Interview with Astrophysicist: Adam Becker - Comments

[Peter Morgan]

So do the records of experimental data and setup details have mind independent existence?

I'll mostly defer to vanhees71's account, comment #70. I think of triggers as a definite lossy data compression, but how the data is compressed is presumably decided by some committee, which hopefully has some minds. One could perhaps say that once an experiment has been constructed as an automated object, the data collected can be automated and be mostly independent of mind. Indeed, if human intervention is required to keep an experiment on track because of an error condition that lies outside the automation specified, one would expect that any data during the period during which human intervention was required ought to be discarded (unless, perhaps the human intervention can be formally modeled).
I'll paste in an account I wrote last night to a correspondent, which seems to be a propos:

Consider an Avalanche PhotoDiode, an APD: we set up an exotic state of matter so that the output signal is almost always near zero current, but occasionally it is some obviously non-zero value. Hardware is usually set up to record the time at which a transition from zero to non-zero current happens (we could instead record the current as a 14-bit output from an Analog-to-Digital Converter, an ADC, every nanosecond, say, but the record of current transition times is essentially a very compressed, very lossy record of the same information.) Also of interest in experiments is the dead time, the time it takes the hardware to restore the current to near zero so that another transition can be noticed and the time recorded.
Suppose we have this device. When it's set up in a dark room, there is a low rate of current transitions, called the dark rate; when we enter the room and turn on a dim light, the rate of current transitions changes; when we move around the room, the rate of current transitions changes; when we change the intensity of the light or introduce new lights, the rate of current transitions changes. If we set up some barriers, again the rate of current transitions changes, and again when we move the barriers around. If we set up two or more APDs, we can calculate more elaborate statistics, cross-correlations at the same or at different times.
If we ask what could be causing these events, one answer is that we've set up a ridiculously exotic state of matter, so of course weird stuff will happen. More than that, however, we notice that as we continuously change the conditions of the experiment, the current transition statistics change more-or-less continuously, if we collect enough data. Even though the events are discrete, the statistics change continuously. Historically, elementary physics has said that each current transition is caused by a particle, but more sophisticated physics works with a quantum field, which can be understood to make no claims about what happens outside the APD, nor about details of the APD current, but does discuss the statistics one would observe for a given theoretical model of an APD, and how those statistics would change continuously as we move the lights or the barriers or the APDs around.
For what it's worth, my YouTube video from last February, Quantum Mechanics: Event Thinking, deliberately short at 4'26", presents more-or-less this story.

One additional note, keying into vanhees71's account, is that triggers for large experiments are usually much more elaborate (and can slip into dangerously ad-hoc territory) than just whether one electrical signal transitions from zero to non-zero.

I think it's best not to get too hung up on the Bishop Berkeley problem. Ultimately I can't see that it helps much to be solipsist about the world. Go to the world of extreme positivism for a visit if you like, which I've found occasionally useful as a way to get out of the box, but best to come back. I've been peppering everything I've written on PF with links to my arXiv:1709.06711 (comment #30 has a more up to date version attached) because that's how I think about QM/QFT (for which sorry, I guess) and it's not yet well-known, but for this specific question, I think its mathematical derivation of a random field as a subalgebra of a free quantum field algebra more reconciles a classical perspective and a quantum field perspective than any other math I've seen in the literature (there's a parallel with the de Broglie-Bohm approach, deriving trajectory probabilities from the wave function, but there are also fundamental differences, that I keep to the mathematics of operators acting on Hilbert space as a model for signal analysis, manifest Poincaré invariance is maintained, and I keep to an operational interpretation of the math as far as possible). One significant point, however, is that the philosophy of classical probability has become significantly less settled than it used to be. I'm happy with an instrumental, construct-an-ensemble-and-compute-statistics approach, which I think is what physicists do, but philosophers have worries that I find significant about that approach, and physicists who want to construct a model for the whole observable universe obviously can't construct an ensemble (also, if we take away the background Minkowski space, constructing an ensemble becomes quite fraught, AFAICT —amongst other worries, of course).

 

[Lord Jestocost]

So do the records of experimental data and setup details have mind independent existence?

You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”. You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.

From an instrumentalist' point of view, such questions are idle ones. "In science we study the linkage of pointer readings with pointer readings." (Arthur Stanley Eddington). That’s all. The confusion begins when one tries on base of a schedule of pointer readings to draw conclusions as to the nature of “NATURE”.

Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.

 

[AlexCaledin]

 

[RUTA]

You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”. You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.

From an instrumentalist' point of view, such questions are idle ones. "In science we study the linkage of pointer readings with pointer readings." (Arthur Stanley Eddington). That’s all. The confusion begins when one tries on base of a schedule of pointer readings to draw conclusions as to the nature of “NATURE”.

Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.

I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.

 

[zonde]

You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”.

Sure

You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.

Why should physics prove anything?

Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.

Science requires two things to do it. First, you have to have creative thinking to come up with possible explanations of phenomena. And second, you have to have critical thinking to throw away useless explanations.
"Great liberation of thought" is good for creative thinking, but if you loose the critical thinking part as a result of this liberation ... well, it's just not going to work.

 

[vanhees71]

Indeed. Even the most appealing creative thought has to be confronted with observations and accurate measurements. If you cannot make contact to observables, it's a nice mathematical idea at best or just philosophical gibberish at worst. If your predictions are clearly countered by observation, it's a physical theory that's wrong and needs to be modified (at best) or abandoned (at worst)! As all natural sciences physics after all is an empirical science.

 

[Lord Jestocost]

I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.

Sir Arthur Stanley Eddington in "The Nature of the Physical World“:

"Scientific instincts warn me that any attempt to answer the question “What is real?” in a broader sense than that adopted for domestic purposes in science, is likely to lead to a floundering among vain words and high-sounding epithets."

 

[Peter Morgan]

Indeed. Even the most appealing creative thought has to be confronted with observations and accurate measurements. If you cannot make contact to observables, it's a nice mathematical idea at best or just philosophical gibberish at worst. If your predictions are clearly countered by observation, it's a physical theory that's wrong and needs to be modified (at best) or abandoned (at worst)! As all natural sciences physics after all is an empirical science.

vanhees71, I can't see which comment you're referring to here. I understand if you might not want to use QUOTE, but it would help a lot if you would cite a comment number. TBH, I'm saying this because I've been unsure what or who you've been referring to a number of times, not just because of this one comment. Sorry! I won't say this again until I forget that I said it.

 

[RUTA]

Sir Arthur Stanley Eddington in "The Nature of the Physical World“:

"Scientific instincts warn me that any attempt to answer the question “What is real?” in a broader sense than that adopted for domestic purposes in science, is likely to lead to a floundering among vain words and high-sounding epithets."

Did you read Adam's book?

 

[Peter Morgan]

Did you read Adam's book?

I look forward to reading a review from you, RUTA. Having been to the talk Adam gave last night in New York, I'm not very enthusiastic. The last time I remember someone landing hard on a conversation at a foundations of physics conference with "Copenhagen says X, so everything you're saying is nonsense", was in the early 90's, and my sense is that physicists now more often fall back on decoherence (notwithstanding that the last mile from a mixed state to actual events is glossed), an interpretation which Adam didn't mention in his talk (I suppose because many philosophers would be loath to call decoherence an interpretation at all). Furthermore, I just read that Feyerabend in 1962 said (cited in arXiv:1509.09278, page 43)

. . . many physicists are very practical people and not very fond of philosophy. This being the case, they will take for granted and not further investigate those philosophical ideas which they have learned in their youth and which by now seem to them, and indeed to the whole community of practicing scientists, to be the expression of physical common sense. In most cases these ideas are part of the Copenhagen Interpretation.
A second reason for the persistence of the creed of complementarity in the face of decisive objections is to be found in the vagueness of the main principles of this creed. This vagueness allows the defendants to take care of objections by development rather than a reformulation, a procedure which will of course create the impression that the correct answer has been there all the time and that it was overlooked by the critic. Bohr's followers, and also Bohr himself, have made full use of this possibility even in cases where the necessity of a reformulation was clearly indicated. Their attitude has very often been one of people who have the task to clear up the misunderstandings of their opponents rather than to admit their own mistakes.

which seems a clear statement, 56 years ago, of what seemed to be a large part of Adam's argument for why Copenhagen is still given lip service today.
Adam at one point said that he hopes to give his talk to physics departments, but TBH with nothing at all said about QFT (is there anything about QFT in the book?), and decoherence unmentioned, I can't see physicists taking him seriously. One high point of going to Adam's talk was that I talked to several Masters and PhD students and postdocs, all of whom seemed quite knowledgeable about and willing to talk about the interpretation of QFT.

 

[RUTA]

I'm in Adam's chapter 6 on Bohm and Everett. I haven't seen anything about QFT mentioned in the other reviews and he has made little mention of it so far in his book, so I doubt he talks about interpretations of QFT. We offer an interpretation of QFT in chapter 5 of our book and that chapter opens with the following:

As for progress in this area, Healey notes, “no consensus has yet emerged, even on how to interpret the theory of a free, quantized, real scalar field” [Healey,
2007, p. 203]. And, “There is no agreement as to what object or objects a quantum field theory purports to describe, let alone what their basic properties would
be” [Healey, 2007, p. 221].

Foundations of physics (FoP) doesn't spend much time on this subject. FoP's attitude is that the weird/fun stuff is in QM, the only mysteries about QFT are technical, e.g., Haag's theorem, so FoP deals almost exclusively with QM. In my 24 years of attending FoP conferences and talks, I don't remember even one presentation on QFT issues. I'm very interested in your interpretation of QFT, as you know, because it looks to fill in technical gaps with my interpretation of QFT. With your help, I'll figure it out :-)

In the first 5 chapters, Adam has focused on the history of the Copenhagen interpretation (in its many variations) and why we're stuck with it now. His coverage of interpretational issues of QM has been sparse to this point. Based on reviews I've read, I'm assuming he'll plug those holes in part 3 of the book.

 

[Peter Morgan]

Foundations of physics (FoP) doesn't spend much time on this subject. FoP's attitude is that the weird/fun stuff is in QM, the only mysteries about QFT are technical, e.g., Haag's theorem, so FoP deals almost exclusively with QM. In my 24 years of attending FoP conferences and talks, I don't remember even one presentation on QFT issues. I'm very interested in your interpretation of QFT, as you know, because it looks to fill in technical gaps with my interpretation of QFT.

Different circles! I think you're right, although I haven't been to a Foundations of physics conference, $lo$, the last ten years. Perhaps it's more the philosophers who have taken up the philosophy of QFT, and there are several mathematicians who have tried to make sense of the mathematics of renormalization/interacting QFT with what seem almost philosophical motivations. I filter out a majority of non-QFT foundations these days, so it seems quite the opposite way round. QFT changes the game totally, IMO, makes everything much easier, partly because there are already fields, so it's fields/waves duality, which I think is easier to live with, but of course I have to convince anyone of that.

 

[RUTA]

I just finished Adam's analysis of the Bell inequality via a roulette wheel. I've heard this before in a different context, but it's a very nice way to introduce the Bell inequality to laymen. His claim afterwards is that only one of three logical possibilities exists: nonlocality, superdeterminism, or QM is wrong. Most people accept the experimental results vindicating QM, so few if any argue for the third option anymore (it was more common when I started working on this in 1994). I'm assuming he believes retrocausality falls into the SD camp? It's semantics, but I'd disagree with that since the "common cause" resides in both the future and past. I wouldn't say that any of the three options applies to the ontology of Relational Blockworld (RBW) where explanation is adynamical and QM is certainly correct. Therein, the fundamental ontological element is 4-dim and QM provides a distribution function for these 4D "spacetimesource elements" in the context of a classical block universe. So, we do have "realism" and there are no superluminal signals required in the explanation of the distribution of these real 4D objects in spacetime. I'm not even sure that the concept of nonlocality is relevant when discussing 4D objects (careful, this nonlocality has to do with superluminal signaling, not the locality assumed in differentiable manifolds). Silberstein and I are giving a talk to the foundations group at the Univ of MD next Wed, so I'll solicit their opinions. But, he and I agree that the standard analyses of Bell inequalities tacitly assume dynamism and are meaningless for adynamical explanation. Continuing, there is certainly no SD in RBW because there is no dynamical causation in adynamical explanation. In other words, when Adam claims to have exhausted all logical possibilities for the implications of Bell's inequality, he has failed to consider adynamical explanation.

 

[vanhees71]

vanhees71, I can't see which comment you're referring to here. I understand if you might not want to use QUOTE, but it would help a lot if you would cite a comment number. TBH, I'm saying this because I've been unsure what or who you've been referring to a number of times, not just because of this one comment. Sorry! I won't say this again until I forget that I said it.

I only quote if I refer to a posting not immediately before the posting I'm answering to.

 

[vanhees71]

I just finished Adam's analysis of the Bell inequality via a roulette wheel. I've heard this before in a different context, but it's a very nice way to introduce the Bell inequality to laymen. His claim afterwards is that only one of three logical possibilities exists: nonlocality, superdeterminism, or QM is wrong.

He forgot the third, which is the contemporary solution of this apparent problem, which is local microcausal relativistic QFT. It's local (i.e., fulfilling the linked-cluster principle) and allows for the long-range correlations described by entanglement of parts of quantum systems that are observed at far-distant points. Of course, you have to give up naive collapse interpretations, which introduce an artificial action at a distance, which is in clear contradiction to the very foundations the Standard Model rests upon, namely locality and microcausality. Of course QM is only a non-relativistic approximation of the relativstic QFT and thus becomes wrong when applied to situations where the approximation is invalid.

 

[RUTA]

He forgot the third, which is the contemporary solution of this apparent problem, which is local microcausal relativistic QFT. It's local (i.e., fulfilling the linked-cluster principle) and allows for the long-range correlations described by entanglement of parts of quantum systems that are observed at far-distant points. Of course, you have to give up naive collapse interpretations, which introduce an artificial action at a distance, which is in clear contradiction to the very foundations the Standard Model rests upon, namely locality and microcausality. Of course QM is only a non-relativistic approximation of the relativstic QFT and thus becomes wrong when applied to situations where the approximation is invalid.

That's not true, the formalism maps beautifully onto the experimental set-ups and data. There are many analyses, but one for undergrads that I use in my QM course is attached. There's nothing in the formalism that resolves this issue.

 

[Peter Morgan]

That's not true, the formalism maps beautifully onto the experimental set-ups and data. There are many analyses, but one for undergrads that I use in my QM course is attached. There's nothing in the formalism that resolves this issue.

Quantum theory, being probabilistic, only makes predictions about statistics associated with recorded measurements. As a probabilistic theory, it has nothing to say about individual recorded events, only about their statistics. As a statistical theory, it includes the notion of microcausality, that measurements associated with space-like separated regions commute, but this is consistent with us being able to prepare states in which there are correlations at space-like separation.
I see this as resolving the difference between vanhees71 and yourself, that quantum theory is microcausal as a probabilistic theory, whereas a theory that non-stochastically predicts the precise timings of individual recorded events would appear to have to be either nonlocal or superdeterministic (or some combination thereof: any such model might require infinite information to be predictive if there's any chaos, so I can't see how we could determine what a non-stochastic theory would be, I think we have no honest choice but to say "hypotheses non fingo").

I can see some merits to the paper you attach, but, of course, I'd like something better. In particular, IMO the role played by the incompatibility of the pairs of measurements at each end should be emphasized: if we were to perform only compatible measurements at each end separately, there would be no violation of any Bell inequalities. That there are incompatibilities means that there are time-like dependencies, but between the two measurements at A and between the two measurements at B, not between the ends (that is, if we have two measurements at A and two measurements at B, $[A_i,B_j]=0, [A_1,A_2]\not=0, [B_1,B_2]\not=0$.) And I'd prefer "particles" not to be mentioned at all (instead of the word appearing 34 times): to be trite, for the quantized EM field there's just a wave/field duality. But that's a different paper altogether.

 

[Lord Jestocost]

I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.

As I haven't read the book yet, I don't know Adam Becker's attitude.

 

[Boing3000]

Quantum theory, being probabilistic, only makes predictions about statistics associated with recorded measurements. As a probabilistic theory, it has nothing to say about individual recorded events, only about their statistics.

That is a nice refresher for those who think that quantum theory is a description of reality, instead of just a description of what would happens to "equally prepared state", that is "in a laboratory"

As a statistical theory, it includes the notion of microcausality, that measurements associated with space-like separated regions commute, but this is consistent with us being able to prepare states in which there are correlations at space-like separation.

As a layman, do you know of any resource that will explains how QFT micro-causality is supposed to solve the EPR macro stochastic causality behaviors ?

Also Ruta's point on block -universe "interpretation" seems quite interesting, I'll try to dig into that also...

I see this as resolving the difference between vanhees71 and yourself, that quantum theory is microcausal as a probabilistic theory, whereas a theory that non-stochastically predicts the precise timings of individual recorded events would appear to have to be either nonlocal or superdeterministic (or some combination thereof: any such model might require infinite information to be predictive if there's any chaos, so I can't see how we could determine what a non-stochastic theory would be, I think we have no honest choice but to say "hypotheses non fingo").

Aouch .. Latin hurts more than math On this topic of timing, isn't Bohmian's mechanic supposed to have more predictive power over classical QM ? If some spin value is observed to be X by Alice, isn't the (entangled?) pilot wave time dependency suppose to make more accurate prediction over the entangled value over time (and space) at Bob's end ?

 

[Peter Morgan]

That is a nice refresher for those who think that quantum theory is a description of reality, instead of just a description of what would happens to "equally prepared state", that is "in a laboratory"

What I said, that QM/QFT is a probabilistic theory —which can be understood to model, and hence in appropriate circumstances to predict, statistics of recorded experimental events—, seems to me not inconsistent with quantum theory being "a description of reality". I think of QM/QFT, admittedly loosely, as being as much as we can say about "reality" because to predict individual events in a chaotic world would require more information than I think we can plausibly have access to, perhaps even might require infinite information.

As a layman, do you know of any resource that will explains how QFT micro-causality is supposed to solve the EPR macro stochastic causality behaviors ?

I have a terrible memory, I'm afraid. I retain concepts more-or-less, once I've grokked them, but I too often forget where I learned about them and where the good references are. That said, I don't think of microcausality as solving EPR. Microcausality —that measurements are compatible with and don't change the statistics of other measurements that are at space-like separation— is apparently consistent with experiment, whereas in fact we can set up states in which there are correlations and Bell inequality violations between space-like separated measurements.

On this topic of timing, isn't Bohmian's mechanic supposed to have more predictive power over classical QM ?

I think of Bohmian mechanics more as retrodicting a trajectory, given an individual actual event, if we know (or think we know) the quantum dynamics. That is, if the event is caused by a particle, that particle must have come from somewhere, because that's what particles do. We can massage the quantum dynamics to give us an equation that determines a trajectory when it's given just a single point on that trajectory (it's sometimes cited as a conceptual difficulty for Bohmian mechanics that we don't need to know the velocity as well as the position to determine the trajectory —differently from the case for classical mechanics, that is). BUT, at least in those cases where we do not observe more than one point (not high energy physics, and not a football or anything else large, in other words, but for most low energy experiments, because then the particle is absorbed and doesn't carry on along the same trajectory), that's not a prediction. To claim that de Broglie-Bohm is empirically equivalent to QM, one has to say that de Broglie-Bohm is a probabilistic theory.
Personally, I'm OK with de Broglie-Bohm trajectories for the non-relativistic case, except that, crucially, the math is a mess compared to just using Hilbert spaces. When we use QFT, however, I've not seen de Broglie-Bohm work out well enough. Most physicists just cite the QFT case as a one-line dismissal.

 

[PeterDonis]

how QFT micro-causality is supposed to solve the EPR macro stochastic causality behaviors ?

QFT "micro-causality" means that spacelike separated measurements must commute (i.e., the results must not depend on the order in which they are performed). Bell-inequality violating experiments meet this condition. So I don't see what there is to "solve".

 

[RUTA]

Quantum theory, being probabilistic, only makes predictions about statistics associated with recorded measurements. As a probabilistic theory, it has nothing to say about individual recorded events, only about their statistics. As a statistical theory, it includes the notion of microcausality, that measurements associated with space-like separated regions commute, but this is consistent with us being able to prepare states in which there are correlations at space-like separation.

Thnx for intervening, hopefully this exchange will educate those who are likewise confused :-) The issue isn't with the formalism and it isn't with the data (I hope that isn't what you're implying). The formalism maps beautifully onto the data, as you can see in the paper. The issue is what you appear to brush aside. The statistical data is collected one event (coincidence) at a time (within the 25-ns coincidence window), just like the roulette balls in Adam's analogy. Therefore, any explanation for the correlation in the statistical data should be based on the nature of reality as it pertains to each trial (and it's not accidental coincidences as you can see from the last column of Table 1).

I think we have no honest choice but to say "hypotheses non fingo").

Bring your explanation supra to bear on Adam's roulette wheel analogy and you'll see where it's lacking. That is, you'd be attempting to resolve the mystery by saying, "I have a statistical mathematical formalism that maps onto the statistical data." That answer in no way tells me what is causing the two balls to land in the same color every time the two experimentalists choose the same wheel number, but land in the same color only 25% of the time that the two experimentalists choose a different wheel number. [This is exactly the Mermin analogy, see my QLE explanation, where we expect at least 33% agreement for different wheel numbers in order to account for 100% agreement for same wheel numbers.] Giving up on finding the underlying cause for the experimental correlations is your choice, but that in no way resolves the issue for those of us who haven't given up.

I can see some merits to the paper you attach, but, of course, I'd like something better.

The experiment instantiates a QM violation of a Bell inequality. There is nothing more needed to experimentally confirm the mystery a la Adam's roulette wheels or Mermin's device, unless you believe there is something wrong with QM (Adam's third option). Is that what you're implying?

 

[Peter Morgan]

The experiment instantiates a QM violation of a Bell inequality. There is nothing more needed to experimentally confirm the mystery a la Adam's roulette wheels or Mermin's device, unless you believe there is something wrong with QM (Adam's third option). Is that what you're implying?

It's the theoretical gloss in the paper that I find lacking. I'm confident the experiment as given, using off the shelf components, violates Bell inequalities, and I'm reading you to be saying that your students have done the experiment dozens of times over the years? I asked for Gregor Weihs' raw data at one time and analyzed it in a way that showed him a new feature, though it's not earth-shattering (arXiv:1207.5775, also on my very irregularly maintained blog, https://quantumclassical.blogspot.com/2010/03/modulation-of-random-signal.html — astonishing, for me, to see that that is 8 years ago).
So I don't doubt the weirdness.
I'm by no means saying that others can't tackle classical chaos in sophisticated ways in an attempt to model quantum level systems deterministically, it'd be great if someone could give us a toe-hold on that, but I'm certain I'm not a good enough mathematician to tackle that head on. My only hope would be to notice something serendipitously as a result of being so immersed in the relationship between quantum and random fields, although I think that's probably already given into the urge to address chaos with probability.

 

[RUTA]

Just finished Part II. Chapter 8 is what the Copenhagenists, instrumentalists, operationalists, and positivists among you should read.

He’s advocating for dBB and MWI, not because he necessarily believes those are “right,” but simply because they offer counterexamples to Copenhagen. I didn’t realize Copenhagen was so dogmatic, I thought it was merely instrumentalist, which I have always considered “agnostic.” Adam’s take on instrumentalism is a la positivism and operationalism, both of which strike me as more dogmatic. Physicists who are just not interested in analyzing various interpretations aren’t impeding progress, since their lack of interest means they wouldn’t likely contribute anything meaningful anyway. It’s those who naively believe they don’t even possesses an interpretation themselves and actively dissuade younger physicists from asking those questions. Part II presents an interesting history explaining how the attitudes of Copenhagen, instrumentalism, positivism, and operationalism became so popular among physicists when philosophers have long since dismissed them on intellectual grounds.

 

[atyy]

He’s advocating for dBB and MWI, not because he necessarily believes those are “right,” but simply because they offer counterexamples to Copenhagen. I didn’t realize Copenhagen was so dogmatic, I thought it was merely instrumentalist, which I have always considered “agnostic.”

It depends on whose Copenhagen. I go to both churches without any sense of conflict.

 

[AlexCaledin]

The thing is, everyone naturally has his own wishful thinking! To avoid offending someone's sacred hopes (like materialism or many worlds or Divine Choice), it's necessary to keep certain wise dogmas developed by Niels Bohr and company .

 

[George Jones]

The thing is, everyone naturally has his own wishful thinking! To avoid offending someone's sacred hopes (like materialism or many worlds or Divine Choice), it's necessary to keep certain wise dogmas developed by Niels Bohr and company .

I cannot tell whether this post is tongue-in-cheek or serious.

I didn't know that Niels Bohr developed any wise dogmas. Dogmas, yes.

 

[AlexCaledin]

I cannot tell whether this post is tongue-in-cheek or serious.

I didn't know that Niels Bohr developed any wise dogmas. Dogmas, yes.

- but don't forget, Bohr had Einstein to discuss things with; - and nowadays you only have guys whose Most Sacred Hope is just to attain unto perfect non-existence in the end; - so, to you, Bohr's ideas are of no use of course.

 

[RUTA]

I'm reading Part III and some of the history has surprised me. I got into the game (1994) after the situation in foundations of physics had started to improve, but Aharonov warned me at the time there were perils associated with working in foundations. The hostility of the physics community towards physicists working in foundations was appallingly anti-intellectual. Albert had publications in Phys Rev with Aharonov yet his university would not let him do this work for his PhD thesis. He was told flat out that if he didn't do the problem in QFT they had given him, then he would be dismissed from their program. Work by Bell and even Clauser's experimental work were deemed "junk science." Another thing I didn't know was that Holt had repeated Clauser's experiment and found the Bell inequality was not violated. At that time, there were just the two contradictory results, so it wasn't clear whether QM was right or not. The guys doing these experiments had to beg for lab space and had to borrow or scrounge for equipment. It took Aspect six years to build, conduct and publish his first experiment. When he ask Bell about doing the experiment, Bell refused to talk to him until Aspect assured Bell that he had tenure. Zeh has similar horror stories. I already respected the pioneers in this field for their discoveries, now I respect them as well for their perseverance in the face of such adversity.

 

[George Jones]

some of the history has surprised me

I was surprised to find out how Wheeler treated Everett.

 

[RUTA]

I just finished chapter 11 where Adam defends the various many-worlds views (string theory’s landscapes, inflation’s multiverse, and Everett’s Many-Worlds Interpretation, MWI). He admits MWI has a problem with the meaning of probability, but dismisses it as something to be solved in the future. I’m less optimistic, since the idea has been in vogue (in FoP anyway) for many years and yet the problem persists. For example, it can’t be simply that the branches split with a “frequentist interpretation of probability,” as Adam illustrates with the Schrodinger Cat in a 25% dead — 75% alive probability when there are only two possible outcomes. Another problem with a frequentist-splitting interpretation would be that many branches would not in fact obtain empirical evidence for the correct splitting probabilities (as seen from a global perspective “outside” all the branches), as Adrian Kent pointed out years ago. So, how do we know we’re in a branch where our experiments actually reflect the correct probabilities? Finally, Adam defends these many-worlds views against accusations that they’re unscientific because they’re unverifiable. He properly points out that all scientific theories are unverifiable in the sense of Popper, e.g., deviations in Uranus’s predicted orbit led to the discovery of Neptune, not the overthrow of Newtonian gravity. Later, deviations in the orbit of Mercury did lead to Newtonian gravity being “falsified,” i.e., replaced by a more accurate theory (GR). Here I think Adam’s defense is strained at best. There is a huge difference b/w Newtonian gravity not being falsified by a single apparently discordant measurement (Uranus’s orbit) and the fact that EVERY POSSIBLE measurement outcome is compatible with a theory. To claim the former case is equivalent to the latter is an egregious misrepresentation of the objection of unfalsifiability. To paraphrase one opponent of such views, “Does a theory that predicts everything explain anything?” On to chapter 12!

 

[vanhees71]

That's not true, the formalism maps beautifully onto the experimental set-ups and data. There are many analyses, but one for undergrads that I use in my QM course is attached. There's nothing in the formalism that resolves this issue.

I don't understand, what you think is "not true" in my previous statement. Your nice undergrad-lab experiment described in your paper does not prove quantum nonlocality, or do you claim that its outcome cannot be described by QED? What your experiment indeed demonstrates (as far as I can see from glancing over the paper) are the long-ranged correlations between entangled parts of a single quantum system, which is not contradicting locality of the interactions. QED, as any QT, allows to describe entanglement without violating locality by construction, and also the linked-cluster theorem holds true. It is just careless use of the word "non-locality" instead of "long-ranged correlations" you find very often in the literature, and that is bound to confuse your students rather than helping them to understand that the beautiful Bell-test experiments with photons done in the last 2-3 decades demonstrate that entanglement really means what QT predicts, i.e., the incompatibility of the probabilistic predictions of QT about ensembles with any classical-statistical local deterministic hidden-variable model a la Bell.

 

[RUTA]

I don't understand, what you think is "not true" in my previous statement. Your nice undergrad-lab experiment described in your paper does not prove quantum nonlocality, or do you claim that its outcome cannot be described by QED? What your experiment indeed demonstrates (as far as I can see from glancing over the paper) are the long-ranged correlations between entangled parts of a single quantum system, which is not contradicting locality of the interactions. QED, as any QT, allows to describe entanglement without violating locality by construction, and also the linked-cluster theorem holds true. It is just careless use of the word "non-locality" instead of "long-ranged correlations" you find very often in the literature, and that is bound to confuse your students rather than helping them to understand that the beautiful Bell-test experiments with photons done in the last 2-3 decades demonstrate that entanglement really means what QT predicts, i.e., the incompatibility of the probabilistic predictions of QT about ensembles with any classical-statistical local deterministic hidden-variable model a la Bell.

The formalism for the experimental outcomes is in the paper. That's not the issue. The question is, what is the nature of reality such that those correlations obtain? Simply saying the formalism maps onto the outcomes in no way tells me WHY those correlations obtain, only that you found a formalism that maps onto to them. Again, go to Adam's roulette wheel analogy and the formalism of the paper would equally map to those outcomes. How can that be?

 

[zonde]

QED, as any QT, allows to describe entanglement without violating locality by construction, and also the linked-cluster theorem holds true. It is just careless use of the word "non-locality" instead of "long-ranged correlations" you find very often in the literature

QT gives statistical description of entanglement. But the point of Bell theorem is that there is a testable difference between "long-ranged correlations" realized by local physical mechanisms and non-local physical mechanisms when you analyze the data on the event by event basis.
In that sense there is no difference between QT and QED. QED gives its predictions on statistical level and gives no handle for event by event analysis. I suppose that this not so obvious because QFT speaks about "fields" just like electromagnetic field that is considered physical. But the "field" of QFT is not physical. It's statistical.

 

[vanhees71]

The formalism for the experimental outcomes is in the paper. That's not the issue. The question is, what is the nature of reality such that those correlations obtain? Simply saying the formalism maps onto the outcomes in no way tells me WHY those correlations obtain, only that you found a formalism that maps onto to them. Again, go to Adam's roulette wheel analogy and the formalism of the paper would equally map to those outcomes. How can that be?

Well, as an experimentalist you should be much less worried about what's reality than the theoreticians, because it's you who defines what reality is! You set up your devices to produce the entangled bi-photon states and the various optical devices and detectors to observe them. What's real is what your detectors show. The theory (in this case QED, simplifying the devices to an effective description which is more or less the same as in classical electrodynamics (quantum optics of optical devices is mostly the hemiclassical approximation, i.e., matter treated phenomenologically in terms of response functions/susceptibilities), except for the detection process of photons itself, which usually is some kind of photoelectric effect (which can be almost always be treated semiclassically, i.e., assuming classical em. fields but quantized electrons). All this is not reality but an (effective) quantum-field theoretical description for the statistical outcome of your detector clicks, and what's real are the clicks, not the theorists' field operators and state operators!