Painting a QBist Picture of Reality

Thanks Georgina, I'll read that article.

Thanks for that link, Georgina. I quote from that article, amongst several other quotable Fuchsisms, "As QBism understands a quantum measurement outcome, it's personal. No one else can see it." I see this quote as problematic as a description of experimental practice. In days of Bohr, indeed someone looked at a meter needle and no one else looked, but now it's almost universally a computer that looks and anyone can look at what the computer recorded.

Still the best example (IMO, it's nontrivial, at the right level for QBism in that it's modeled by a low-dimensional Hilbert space, but starting to be a little old) is the collection of datasets generated by Gregor Weihs in the experiment described at length in his thesis and in PRL (for which see https://arxiv.org/abs/quant-ph/9810080). Anyone can look at a classical copy of the same data Gregor looked at (he's become unwilling to let just anyone analyze the data, but for a few years it was freely available), which for each run of the experiment consists of two lists of times at which Alice's and Bob's detectors, 400 meters from each other in the apparatus, switched from current off to current on (plus which detector current changed and the state of the polarizer at the time).

If one feels that one has to think in terms of wave function collapses, Gregor didn't cause any collapses, perhaps we could say that he set up a computer to cause some collapses. We can, however, consider the circuits of Gregor's experiment in more detail, asking what the detector signals would have looked like at the picoAmp and picosecond scale, say (Terabytes of data per second), in which there would be identifiable changes of state --collapses, much less data to record-- but changes of the detector current are nonetheless rather closer to continuous --not so much collapses.

There is a question how to manage the relationship between the experimental datasets and the expected values that are generated by Hilbert space models, where we might choose Bayesian methods as one particular approach, but there are many ways in statistics to estimate model parameters.

Someone might feel like responding substantively here on FQXi? Is there other literature on QBism that discusses experiments in a more world-like-way than Chris Fuchs uses here?

Having now read the comments on the Quanta article you linked to, Georgina, just one comment there alludes to the qualm I express above, "There is an objective reality; it's on a server somewhere. We each have our own copy to hack as we want. Why the quantum? Because pixels." At least, the first sentence, maybe the rest is too tongue in cheek, too little detail. One could say that an experiment only becomes part of science when it's published in a journal, ideally with supplementary datasets that allow the conclusions to be discussed in detail; then, it's on a server.

I also looked at a paper linked to by Blake Stacey there, https://arxiv.org/abs/1301.3274. The idea that QBism wants to take the KFC approach, that QBism's B stands for whatever I or you or Chris Fuchs says it stands for, falls rather by the wayside in the focus on SICs, more than hinted at at the end of the Quanta article. QSICism, hinting at "thus" or "just as", has a problematic sense. It doesn't have the same ring, but the mathematics, in contrast to the metaphysics, is kinda-maybe QPEism, Quantum Parameter Estimation-ism, allowing that one might use a Bayesian approach, but also allowing other statistical methods, when constructing Hilbert space models for experimental descriptions, which can be said to determine a prior before the experiment is run, and the resulting datasets.

The question of when the wave-function can be said to have collapsed is of interest to me. I have submitted a paper to viXra that posits that rather than an unmeasured electron having multiple spins represent-able by the wave-function, that it is encountering conditions within the apparatus that induce the detected behaviour. I have called that provocation rather than measurement. The outcome becomes inevitable at provocation but is not known about until the observer receives information, by which the result is known. Thus there is an un-named duration in which the wave-function of multiple states no longer applies prior to the observer knowing the result. However if the wave-function is considered to be only a state of knowledge and not the reality of the external system outside of the mind, then the wave-function can not be said to collapse until the state of observer knowledge is updated by the new information. If the state observed is considered to have been provoked, the wave-function was a representation of the many possibilities that might have been, the multiple (not yet existent) possibilities, eliminated by the provocation. The term wave function redundancy might be useful to denote the situation post provocation but prior to the observer update and final designation of collapse or no further applicability of the wave-function of multiple states to the observer observed system ensemble.

Also interesting is whether probabilities have any claim to being a part of reality. They relate to possibilities and potential. I have put those two on the border of Object reality between what does and does not yet exist on my diagrams. Yet there are two kinds of possibilities or potential. 1. might be-s that do not yet exist ( as shown on my diagrams) and another class, 2. unknowns that do exist. eg. the unmeasured spin of a globe. In the case of electron spins I think it is not that they do all co-exist but that the possibility of getting a detection of any of them is not excluded by the existing Object reality, until provoked by interaction with the apparatus, into producing one 'spin" outcome. So the first kind of possibilities.

'Exist' is the wrong word to use for spin of a globe, a kind of motion not a thing. I should have said- 'Unknowns that do exist or are happening'.

Georgina, I doubt I can be very helpful, but I'll try... Am I right that your intention is to call the events that are recorded as part of an experiment "provocations" instead of "measurements"? It's not clear to me from your discussion how one differs from the other. In particular I can't see any instrumentalist difference, in that the same datasets will be recorded for later analysis, but I also can't see in your account what difference of metaphysics you intend?

Reading my PoV into your account, measurement events are a consequence of including a macroscopic, meta-stable thermodynamic system as part of an experimental apparatus. An event happens when the electric resistance (or some other thermodynamic property) of this relatively large assemblage changes, and the amplified current is enough to be recorded, together with a time-stamp, in a computer memory somewhere. If the macroscopic, meta-stable thermodynamic system were not there (as a provocation, if you will, but I don't like this coining much), there would have been no event to record in the computer memory, and hence no datasets that we can use to verify that quantum theory correctly predicts events. One has to keep in mind, however, that not all the usefulness of quantum theory derives from records of discrete events.

I think I read your second comment just to say that you're not sure whether probabilities are "real". FWIW, my take is that probability distributions are parts of mathematical models, which have a typically slightly equivocal, less than completely formal relationship to datasets containing raw experimental results (which are still mathematical objects, but with significantly less mathematical structure; they're typically just large but finite lists of numbers). The World --perhaps we might even call it The Real World-- is not to me obviously a Mathematical Object, though perhaps it is; however I've never been able to see a way to determine whether it is or is not.

Whether this is helpful or not, Best Wishes.

Joe, I am deleting your posts because you are blanket posting the same message over and over again. I find your behaviour inconsiderate and tedious. I have tried discussing your ideas with you and have read and commented on your essay. You have not been ignored or had your idea suppressed. Your essay has been accepted for the contest and is available for anyone who is interested.Its just that enough is enough.

My feeling about Qbism is that it is in a long line of ideas about physics that leap off into philosophy. Quantum interpretations are all ways of trying to make metaphysical or existential categories fit with quantum mechanics. In general these fit into two sets ψ-ontology and ψ-epistemology. The big example of the first of these are the Everett-DeWitt Many Worlds Interpretation,. While less popular the Bohm interpretation is also in this set. The main example of the latter is the Copenhagen interpretation. Qubism is pretty clearly a case of ψ-epistemic interpretation. These all have some utility in working certain problems. I also think they are all ultimately flawed. The reason is that with quantum mechanics we can only talk about outcomes that are real valued as having ontology. Quantum mechanics is complex valued, which means there are formal aspects of QM that can't be expressed in ordinary language that fits within these categories completely.

ψ-epsitemic interpretations have the problem that Heisenberg pointed out with Bohr's insistence on a quantum vs classical divide. Where does this exists? The Schrodinger cat and other arguments are meant to illustrate this difficulty. Much the same holds with Qubism, where the observer's perspective is considered central. However, who or what is an observer? I can consider myself to be an observer, but I am different with every breath I take, or with each meal or every time I use the bathroom. Where is the cut-off with the observer? How is the observer that distinguishable from the rest of the world? If I find cosmic ray tracks in multi-billion year old rock am I really measuring a wave function collapse? I could say in some way that I plus the rock over billions of years are a composite as an observer. However, does that really change what happened quantum mechanically with the reduction of states in the rock? At some point this starts to sound less like physics and more like philosophy.

Quantum interpretations are starting to multiply like bunnies, and there seems to be no clear way to indicate which one is (ones are?) correct. The workshops and conferences on these things grow in size and number, but as I sense things they all seem to be like meetings of philosophers arguing the truth of some point based on clever use of language. Polls are sometimes taken at meetings or conferences of physicists on QM interpretations. There is always a split and this changes a bit with time, but no interpretation appears headed for becoming the clear winner. Some are very popular right now, such as MWI, and others are in the dumps such as Bohm's QM. Bohm's QM has problems but it is not as horrible as people think.

There is in a sense one interpretation, which is the null-interpretation. QM can only interpret itself, not us. I think this is tied into the prospect that a quantum measurement as a quantum system plus quantum apparatus (apparatus ultimately made of quantum states etc) is a quantum information or quantum Turing case of Godel's theorem. QM lacks the power to predict a specific outcome, only probabilities for the outcome of some observable (Born rule etc), and there does not exist a quantum interpretation that will close off QM in a consistent manner with measurement or the existence of a classical (classical-like really) world. The so called quantum measurement problem will never be solved.

Peter,

Measurement is of an already existing or happening, property or behaviour. Provocation causes the behaviour or property of the thing to come in to being or happen.The difference is not in the results but in how we think about what is going on.

Thanks, Georgina. Do you take "existence" to be a property that only happens after provocation? If an individual event is provoked, does the particle that is said to cause the event exist only at the moment of the event, not before or after? If so, is a particle a synonym for an event? Or how is a particle different from an event? Too many questions! Choose any or none.

There's a slight feel of contextuality to your proposal, though enough differences are apparent to me that I won't ask you to delineate what differences you see.l

I take existence to be only at one time, not spread over time. I am not using events as I think you intend the word to mean , i.e. as space-time co-ordinates. My proposal is that provocation induces the state measured, that state being a behaviour in response. the electron isn't carrying X,Y and Z spins but if its just a random electron, just moving. I imagine how it happens to be moving interacts with the fores encountered to give an outcome then referred to as a spin.

It seems to me the wave function collapse is a switching of model used to represent reality. The interaction with the apparatus that makes the outcome inevitable is something happening in the foundational Object reality that is not observable so separate from the observer awareness pre- and post result ( and pre and post models of reality.) Just because the "redundancy" is taking place prior to information receipt by the observer doesn't mean it isn't happening. I'm not sure if that is at all similar to your line of thought re. the computer.

Thinking about the computer registering a detection; it can happen faster than human awareness. So it might be said that it registers "redundancy" of the wave function prior to "collapse ". Using the idea that "collapse" is when the physics model is updated (by the physicist) using the received information. I think there is some usefulness in separating the moment of inevitability of outcome ("redundancy")from the moment of receipt of transmitted information about it, ("collapse")- i.e. altering the description of the physics by the conscious receiver. Though it could all be automated and the computer could report the state that was detected but that report might not be immediately read. So maybe "collapse" could be said to be at the report making. I don't think the when of the moment of "collapse", (which just requires agreement by scientists) is as important as the difference between "redundancy" and 'collapse": being the difference between an unknown inevitable outcome of a singular state and a known or reported( by man or machine) outcome of a singular state. That is prior to and post receipt of information. whereas the "collapse" when argument, here, is about what receivers will be designated, by agreement, as switching the physics model that is applicable.

Never, it is I suppose my bet, though I am not sure what Bayesian prior estimate to put on it ;-) As I see it quantum mechanics is of a physical nature that will always fail to conform to the brain's processing of reality. We would need a quantum brain! I might amend never once in the future we have cyber-neural connection (brains becoming a major set of hubs on the internet) and with that we start connecting quantum computers to brains.

Would I prefer that people stop wasting time on quantum interpretations? No not really, and some of them are useful. Even Penrose's interpretation, which is related to the Montevideo interpretation, is useful in some ways. Also, the more people spend on quantum interpretations that takes competitors off the game of doing real physics.

Lawrence,

what is the game of doing real physics?

Dear Georgina,

There must only be one real observable Universe. The question is whether reality is simple and self evident, or if reality is complex, elusive, and only scientifically verifiable. I have proven without a doubt that The real Universe must consist only of one unified visible infinite physical surface occurring in one infinite dimension, that am always illuminated by infinite non-surface light.

Your unrealistic considering of my truth being inappropriate does not alter it. It confirms it dear.

Joe Fisher, Realist

In classical terms, the difference between "redundancy" and "collapse", as you put it, would be, I suppose, the same as the difference between probabilities and statistics, with the latter computed from accumulated datasets. It seems to me that the "accumulated datasets", whether from experiments we consider to be "quantum" or not, are very close to objective, indeed for most physicists such datasets would be taken to be objective, insofar as everyone would see the same numbers on the screen as they scrolled through a dataset. Indeed, a classical collection of datasets is only distinguishable from a quantum collection of datasets by paying close attention (to what joint probability distributions can be constructed, as a particular example).

As you put it, only with provocations, putting the macroscopic numbers of degrees of freedom of "detectors" in the way of a prepared quantum state, does redundancy become collapse (although I think philosophers might phrase the same idea as potential becoming actual).

Lawrence - a very good summary. In my view, many people aren't yet willing to take conceptual steps that were made necessary by QM almost a century ago. Genuinely new models of reality are still too easily dismissed as "new age nonsense". It's become almost a political divide, and obsolete concepts like "an independently existing physical reality" have become non-negotiable articles of faith.

We'll know we're once again making progress when articles about QM aren't full of words like "bizarre", "weird", and "spooky".

Joe, I made it perfectly clear that it is your inconsiderate tedious behaviour that is inappropriate.

Why not add convincing arguments and research, and reconsideration of the replies you have given on your essay page, where it would be appropriate. Some suggestions: Surfaces are not one dimensional. I would be interested to know more about the infinite eye you mentioned and where the eyes of bacteria are located.