with O'', and so on ad infinitum, never reaching any single overall wave function or state or Hamiltonian that includes everything. That is where RQM, as I understand it, differs from the MWI.)

can we construct an experiment in which we can make both probabilities high enough to be detectable by the consciousness of O so that O could experience the superposition?

No. O, being "inside" the experiment, cannot have complete knowledge of the overall Hamiltonian, so he won't experience himself being in a superposition. Only the "outside" observer, O', can see the superposition, and it doesn't include him.

 

[evi7538]

Right, what you said is correct from the point of view of MWI or RQM, whichever interpretation we take. But here is where the problem is. In RQM it contradicts with the fact of our direct conscious experience that we always experience only a single state and never a superposition. This is because in RQM the universe does not branch, and so my consciousness (if I'm O) also does not branch, there is always only one instance of the universe and only one instance of my consciousness. But RQM says that a single instance of my consciousness actually exists in a superposition of two states, which contradicts to my direct conscious experience of experiencing always only a single state and never a superposition.

In MWI this is not a problem because my consciousness also in fact branches into two instances (together with branching of the worlds), each instance experiencing only a single state, so it does not contradict with the direct conscious experience of each of the instances of "my" consciousness. (Well, technically there would be two instances of "me" as well, so the question which one is "mine" would be meaningless).

No. O, being "inside" the experiment, cannot have complete knowledge of the overall Hamiltonian, so he won't experience himself being in a superposition.

OK, this is what I don't get. What does my conscious experience has to do with knowing the Hamiltonian? I know for a fact that I experience only one state, while O' sees me (including my consciousness) in a superposition, which means that within this superposition there must be a state of my consciousness experiencing the second state. But there is only one instance of my consciousness here, so why I am not experiencing both states simultaneously then?

Or may be, in the spirit of RQM, we can say that the fact that I (the observer O) experience only one state of in my conscious experience does not contradict with the fact that O' observes a superposition of two states, because there is no such thing as an observer independent quantum state? But still the fact that I experience only a single state requires an explanation because somehow the second state (from my O's point of view) collapses. But how does this collapse exactly happen? Here we would have to refer again to the mysterious decoherence caused by the macroscopic scale of the S+O Hamiltonian, so we would be back to the same decoherence/collapse problem faced by the Copenhagen interpretation.

I think when we assess the consistency of different QM interpretations and their agreement with the experimental facts, we should also include the experimental facts of our conscious experience, not just the facts of the measurement results of the physical instruments. In that sense the RQM seems to me to be inconsistent with the facts of conscious experience, while MWI is still quite consistent.

 

[PeterDonis]

In RQM it contradicts with the fact of our direct conscious experience that we always experience only a single state and never a superposition. This is because in RQM the universe does not branch

No, this is not correct. What is correct in RQM is that the concept of "the universe branching" makes no sense, because there is no single quantum state for the universe. All quantum states are relative to an observer. So in the RQM version of the Schrodinger's cat experiment, with observer O' looking in from outside, you actually have three quantum states: the state relative to the observer O who experiences a dead cat, the state relative to the observer O who experiences a live cat, and the state of observer O' who sees that there is an entangled system of O and cat that is in a superposition.

The point of RQM is that there is not, and doesn't have to be, any single global state that somehow ties the three states above together. There are just those three states period. In the first two states, there is no "branching"; in each one there is an observer O who experiences a single consistent sequence of events. The fact that those two sequences of events, for the two different observers O, are inconsistent with each other is, according to RQM, irrelevant, because they don't have to be consistent with each other, they only have to be consistent within themselves. In the third state, there is "branching" in the sense that the entangled O-cat system evolves unitarily into a superposition, but that does not mean the entire universe branches. The "branching" is only in the state relative to O'.

may be, in the spirit of RQM, we can say that the fact that I (the observer O) experience only one state of in my conscious experience does not contradict with the fact that O' observes a superposition of two states, because there is no such thing as an observer independent quantum state?

Exactly. See above.

the fact that I experience only a single state requires an explanation because somehow the second state (from my O's point of view) collapses. But how does this collapse exactly happen?

RQM does not, as far as I can tell, say anything specific about this beyond the basic math of QM.

in that sense the RQM seems to me to be inconsistent with the facts of conscious experience

No, it's not, it's just a different sort of explanation of them from other interpretations. The quantum state being relative to an observer does not mean the "observer" has some sort of privileged status. Each "observer" is just another quantum system, interacting with other quantum systems. That includes conscious observers. A better way of stating what RQM is saying might be that the quantum state is relative to the particular set of quantum systems that are interacting, and what the outcomes of those interactions are.

 

[PeterDonis]

the mysterious decoherence

Decoherence, in itself, is not mysterious; it's just what you get when you apply the basic math of QM to a quantum system with a small number of degrees of freedom, interacting with an "environment", which is just another quantum system with a very, very large number of degrees of freedom that cannot be kept track of.

Whether or not you think decoherence solves the quantum measurement problem is a separate question.

 

[evi7538]

No, this is not correct. What is correct in RQM is that the concept of "the universe branching" makes no sense, because there is no single quantum state for the universe. All quantum states are relative to an observer. So in the RQM version of the Schrodinger's cat experiment, with observer O' looking in from outside, you actually have three quantum states: the state relative to the observer O who experiences a dead cat, the state relative to the observer O who experiences a live cat, and the state of observer O' who sees that there is an entangled system of O and cat that is in a superposition.

Right, I get it. But to me there is still a cognitive gap here, because based on the fact of my direct conscious experience there is always only one "me" experiencing only one state (of either dead or alive cat). While the statement above indicates that there are two experiences going on simultaneously to the same single observer O (me).

 

[PeterDonis]

based on the fact of my direct conscious experience there is always only one "me" experiencing only one state

Yes, and everything in the state you are experiencing is relative to that "you", the one who is having that direct conscious experience of all the quantum systems you are interacting with. But you have no way whatever of knowing about states of quantum systems that you are not interacting with. It could even be that those other states, that you are not interacting with, include a quantum system that has the same past experiences as you do, up to the point where you observed the cat; then that quantum system observed the opposite result from the one you did. That quantum system would also think of itself as "you", but its memories and experiences would be different from yours after the point at which you observed the cat. And that quantum system would also be interacting with another quantum system that had the same history as the cat up to the point where you observed the cat, when its state would diverge from the state of the cat that you are interacting with.

At least, all that is what RQM says is happening, and there is nothing in the math of QM that is inconsistent with it.

the statement above indicates that there are two experiences going on simultaneously to the same single observer O (me).

No, it doesn't. See above. You are not being careful enough about distinguishing the proper referent of the terms "you" and "me" in this scenario. Our ordinary language was not designed to describe this kind of thing, so you have to be extra careful to treat even the most common ordinary words as technical terms that might not mean quite what your intuition thinks they ought to mean.

 

[evi7538]

It could even be that those other states, that you are not interacting with, include a quantum system that has the same past experiences as you do, up to the point where you observed the cat; then that quantum system observed the opposite result from the one you did. That quantum system would also think of itself as "you", but its memories and experiences would be different from yours after the point at which you observed the cat. And that quantum system would also be interacting with another quantum system that had the same history as the cat up to the point where you observed the cat, when its state would diverge from the state of the cat that you are interacting with.

OK, thanks, I get it, but I can only take it as a hypothesis (together with the RQM whole package which is also only based on hypotheses). We know from our conscious experience that we have a unitary "space" of conscious phenomena (qualia), the space of awareness, that we usually linguistically refer to as "me". So I can see an implicit assumption (hypothesis) in your explanation that different quantum states give rise to distinct "spaces" of qualia that do not overlap with each other, or in other words, are not experienced within the same unitary space of awareness. So, the space of awareness is getting split into a set of spaces according to the set of quantum states. This assumption is necessary to make RQM consistent with the conscious direct experience, but it is not self-obvious and cannot be derived from other principles of RQM. So I think if we are to include consciousness into the RMQ, we would need to add this assumption into the set of two RQM basic hypotheses.

This hypothesis is in a way similar to MWI but only applies to the realm of consciousness, while MWI applies to the physical realm as well. In a way, it can be seen as "many conscious worlds" interpretational extension to the standard RQM. The bottom line is: to make QM consistent with the data of conscious experience, we have to assume the hypothesis of "branching" the space of consciousness (while with respect to the physical world we can, but do not have to assume the branching of the physical universes as done in MWI).

At this point we come to the border of interaction of quantum systems with consciousness, and to the mechanism of how exactly quantum states give rise to the qualia of conscious experience, which is the subject of the "hard problem of consciousness" ((c) David Chalmers). Nobody had so far even a slightest clue or any sensible explanation of how exactly this happens.

 

[evi7538]

Decoherence, in itself, is not mysterious; it's just what you get when you apply the basic math of QM to a quantum system with a small number of degrees of freedom, interacting with an "environment", which is just another quantum system with a very, very large number of degrees of freedom that cannot be kept track of.

Whether or not you think decoherence solves the quantum measurement problem is a separate question.

Right, but as far as I know, the decoherence hypothesis is still mathematically incomplete and unproven, that's why I called it "mysterious". Also, the collapse hypothesis (also mathematically unproven so far as far as I know) is a stronger statement than decoherence. Decoherence is statistical averaging of the phase/interference terms in the quantum states, while keeping the probability densities of distinct eigenstates still high. Collapse is not only that, but in addition diminishing the probability densities of all eigenstates except for one dominant states to negligibly small values.

 

[evi7538]

No, it doesn't. See above. You are not being careful enough about distinguishing the proper referent of the terms "you" and "me" in this scenario. Our ordinary language was not designed to describe this kind of thing, so you have to be extra careful to treat even the most common ordinary words as technical terms that might not mean quite what your intuition thinks they ought to mean.

I agree, but in this scenario we do have an experiential referent of the term "me". Basically, as I said above, the term "me" is simply a linguistic pointer to the experiential unitary "space of awareness" in our direct conscious experience that includes a multiplicity of conscious qualia that we experience every moment in our direct experience. All this qualia are different from each other but share the same quality - the are being "awared" simultaneously within one "space of awareness" at the same moment.

So, two different quantum states occurring at the same moment would give rise to different qualia of conscious experience that would also co-exist at the same moment. But we do not observe such co-existence in our actual conscious experience. Therefore, to make QM interpretations consistent with the experiential data of our direct conscious experience, we have to assume one of these hypotheses (or there may be others, but these two come to my mind):

1. The qualia caused by different quantum states are in fact experienced and present in a certain actually experienced space or spaces of awareness, but the spaces of awareness corresponding to different quantum states do not overlap ("many conscious worlds" interpretation extension hypothesis).

2. There is only one actually experienced space of awareness per each distinct quantum conscious observer with qualia that correspond to only one of the quantum states, the rest of the possible qualia corresponding to the other states are collapsed and are not experienced in any actual space of awareness. This hypothesis requires a rigorous mathematical demonstration of how exactly this collapse happen.

3. A slight modification of the previous one: There is only one actually experienced unitary space of awareness per each distinct quantum conscious observer, in which ALL possible qualia corresponding to all possible quantum states are actually present, but only one set of qualia corresponding only to one quantum state are experienced distinguishably, the rest of the qualia corresponding to other quantum states are too weak to be distinguished above the noise floor of the perception of conscious qualia (in other words, they do not collapse into non-existence, they are still present in the space of awareness, but simply collapse below the noise floor threshold of conscious perception and become indistinguishable and non-detectable). Possibly the "intensity" of the qualia are somehow monotonically related to the probability densities of the quantum states. But since this scheme is still based on the collapse hypothesis, it still requires a mathematical explanation of how the probabilities of all other states except the one dominant state get "collapsed" (diminished) under the threshold of conscious detection limit.

Hypothesis #2 actually seems unlikely to me, because it is hard to imagine how the "collapse", being a mathematical transformation of the wave function of the object+observer system from two non-interacting states of the object and observer into an entangled object+observer state, can lead to zero probability densities of the rest of the states except for the dominant one. I can imagine the probability densities diminishing to practically undetectably small values, but it's hard to believe that they all can collapse to actual zeros. It would be interesting to attempt to prove it mathematically.

Interesting that, being independent extensions to the standard QM interpretations, each of these hypotheses can be mixed with almost any of the standard QM interpretations (may be some pairs are incompatible, I need to look more closely).

 

[PeterDonis]

I can only take it as a hypothesis

Of course, that's going to be the case for any interpretation, since it is going beyond the actual predictions made by the math and trying to tell a story about what is going on behind the scenes that can't be observed.

two different quantum states occurring at the same moment would give rise to different qualia of conscious experience that would also co-exist at the same moment

Co-exist in the overall quantum configuration space. But the overall quantum configuration space is not the same as ordinary space. There is a lot more "room" in configuration space, including room for multiple distinct degrees of freedom in the same physical location (same coordinates in ordinary space), which can contain different conscious observers (who might share memories up to a certain point in the past), as long as the degrees of freedom corresponding to the conscious observers are entangled with other degrees of freedom at different physical locations (and those other degrees of freedom will then contain different "versions" of the objects that the different conscious observers have observed). You are not taking that into account.

we have to assume one of these hypotheses

No, you need to go back and rethink your entire approach based on a proper understanding of the quantum configuration space, per the above.

 

[evi7538]

No, you need to go back and rethink your entire approach based on a proper understanding of the quantum configuration space, per the above.

There is a lot more "room" in configuration space, including room for multiple distinct degrees of freedom in the same physical location (same coordinates in ordinary space), which can contain different conscious observers (who might share memories up to a certain point in the past), as long as the degrees of freedom corresponding to the conscious observers are entangled with other degrees of freedom at different physical locations

This is correct and consistent in the context of the QM math when we talk only about physical objects and the Hilbert space of their quantum states. Don't assume I do not understand it, it is pretty clear. But things crucially change once the conscious experience gets into the picture, because the qualia of conscious experience are not necessarily quantum states, they are actual conscious experiences. In your statement you are already assuming that the space of quantum states at the same moment and the same spatial location contains a set of different conscious observers (in other words, a set of non-overlapping spaces of conscious experience), one per each eigenstate. But this assumption is not self-obvious at all, it is based on a specific hypothesis (#1 in my list) that you implicitly make, and this is not the only unavoidable alternative, there can be other assumptions.

 

[PeterDonis]

If you think the qualia of conscious experience are not quantum states, then this discussion is pointless because QM and its interpretation can say nothing about the qualia of conscious experience.

 

[PeterDonis]

Right, but as far as I know, the decoherence hypothesis is still mathematically incomplete and unproven, that's why I called it "mysterious".

Decoherence is not mathematically unproven. Collapse is, but as you correctly note, collapse is a much stronger claim than decoherence.

 

[PeterDonis]

This hypothesis is in a way similar to MWI but only applies to the realm of consciousness

This is not correct. RQM does not say that quantum states are relative to particular conscious observers. It says that quantum states are relative to particular sets of quantum systems that are interacting with each other. There is no requirement that the interacting quantum systems contain conscious observers; the same account given by RQM applies whether they do or not.

 

[evi7538]

If you think the qualia of conscious experience are not quantum states, then this discussion is pointless because QM and its interpretation can say nothing about the qualia of conscious experience.

This is not correct. RQM does not say that quantum states are relative to particular conscious observers. It says that quantum states are relative to particular sets of quantum systems that are interacting with each other. There is no requirement that the interacting quantum systems contain conscious observers; the same account given by RQM applies whether they do or not.

I agree, and not only that, but we can make even a stronger statement that QM and its known interpretations as they are currently formulated are simply not applicable to the qualia of conscious experience and to any correlations between quantum states of systems and the qualia. Therefore, we have to either explicitly exclude any conscious observers from the QM framework, or, if we want to include conscious observers into the QM framework, we have to extend the QM interpretations with certain additional hypotheses.

 

[PeterDonis]

we can make even a stronger statement that QM and its known interpretations as they are currently formulated are simply not applicable to the qualia of conscious experience

No, we cannot make such a statement. We can only say that QM and its known interpretations will not be accepted as complete by people, like yourself, who do not consider it possible that quantum states can include the necessary degrees of freedom to describe the qualia of conscious experience, because you do not consider it possible that entangled states such as we have been discussing can describe the qualia of conscious observers. But there is nothing in QM that forbids that possibility.

 

[Demystifier]

but as far as I know, the decoherence hypothesis is still mathematically incomplete and unproven, that's why I called it "mysterious".

No, decoherence is an experimentally verified fact, for which a Nobel prize (2012) has been awarded.

 

[evi7538]

But there is nothing in QM that forbids that possibility.

OK, fair, I agree that QM by itself is neutral to the phenomena of consciousness.

No, decoherence is an experimentally verified fact, for which a Nobel prize (2012) has been awarded.

Thanks, it appears that my knowledge in this area is quite outdated.

Thanks to all for a good discussion, I now have better understanding.