Thursday, May 30, 2019

Quantum mechanics: Still mysterious after all these years

Last week I was in Barcelona, Spain, where I visited the Center for Contemporary Culture (CCCB). I didn’t know until I arrived that they currently have an exhibition on quantum mechanics. I have found the exhibition to be very interesting, and – thinking you would find it interesting too! – compiled the below video.

Since I didn't have my video camera with me, it is made of footage provided by the CCCB and some recordings that a friendly lady from the Spanish TV made on her phone. Enjoy!



Update May 31st: Now with Italian and German subtitles. Click on CC in the YouTube toolbar. Chose language in settings/gear icon.

28 comments:

  1. You haven't any chance to be convinced that there is any randomness, have you?

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    Replies
    1. If physical states are convex sets, the theory of the dimensions of such is that for a convex set with dimension p the dual with dimension q obeys

      1/p + 1/q = 1

      These define L^p sets, and for p = 2 it is the case then that q = 2. For reasons I will not go into this is associated with a duality between quantum mechanics, that defines probabilities and the Born rule with the square of amplitudes, and general relativity that employs the metric with ds^2 = sum g_{ab}dx^adx^b. Standard probability theory is a straight sum of probabilities and is thus an L^1 theory. The dual is then an L^∞. This is interpreted as a purely deterministic theory, which can mean anything from Newtonian mechanics to deterministic Turing machines. I take the L^2 theories as central. The L^1 and L^∞ are a bit nuanced. If you hold to Bohr's Copenhagen interpretation, there is then a classical world and the occurrence of quantum measurements are stochastic. Decoherence does illustrate that outcomes occur as a a purely classical theory, so are in effect L^1. If one holds that classical mechanics is an approximation and "not real" then this involves a ψ-ontic interpretation. From a phenomenological perspective it seems that classical mechanics and pure stochasticity are best treated as real

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    2. I suppose that those who believe randomness does not exist could sue QRNG hardware manufacturers for false advertising. Typical product advertisement:

      "The development of our family of Quantum Random Number Generator has been optimized to provide more speed, scalability and true randomness at a fraction of the cost of other devices in the market. Our innovative and patented solution uses a purely quantum phenomenon – quantum tunneling – to generate truly random numbers."

      Delete
    3. Randomness is a strange concept. Given a binary system there can exist 2^n different symbol strings of length n. Now, those that are the most random are not compressible by an algorithm. However, Kolmogorov showed that randomness can only be defined in a finite set, and for our set of random strings we can't know for sure which are really "random." We have a big of a conundrum similar to Gödel's theorem. Zurek showed there is no procedure for finding the optical data compression algorithm. It is a universal Turing machine problem of needing a universal compression system. Chaitin showed there is not way to define a general algorithm to find the Halting probability for any set of binary strings of length n.

      So whether QM is or is not absolutely and purely random probably can't be proven. I will say if QM is not purely random it may be the most random-like thing in the world.

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  2. Hi, Sabine.

    Have you had time to read the IMO wonderful book of Lee Smolin: "Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum"? If it was the case, what did you think about it?

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    Replies
    1. Samu,

      No, but I am almost done with Philip Ball's "Beyond Weird", and then I'll write a review, and then Lee's is up next.

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    2. Sabine, I'd appreciate a lot a review post from your side about Lee's book once you can read it please.

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    3. Sabine, do you think this recent paper: https://www.nature.com/articles/s41586-019-1287-z aport something in the debate of Lee's book? What's your opinion about this interesting paper?

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    4. No, it doesn't support Lee's ideas, and I don't find it particularly interesting, sorry.

      Delete
    5. I thought it was a point in favor of scientific realism. I guess I was wrong (some people affirm this anyway, that's why I asked you). Thank you for your response.

      Delete
  3. As far as I know, finding problems that a quantum computer can solve more efficiently than a classical one is still a field of research. Not solving them, just finding them.

    'Vastly' is just a dream, in the foreseeable future.

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  4. Sabine said: How much of our life is really just due to random chance? If you could find out, would you want to find out?

    Yes. I reconciled myself to random chance when I was a teen, when I converted from Christianity to atheism. Unless I receive evidence to the contrary, I assume that we exist on an inconsequential speck of dust in an uncaring universe. I'm inclined to assume that "life" is merely an emergent property of inanimate matter. In a best-case scenario, life is "special" only in the sense that it's a rare emergent property. In the realm of consciousness, if we aren't free agents with free will, I'm willing to settle for self-serving illusions. If we're a simulation, I'm inclined to think that the designer is sadistic. :-)

    I'm not saying this because I'm inclined toward nihilism. Truth be told, I would very much prefer an afterlife where we move on to bigger and better things. You mention "mystery." I feel like we're trapped in Plato's cave, looking at shadows on a wall, and I'd like to believe that we can escape from that cave in an afterlife. But that's wishful thinking.

    As far as I know, our ape cousins don't feel bad about their limitations or that they can't fathom the mysteries. It's bad enough that humans can't solve all the mysteries. We also fret over the unknown unknowns, or as US Secretary of Defense Donald Rumsfeld said, "There are unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones."

    Even though I assume I'm an emergent property of inanimate matter due to random chance, soon to return to an inanimate state, I would still want to find out, for certain, that this is the case. Isn't that funny? Is that healthy scientific skepticism or is it really just a glimmer of hope that my assumption is wrong?

    Speaking of random chance, I'd like to dedicate an ABBA song to the uncaring universe:

    If you change your mind, I'm the first in line
    Honey I'm still free, take a chance on me
    If you need me, let me know, gonna be around
    If you've got no place to go, if you're feeling down
    If you're all alone when the pretty birds have flown
    Honey I'm still free, take a chance on me
    Gonna do my very best and it ain't no lie
    If you put me to the test, if you let me try

    Take a chance on me
    (That's all I ask of you honey)
    Take a chance on me

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    1. “If we're a simulation, I'm inclined to think that the designer is sadistic.”
      Not necessarily, if the designer of the physics engine himself does not know how his piece of art, our world, will evolve. If a tiny random element like QM measurements is included, then there is surprise, real Shannon information, good and bad stuff will happen, no way of knowing in advance.
      Of course, if he runs the simulation a second time with the very same seed (*) and initial values, just to watch the bad scenes, the very same suffering again, then I also would call him sadistic and he really needs to seek professional help.
      But let us benevolently assume this is the first run and he is just a curious creator and cannot, or better does not want to interfere with the evolution of our world (**), because he wants many of the emerging creatures to become rational beings, scientists, also trying to decode the (unchanging) physical laws, that determine the evolution of their world. But even in this case just watching his creation, makes him a kind of voyeur and he should better go and start to live his own life. (***)


      -------------------
      (*) for the pseudo random number generator, which is used to decide which outcome to pick in QM measurements in our world.
      (**) a world without supernatural miracles, just a handful of curiously finetuned parameters.
      (***) but please do not stop the simulation – thanks and we guess you care, but you cannot take care - “shit just happens”.

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  5. Hi, SABINE !
    Thanks so much for the video.
    It was really cool.
    I watched it a number of times as I may not be able to be in Barcelona before the end of December.
    That may be for the best
    as I tend to spend
    more time than
    I can afford.
    - when the exhibit is good.

    I agree with you that attempts to 'mix' art with science
    (usually) do not end well.
    However, in searching
    for 'balance' in the Universe
    or in one's personal life.
    Science and Art often can be
    complimentary.
    You have certainly shown this.

    - will comment later if time allows. ( have some things to say
    about the term/ concept
    'random' (ness).

    All Love,
    Oh, and the background music in the video was Very cool.


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  6. The strange elements of QM are not due to stochasticity. As I illustrated to Eusa convex hulls that are L^p are dual to those that are L^q with 1/p + 1/q = 1. A convex hull or shape with X is dual to another Y with

    Y = {y| c + x·y ≥ 0 ∀y ∈ Y}.

    The case of p = ½ is with quantum mechanics and its dual may then be spacetime physics. The above definition of the convex set or hull can pertain to scalar tensor theories L = √g φR where the √g cancels the Jacobian determinant in coordinate transformations for invariance and the φ is a scalar field and R is spacetime curvature. This is a product term that serves well to define the above duality between convex sets. In fact conformal gravitation is this dual field theory with the conformal factor defined by such fields. For quantum gravitation this may be a duality theory of discrete polytopes for Weyl chambers.

    What about the p = 1 and q = ∞ case? This is the more difficult in a way. We normally do not think of classical mechanics as a theory with an integration measure over classical states. In fact we only have the observables {p, q} or similar conjugate variables and no reference to states as such. Similarly for deterministic systems such as a Turing machine or Conway's Game of Life. This is a way of thinking of the L^∞. The p = 1 case is straight up probability theory, where there is no underlying assumption of determinism. With the outcomes of quantum measurements it can be said the lack of any causal process in such outcomes leads to pure stochasticity. This is why the use of a radioactive substance in a random number generator makes perfect sense. I suggested this in fact to somebody who worked on codes and cyphers at Sandia National Labs many years ago. Classically systems such as the roll of dice or the outcome of the Roulette wheel are purely stochastic FAPP. The role of such systems gained importance after Pascal worked on the probabilities with the Roulette wheel in the 17th century.

    Stochasticity does nothing to really help argument for free will. A meat puppet that follows many determnistic rules has all the freedom another might have that acts according to purely random outcomes.

    The oddity with quantum mechanics is not so much stochastic processes. We are really forced, at least in a phenomenological setting, to admit nature has stochastic aspects. The outcome of measurements is from a practical perspective stochastic. The outcome has no underlying determinism that serves in utility in predicting them. Either with a ψ-epistemic interpretation there is a classical domain and outcomes are purely random, or in a ψ-ontic interpretation such as MWI that while there is some deterministic process, such as MWI splitting off of worlds, we can't access this.

    The really strange aspects to quantum mechanics lies in its nonlocality. This is just a fancy way of saying the quantum wave is extended in space, so a measurement can give an outcome where ever the wave happens to have some extent in that region of space. This does however lead to strange outcomes we are forced to admit because of our classical mental disposition. Our brains are wired to look at a classical world, but we have figured out how to make quantum measurements. As a result bipartite entangled electrons will with a magnetic field “here” exhibit a spin resonance in an RF system place “there.” This is where quantum mechanics really hits us with oddball stuff. Now we have quantum cheshire cats, where observables of a particle can manifest themselves in separate regions.

    https://www.google.com/url?q=https%3A%2F%2Fphys.org%2Fnews%2F2015-06-quantum-cheshire-cat-effect-standard.html&sa=D&sntz=1&usg=AFQjCNGBhTNYHOevlpvKdiEHeWDvLVbdqQ

    This is where I think quantum mechanics smacks us hard with our biases on how the world should work.

    ReplyDelete
  7. A.C. wrote: I agree with you that attempts to 'mix' art with science(usually) do not end well.

    I've been thinking about that and so far I'm short of good examples.

    In the early 1960's I saw for the first time the Bohr model for atoms and was instantly captivated. For me, the notion that all matter consisted of these submicroscopic solar systems was fantastic beyond imagination. Indeed, it exceeded God. Perhaps you and Sabine don't consider that to be a mix of art and science. Regardless of whether the Bohr model is "bad art" and "bad science," it gave me my first glimpse of the power of scientific models (even though I was too young to know what models were).

    In TV shows and movies, whenever there are explosions in space they are accompanied by an awful lot of noise. Even though it's bad science, the artistic side of people want to hear explosions.

    I've never been impressed with artistic depictions of four or five dimensions, but I don't fault artists and scientists for trying. I recall one episode of The Twilight Zone, "Little Girl Lost," in which a girl gets stuck in the fourth dimension. The father goes in after her and it's depicted as a three-dimensional lopsided obstacle course. Well, at least they managed to make it look a little scary, which was the point, after all.

    There's the amusing 19th-century novel "Flatland," which takes place in a two-dimensional world.

    It's Friday, so I'll offer a classic joke that's relevant to mixing art with science:

    A physicist, an engineer and a psychologist are called in as consultants to a dairy farm whose production has been below par. Each is given time to inspect the details of the operation before making a report.

    The first to be called is the engineer, who states: "The size of the stalls for the cattle should be decreased. Efficiency could be improved if the cows were more closely packed, with a net allotment of 275 cubic feet per cow. Also, the diameter of the milking tubes should be increased by 4 percent to allow for a greater average flow rate during the milking periods."

    The next to report is the psychologist, who proposes: "The inside of the barn should be painted green. This is a more mellow color than brown and should help induce greater milk flow. Also, more trees should be planted in the fields to add diversity to the scenery for the cattle during grazing, to reduce boredom."

    Finally, the physicist is called upon. He asks for a blackboard and then draws a circle. He begins: "Assume the cow is a sphere....”

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  8. @Lawrence Crowell

    Just imagine how strange and confusing the world will appear for those who behold that part of the world where quantum mechanics and relativity intimately collaborate. Such a vision will be feared and rejected as nonsense being so foreign from everyday experience.

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    1. Quantum gravitation is likely to be a domain that is radically different. Hawking radiation and the delay time from a black hole means the appearance of quantum states can be outside the horizon and on the stretched horizon in a nonlocal manner at the same time. This is without considering the interior state. So quantum gravitation is likely to have nonlocal features which are very strange. I will say though that I think this is a topological order with nonlocal entanglements that define the phase. This has a relationship through quantum critical point with with symmetry protected topological ordered states SPT, or super-SPT states that are on a physical vacuum. I think quantum gravitation is a sort of false vacuum physics. In this way physics measured by any realistic observer have field locality.

      Things in general are stranger than what we intuitively think. Astronauts have to go through expensive training to learn how to work in weightlessness. In effect just Newton's laws are a bit counter intuitive, and if you have ever taught freshman physics you know how difficult that job is. We are really Aristotelian in our sense of the world. Relativity makes things stranger, quantum mechanics really bizarre and quantum gravity will be even stranger.

      People in other areas have trouble understanding the natural world. In the United States I'd say about a third of people have a hard time imagining a past world without humans, and the same have trouble imagining a future Earth without people. About 10%, maybe more, of Americans think the sun and moon move around the Earth. There are problems with getting people to accept the theory that all biological organisms on Earth have a relatedness, a genetic relatedness at that, and they have diverged based on selection of various single nucleotide polymorphisms and other mutations of genes.

      In the United States there is a large ignorance industry that is not as prevalent in Europe or Japan, based on my experience with both. Much of this is tied up with religious ideology that has become highly political in recent decades. I fear the United States will say adieu to the whole western enlightenment program, even though this country was founded on that, and may drag the rest of the world with it.

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  9. Hi there, I would like to throw in a comment by Friedrich Schiller at this point. Looks like, the scientists have really given up on trying to say anything about nature as a whole - it´s as if Schiller had anticipated something like this to happen when he said (ready for this?)
    "The poets are in every aspect and by definition the true keepers of nature". („Die Dichter sind überall, schon ihrem Begriffe nach, die Bewahrer der Natur.“)
    Ten or twenty years after Schiller´s death scientists have laughed about this remark, but now while they figure out things WITHIN nature with their two mutually exclusive theories but can´t find a way out, they ain´t laughin any more, are they?

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  10. I guess physicists being guided by the beauty principle with their formulas is not really mixing art with science but rather physicists turning into poets inadvertently.
    Its yet another example of a "movement" defining their counterpart (physicists drawing a line between themselves and the "mere artists" in the late 19th century) and then turning into that counterpart in the course of time. History is full of examples for this.
    But take Schiller and Goethe, who co-operated before this (artificial?) divide: They both produced proper art, and Goethe´s "genetics" principle is now recognized as proper science as well (while it was denounced as "mere natural philosophy" in the late 19th century)
    Schiller would have applauded the beautiful formulas and cited his own poem "The artists":
    Nur durch das Morgentor des Schönen
    dringst du in der Erkenntnis Land
    an höhern Glanz sich zu gewöhnen
    übt sich am Reize der Verstand
    (Only through beauty´s morning-gate will you enter into the realm of knowledge etc.)

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  11. Thank you for this nice (and nicely commented) video. - It points at a topic which I find very general and important, that is randomness.
    At first it is very obvious and understandable that a technical random number generation yields only pseudo random results as an algorithm is per se deterministic.
    But then you say: quantum mechanics makes it possible to have true random sequences. Sure? How can we know? Is there any proof or at least a good argument? The situation is that the physical community believes this because Werner Heisenberg and Niels Bohr have postulated that physics is this way. And now it is treated as a fact. We know that Einstein’s opinion was clearly different here. But Einstein could not cope with Heisenberg / Bohr. The latter ones did have a better stand in the public. But is this a sufficient argument for all times?
    I find this situation embarrassing. I do not mean here the fact that today we do not have a better understanding. But I mean the fact that the physical (quantum) community does not see any reason to spend further thoughts on this. I find this important in general because there are so many physical statements in QM which have once been postulated in history but never been understood from a more basic logical level, and which were never questioned or discussed again. So, I suspect that here an important path is cut off without necessity by which a further development could be initiated.

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    Replies
    1. antooneo,

      I am talking about quantum mechanics, for which what I say is of course correct. You are asking instead if not there may be a different underlying theory which is deterministic. You are wrong in stating that no one spends further thoughts on this. It is as a matter of fact something I am working on with a postdoc.

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    2. This quote here from a letter to Max Born seems to suggest that determinism was not the main issue for Einstein with respect to QM.
      It was mainly the lack of realism in the Copenhagen interpretation as e.g. Tim Maudlin suggest (well … non-local realism).
      (Lee Smolin is more ambivalent: on the one hand he wants to have a real flow of time, but on the other hand I guess sees no way how randomness could ever enter …)

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    3. Sabine,

      you mean that quantum mechanics is inevitably connected to true randomness. That is general main stream; but inevitably connected in this way?
      Let's assume for a moment that the processes in QM are not truly random but follow an algorithm which we do not understand. Would this make any difference in what we see in experiments? So, why not think about parts in QM which could be treated differently?

      My concern is that we still follow Heisenberg is his advice not to think about details in particle physics and so not to go into the next lower level of reductionism.

      I have made a repeated experience with this. I have asked several colleagues working in particle physics regarding the Pauli principle: Do we in the mean time know a cause of this principle? The persons I have asked this question reacted somewhat irritated saying: No, we do not, and there is no reason to look for it. There are facts in nature which are as they are and it makes no sense to ask further questions.

      If this is general position, what could be the reason to invest any activity into physics?

      Reimond,

      regarding Einstein: He said this famous sentence: "God does not play dice." I think that is it.

      Delete
  12. Off topic: Did you ever talk about Glashow's review of your book on the Inference website?

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  13. aydemir,

    No. They invited me to write a reply. I did not.

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  14. I've just recently been looking through Chris Ishams book on the structure of Quantum Mechanics where he writes, whereas philosophically speaking, relativity and general relativity provoked new questions about space and time, whereas QM provoked questions about ontology. That is what is it we mean by a thing, and also, implicitly, what we mean by change. In these terms, he writes about the Copenhagen interpretation as anti-realist, since it refuses to give actual things actual properties, but only after they have been 'measured' - whatever the latter means. There have been, he writes other interpretions that try to ascribe reality to quantum objects. For example, Margeneau says properties are 'latent' until they become actualised through measurements. Popper has a similar kind of ontology, which he calls 'propensity'. Moreover, and more interestingly, Heisenberg 'in later work drew analogies with the old Aristotelian notion of *potentiality*...the probability of an event has to be considered as some sort of numerical measure of the latency/propensity/potentiality of a particular event will occur'.

    I think these ideas are interesting as they take the whole of quantum theory including the measurement/wave reduction postulate seriously yet attempting to return us to an ontology that is realist, compared to many worlds, which only takes the deterministic evolution seriously, and the Copenhagen interpretation which, though also called the pragmatic interpretation, is simply sitting on the fence and refusing to commit to anything.

    I also find it interesting that Heisenberg thought of the old philosophical idea of potentiality as apposite for QM. Its important to recognise, in connection with this, that this was Aristotles solution to the problem of change/reality as opposed to the theory which also claimed to solve this problem, that of atoms, and which he dismissed.

    If Heisenberg is correct that potentiality has the potential (pun intended) to help solve the ontological problems of QM then it would be supremely ironic to think that QM, thought of as an archetypal modern theory, has raised profound philosophical questions on ontology already thought through two and a half millenia ago! It might also perhaps stop people thinking QM is strange (presumably in contrast to Newtonian type 'classical' physics - which given what Heisenberg points out - isn't perhaps so classical) and to think that its Newtonian type physics that is strange/weird!

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  15. Bee what do you think...

    https://phys.org/news/2019-06-quantum-simulation-unruh.html

    A quantum simulation of Unruh radiation

    In this article, a Bose condensate is pumped with a magnetic field and that field extracts energy from the vacuum.

    Could the gigahertz pumping signal that is being uses in the LENR reactor milk the vacuum using a super fast oscillating magnetic field to produce energy from the billions of polaritons in a polariton condensate on every cycle of the pumping signal?

    ReplyDelete

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