#QuantumEntanglement #nobelprize #BrianGreeneGreene is usually a good explainer, but this does not explain the award well.
The 2022 Nobel Prize in Physics has been awarded to Alain Aspect, John Clauser and Anton Zeilinger for their groundbreaking work in Quantum Entanglement. Here is a brief visual summary of the essential physics.
z He spends the first couple of minutes arguing that Newtonian mechanics is deterministic, white quantum mechanics is not. I dont think this has anything to do with the Bell test work.
At 4:50, he says that a measurement on one particle can have an instantaneous effect on a distant particle. This is false. Any experimental proof of this would have immediate Nobel prizes.
He says that Einstein wrote a 1935 paper arguing that QM cannot be the whole story. And this Nobel prize winning work addresses that. But Greene does not explain whether the work proved Einstein right or wrong.
Einstein implied that he preferred a local hidden variable theory. The Bell test experiments prove that impossible, so they prove Einstein wrong. Greene says Einstein also wanted a non-probabilistic theory, although that is not so clear from the paper.
I guess Greene is trying to say that Einstein rejected mainstream thinking in 1935, and this prize is for work showing that the mainstream thinking was correct.
But dozens of Nobel prizes have been given for quantum mechanics, so why give another one now?
Greene answer seems to be that the prize work proved action-at-a-distance. It does not.
Dear Roger,
ReplyDelete> "He says that Einstein wrote a 1935 paper arguing that QM cannot be the whole story."
The history is much more complicated than that! What Einstein thought and said was that QM is *incomplete*. (Greene in his presentation uses the word "incomplete", as also "provisional", while describing Einstein's view of QM. Which, IMO, is a correct representation of Einstein's position.)
As to this *conclusion* itself, IMO, it is correct (in the sense, the mainstream QM sure *is* incomplete), but the fact of the matter is, Einstein had reached this *right* conclusion for a *wrong* set of reasons! That's one of the complicated parts of the history...
> "And this Nobel prize winning work addresses that."
Nope, it doesn't.
What the Nobel-winning work addresses is Bell's theorem. What the theorem in turn concerns itself with are (a) the implications given by a class of wrong theories, vis-a-vis (b) similar implications given by QM. What the Nobel-winning work experimentally shows is that the wrong class of theories is wrong. But the work says nothing directly about QM --- let alone about its incompleteness.
In particular, this Nobel-winning work says nothing about the Measurement Problem, or the ontological-physical layer which is required underneath the mathematical postulates of the mainstream QM, so as to make the theory complete. As far as I can gather, this Nobel-winning work never even had *aspired* to begin addressing *those* two things. They began with, and more or less ended with, Bell's theorem. Plain and simple! (They also got the Nobel for that!)
> "Einstein implied that he preferred a local hidden variable theory. The Bell test experiments prove that impossible, so they prove Einstein wrong."
Seems correct to me, but let's hasten to remember that Einstein wasn't around to clarify what *he* meant, when Bell proposed his inequalities.
> "But dozens of Nobel prizes have been given for quantum mechanics, so why give another one now?"
I've touched upon this issue a bit, in my today's post at my blog. (I might revise the post a little here and there, mainly to streamline the presentation, or to make the points a bit clearer. But even in the shape it is in at the moment, I guess, for someone who knows QM, the write-up ought to let him have a good idea of what kind of positions I have taken.)
> "Greene answer seems to be that the prize work proved action-at-a-distance. It does not."
Once again, the issue and various positions about it must necessarily remain hazy, unclear, complicated, or even impossible to pin-down (let alone to analyze), unless people clearly state their ontological views / premises. As to my positions, I've spelt out enough in my ICCTPP paper on iqWaves.
Best,
--Ajit
Yes, Einstein said "incomplete", but it is not clear what he meant, or if he even meant that. A co-author wrote the paper. He appears to mean the theory lacked a system of local hidden variables. Those are impossible, so it is an abuse of the term "incomplete".
ReplyDeleteDear Roger,
ReplyDeleteI've tried to read the EPR paper. But I ran into trouble right in the first few paragraphs, because it was hard mapping what the text says to my understanding of terms like "reality", "theory", "elements of a theory", etc. I felt as if I am being asked to get sucked into a conceptual gray-hole of sorts (being asked first to give up many significant parts of my existing understanding of such terms) if I have to progress through that text. So, it seemed as if a choice had been thrust upon me: Either I enter the gray-hole and immediately finish reading the paper, or I keep my understanding but also allocate a great deal of time to finish reading it. I couldn't give up my understanding, and never could find enough time for this one paper, and so, I chucked it aside. [What I actually did was to click the 'x' button on the browser tab.] ... So, it looks like Bohr had, over the years, managed to rub off some of his Bohr-ness onto Einstein and/or his co-authors too. (Einstein's earlier papers, esp. the 1905 papers, are slightly whimsical in the sense that the arguments aren't always well sorted out, but still, those papers are relatively straight-forward to read.]
So, when it comes to EPR and all, my understanding of Einstein's position concerning this isssue has come exclusively from secondary sources --- historians and biographers (like Pais), pop-sci writers (like Gribbin and Baggott), etc. And of course, Professor Doctor Scott Aaronson's blog. They all must have engaged in this strenuous and time-consuming activity of reading through the EPR paper, and similar original sources, I love to presume. The best resources among such writings, in my limited reading, are those by Dr. Sabine Hossenfelder --- her blog-posts/videos, tweets, and even papers (on Superdeterminism!). For a relevant point, e.g., see this small thread by her: https://twitter.com/skdh/status/1577508143382216704 .
Going by my guesswork concerning what such secondary sources are saying, I have this *feeling*: The EPR progressed their argument (if not based it in its entirety) using the terms, methods, and forms of solution that are specific to the non-relativistic QM (NRQM). I don't feel that EPR they used RQM. At least, I don't see the 4-vector structure of the solution entering into any presentation of EPR's argument (or the Bell inequalities, for that matter).
If the preceding feeling can be elevated to an assumption, then it clarifies a lot. The non-relativistic Hamiltonian involves only the Coulombic potential, and therefore has instantaneous-action-at-a-distance (IAD) built into it. So, whether the issue is the "measurement update" related to a one-particle system, or entanglement in a two-particle system, IAD is an in-built feature --- at least for dynamical variables like position and momentum. Einstein had studied the "classical" Fourier theory. Still, he found the IAD in NRQM to be "spooky". ... One might wonder whether it had also come to frighten him.
I still don't have the time to pick up the EPR paper for a second/third try at reading it. So, I would like to see a secondary source making a presentation of the EPR argument, but in reference to RQM, say, Dirac's theory --- for both one- and two-particle systems.
As to Sabine and her co-authors, if they present not just a scheme at the conceptual level but also a detailed theory (preferably with a simulation that is based on a new PDE of some specific form, one that incorporates their hidden variables in addition to the usual $\Psi$), I would most definitely make sure to read it. Afterall, Sabine does write to be understood. But I guess, I will have to wait.
Once I complete the relativistic extension of the iqWaves approach, I will pick up the issue of the temporal aspects of solutions, including issues like (non-)locality, IAD, etc. I am sure, you all will have to wait. A lot. And, it's only *thereafter* that I will be able to pick up the EPR argument, and the Bell inequalities.
Best,
--Ajit