Insights Interview with Astrophysicist: Adam Becker - Comments

[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!

 

[vanhees71]

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.

QT=Quantum Theory, of which QFT is one realization to describe the electromagnetic interaction in terms of charged particles and the em. field (both quantized quantum fields in the first-principle level of description).

According to QT (and thus also of course QFT) there's nothing else than probabilities. If an observable is not determined through preparation, then it's value is indetermined, and you can only know probabilities for the outcome of measurements of this observable. To test the theory you have to perform experiments on a sufficiently large ensemble to gain enough statistics for the aimed level of statistical significance.

 

[RUTA]

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!

You are espousing a variant of the Copenhagen interpretation here. Did you read the book?

 

[vanhees71]

This is no Copenhagen this is the Minimal Statistical Interpretation, i.e., in my understanding there's no quantum-classical cut (classical theory is a valid approximation to QT due to the sufficiency of coarse-grained observables for macroscopic properties and decoherence) as seems to be the main point of all flavors of the Copenhagen interpretation. As well there's no collapse due to measurement, which is part of some flavors of the Copenhagen Interpretation.

I've not read the book yet. I've to get it first and then (more difficult) also find the time!

 

[RUTA]

In Chap 12 Adam does mention retrocausality in passing. He talks about it dynamically, i.e., future outcomes sending information into the past, which is in the early spirit of some adherents, but Aharonov, Price, Wharton, and Cramer have all dismissed this pseudo-time-evolved narrative story at some point (to me personally or in print). As I said earlier, given access to the block universe for explanatory purposes, there's no reason to introduce pseudo-time-evolved explanation, it's superfluous.

 

[atyy]

You are espousing a variant of the Copenhagen interpretation here. Did you read the book?

This is no Copenhagen this is the Minimal Statistical Interpretation, i.e., in my understanding there's no quantum-classical cut (classical theory is a valid approximation to QT due to the sufficiency of coarse-grained observables for macroscopic properties and decoherence) as seems to be the main point of all flavors of the Copenhagen interpretation. As well there's no collapse due to measurement, which is part of some flavors of the Copenhagen Interpretation.

I've not read the book yet. I've to get it first and then (more difficult) also find the time!

@RUTA, as you can see from vanhees71's quote, he is indeed not espousing any legitimate variant of Copenhagen, since it has no cut. It is simply not valid quantum mechanics (basically it is a variant of Ballentine's erroneous interpretation).

 

[RUTA]

@RUTA, as you can see from vanhees71's quote, he is indeed not espousing any legitimate variant of Copenhagen, since it has no cut. It is simply not valid quantum mechanics (basically it is a variant of Ballentine's erroneous interpretation).

Wow, yes, I totally misread his post #108. He's not claiming there is no Copenhagen interpretation, he's simply claiming HIS interpretation isn't Copenhagen and then explaining why. I'm too tired to read critically today :-) I'll delete my last post. Thnx, atty.

 

[RUTA]

I finished the appendix where Adam showed how dBB, MWI, and GRW explain Wheeler’s delayed choice experiment done with an interferometer. The delayed choice was simply to insert the second beam splitter (BS) or not after the photon has passed through the first BS. The explanation is trivially dynamical for these interpretations in this experiment. In order to challenge these dynamical interpretations, you need an experiment like the one shown in Sci Am (below). In that experiment you can choose to insert a lens between photons scattered off electrons passing through a twin slit thereby destroying electron which-way info. If you choose not to insert the lens, the scattered photons carry which-way info on the electron to the photon detector. The electrons make an interference pattern when the lens is inserted and a particle pattern when the lens is not inserted. The lens can be inserted after the electrons have already hit their detector (as in the Kim experiment, below). In the Kim experiment, one could easily say the pilot wave takes info from the first photon (“electron” counterpart) to the second photon (“scattered photon” counterpart) to make sure it goes to the correct detector. But, if a human agent is deciding whether or not to place a lens in front of the scattered photon, as in the Sci Am experiment, then dBB would have to either say the pilot wave is influencing the decisions of the human agent, or that the pilot wave is retrocausal from the lens to the electron.

 

[vanhees71]

In Chap 12 Adam does mention retrocausality in passing. He talks about it dynamically, i.e., future outcomes sending information into the past, which is in the early spirit of some adherents, but Aharonov, Price, Wharton, and Cramer have all dismissed this pseudo-time-evolved narrative story at some point (to me personally or in print). As I said earlier, given access to the block universe for explanatory purposes, there's no reason to introduce pseudo-time-evolved explanation, it's superfluous.

Well, I've not read the book (I've ordered the paper back edition arriving end of May), and it might be unfair against the author to discuss about what's claimed to be in that book in a forum, but if he claims that standard QT implies retrocausality, he's utterly wrong. By the very construction of local microcausal relativistic QFT there cannot be any retrocausality by construction, and so far nothing ever observed hints in this direction!

 

[vanhees71]

@RUTA, as you can see from vanhees71's quote, he is indeed not espousing any legitimate variant of Copenhagen, since it has no cut. It is simply not valid quantum mechanics (basically it is a variant of Ballentine's erroneous interpretation).

It's your claim that the Minimal Interpretation is errorneous. By repeating this claim, it doesn't become true! The minimal interpretation is all that you need to confront the theory with experiments (at least those realized up to today), and the theory stands all tests. Anything going beyond the minimal interpretation enters the realm of personal world views and thus is not testable by observation and thus is not part of physics but maybe religion. Not that religious believes are unimportant for individuals, but for sure they are not in the realm of science and the part of humane experience described by it.

 

[atyy]

It's your claim that the Minimal Interpretation is errorneous. By repeating this claim, it doesn't become true! The minimal interpretation is all that you need to confront the theory with experiments (at least those realized up to today), and the theory stands all tests. Anything going beyond the minimal interpretation enters the realm of personal world views and thus is not testable by observation and thus is not part of physics but maybe religion. Not that religious believes are unimportant for individuals, but for sure they are not in the realm of science and the part of humane experience described by it.

I do not agree, and neither do standard texts like Landau & Lifshitz or Weinberg.

 

[RUTA]

Well, I've not read the book (I've ordered the paper back edition arriving end of May), and it might be unfair against the author to discuss about what's claimed to be in that book in a forum, but if he claims that standard QT implies retrocausality, he's utterly wrong. By the very construction of local microcausal relativistic QFT there cannot be any retrocausality by construction, and so far nothing ever observed hints in this direction!

Well if you want a causal account of the experiment shown in the Sci Am article, then either the electron hitting the screen causes the agent to insert or not insert the lens (forward causality) or the agent’s decision to insert or not insert the lens causes the electron to hit the screen in the correct place (retrocausality). One might deny that the Sci Am experimental prediction will be seen because a human is making the decision (unlike the Kim et al experiment where beam splitters “make the decision”). QM doesn’t make different predictions based on conscious versus nonconscious intervention so if you believe that, you would be claiming QM (and QFT by extension) is wrong. Hardy proposed an experiment to explore this possibility https://arxiv.org/pdf/1705.04620.pdf

 

[martinbn]

... It is simply not valid quantum mechanics (basically it is a variant of Ballentine's erroneous interpretation).

How can an interpretation be erroneous?! May be you mean that it is not complete in some sense because it doesn't address some questions?

 

[RUTA]

It's your claim that the Minimal Interpretation is errorneous. By repeating this claim, it doesn't become true! The minimal interpretation is all that you need to confront the theory with experiments (at least those realized up to today), and the theory stands all tests. Anything going beyond the minimal interpretation enters the realm of personal world views and thus is not testable by observation and thus is not part of physics but maybe religion. Not that religious believes are unimportant for individuals, but for sure they are not in the realm of science and the part of humane experience described by it.

You’ll have to read the book. Adam presents many arguments against physics as whole adopting such an attitude. Once you’ve read his arguments, get back to us as to why you think they’re wrong.

 

[atyy]

How can an interpretation be erroneous?! May be you mean that it is not complete in some sense because it doesn't address some questions?

It is erroneous because it is self-contradictory. vanhees71 uses a cut, yet he says there is no cut.

Also, he claims to have a solution to the measurement problem that involves neither hidden variables nor MWI, only coarse graining. This is basically a variant of "decoherence solves the measurement problem", which is an error.

And yes, it is an argument from authority - but there is a reason that the standard texts like Landau and Lifshitz or Weinberg use a Copenhagen-like interpretation.

 

[martinbn]

(basically it is a variant of Ballentine's erroneous interpretation).

It is erroneous because it is self-contradictory. vanhees71 uses a cut, yet he says there is no cut.

I wasn't aware that Ballentine and vanhees71 are the same person!