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Study Says Quantum Wavefunction Is a Real Physical Object 373

Posted by Soulskill
from the don't-trip-on-the-wavefunctions dept.
cekerr writes with this excerpt from an article in Nature "The wavefunction is a real physical object after all, say researchers. ... the new paper, by a trio of physicists led by Matthew Pusey at Imperial College London, presents a theorem showing that if a quantum wavefunction were purely a statistical tool, then even quantum states that are unconnected across space and time would be able to communicate with each other. As that seems very unlikely to be true, the researchers conclude that the wavefunction must be physically real after all. David Wallace, a philosopher of physics at the University of Oxford, UK, says that the theorem is the most important result in the foundations of quantum mechanics that he has seen in his 15-year professional career. 'This strips away obscurity and shows you can't have an interpretation of a quantum state as probabilistic,' he says."
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Study Says Quantum Wavefunction Is a Real Physical Object

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  • by Anonymous Coward on Friday November 18, 2011 @02:06PM (#38100840)

    One of the stumbling blocks for learning this stuff at school was the people were hung up on the idea of "this-space", "that-space". It was a revelation to me that when they said "probability space" it was only a space in the mathematical sense (ie, something with N dimensions that could be graphed if N were not too large).

    The way I saw it, people were prejudiced to believe that these were real spaces, the prejudice being that physics is strange at that level, thus there must be strange bizarre types of space. Nope. They were just things with N numerical characteristics.

    Now you're telling me there really are strange spaces? That sucks.

    • Data vs Logic (Score:5, Interesting)

      by VernonNemitz (581327) on Friday November 18, 2011 @03:28PM (#38101886) Journal
      The funniest thing is that this paper is coming out in the midst of the discussion of faster-than-light neutrinos. According to the interpretation presented in the article blurb at top, FTL neutrinos should be forbidden. If they actually exist, however, then that means that the quantum wave function really is a stastical thing and not a physical thing.
      • Re:Data vs Logic (Score:5, Interesting)

        by jd (1658) <imipak@noSPam.yahoo.com> on Friday November 18, 2011 @04:08PM (#38102382) Homepage Journal

        The latest experiments match the original observations. In the past day or so, they tweaked a number of parameters - such as the length of pulse - to see if more precise timing and more precise correlation would have any impact. The numbers didn't change. So, Scotty was wrong - we CAN break the laws of physics! (But the fine is 2795 Ningis if we're caught.)

      • by Anonymous Coward on Friday November 18, 2011 @04:14PM (#38102448)

        Since it is a quantum wave function, couldn't it be both physical and statistical at the same time?

  • Sensible (Score:4, Interesting)

    by exa (27197) on Friday November 18, 2011 @02:07PM (#38100854) Homepage Journal

    "Abstract objects" or "mathematical objects" don't exist in general, so this suggestion is rather plausible. Of course, the reality of the wave function had been proposed before, but new arguments are sorely needed in philosophy of quantum mechanics.

    • Re: (Score:3, Interesting)

      by ackthpt (218170)

      "Abstract objects" or "mathematical objects" don't exist in general, so this suggestion is rather plausible. Of course, the reality of the wave function had been proposed before, but new arguments are sorely needed in philosophy of quantum mechanics.

      The most shocking realization is this: Quantum Mechanics are ceasing to be Crazy, they're Real and Definite.

      It's like a part of my childhood just died.

      • Re:Sensible (Score:4, Interesting)

        by exa (27197) on Friday November 18, 2011 @03:10PM (#38101668) Homepage Journal

        There have been several scientifically plausible interpretations. One thinks of MWI for instance.

        It's just that some rather big names have unwittingly advocated superstitious, and completely nonsensical interpretations, the most famous of which are Copenhagen interpretation, Von Neumann Interpretation, and Penrose's assorted BS.

        • by rjh (40933) <rjh@sixdemonbag.org> on Friday November 18, 2011 @04:09PM (#38102390)

          The fact you called MWI "scientifically plausible" should be the first sign you don't have the first clue what you're going on about.

          For MWI to be "scientifically plausible" it would have to make predictions which could be confirmed or falsified via experiment. That is, in essence, what science is: the subjecting of ideas to experimental test. (Go ask Zombie Feynman [xkcd.com] if you don't believe me.)

          I've yet to hear any testable predictions MWI makes that would allow us to differentiate it from, say, Copenhagen. Maybe that's changed since I last dove into things (and if it has changed, I hope you'll tell me so), but I kind of doubt it.

          David Deutsch is famous for saying that MWI is the only interpretation that gives any kind of sense to quantum computation. And, you know, I'm inclined to agree with him. That doesn't mean MWI is correct, though: it just means that the other interpretations do not satisfactorily explain those phenomena, not that MWI is the only possible interpretation that could give sense to quantum computation.

          Also, given Copenhagen was first developed by Werner Heisenberg, it's kind of crazy to claim that Copenhagen is a "superstitious and completely nonsensical" interpretation. If I have to choose between exa on Slashdot being right when he says Copenhagen is superstitious and completely nonsensical, and Zombie Werner Heisenberg being right when he says that exa on Slashdot is misunderstanding Copenhagen, well... I'm going to side with Zombie Werner Heisenberg, you know?

          • by blueg3 (192743)

            David Deutsch is famous for saying that MWI is the only interpretation that gives any kind of sense to quantum computation. And, you know, I'm inclined to agree with him.

            His understanding of quantum computation is also astoundingly flawed.

      • Except ... (Score:5, Insightful)

        by tomhudson (43916) <barbara.hudsonNO@SPAMbarbara-hudson.com> on Friday November 18, 2011 @03:23PM (#38101830) Journal

        As that seems very unlikely to be true, the researchers conclude that the wavefunction must be physically real

        I could go back a couple of centuries and make the same flawed logical argument - "as it is unlikely that the earth moves, therefore it MUST be the center of the universe."

    • by Hatta (162192)

      Of course they exist. They have properties. Something non-existant can't be said to have any properties besides non-existance.

    • by melikamp (631205)
      In what sense do mathematical objects not exist? The physical sense? I am agnostic about that. Philosophically speaking, the world could turn out to be a giant continuous massively parallel computation, and then physics IS math, and nothing BUT mathematical objects exists. I can't think of any way to test for that. Although I have to admit, a non-math universe may seem more credible simply because we can't even begin to draw a mathematical theory of everything. All of the current theories seem to break down
    • > "Abstract objects" or "mathematical objects" don't exist in general,
      Uh, if they don't exist, then how are you able to _refer_ to them then?

      Ask any mathematician if infinity exists, and they will go "Of course, stupid". You are confusing existence with being dependent on the physical, when they are in fact meta-physical. i.e. Physical Existence is sufficient, but not a requirement.

      Proof:
      If time is physical, then show it to me.
      If numbers are physical, then show it to me.

      The fact that we can _separate_ m

  • by bugs2squash (1132591) on Friday November 18, 2011 @02:11PM (#38100888)
    That there is uncertainty in the amplitude of the wave function too ?
  • by roguegramma (982660) on Friday November 18, 2011 @02:13PM (#38100910) Journal

    This is what they have proven:
    If a quantum wavefunction is purely a statistical tool, then quantum states that are unconnected across space and time are able to communicate with each other.

    The rest is speculation.

    IMO one observer's wavefunction is the other observer's statistical tool, where an observer is any ensemble of particles.

    By the way, the wikipedia article on Bell's inquality stated something similar years ago.

    • by blueg3 (192743) on Friday November 18, 2011 @02:18PM (#38100976)

      If a quantum wavefunction is purely a statistical tool, then quantum states that are unconnected across space and time are able to communicate with each other.

      Actually, what they've proven is that either the wavefunction is a real object and not a statistical tool or quantum states that are unconnected across space and time are able to communicate with each other.

      This is fairly similar to, though not the same as, Bell's Theorem.

      The rest is speculation.

      The paper is actually quite clear on their claims. The speculation was added by others, but is a reasonable interpretation.

      What's definitely speculation is your comment, which seems to have no real basis in quantum mechanics:

      IMO one observer's wavefunction is the other observer's statistical tool

      • by Anonymous Coward on Friday November 18, 2011 @03:00PM (#38101522)

        The big difference from Bell's theorem is that in Bell's theorem, the quantum states are entangled. Here they are not, and the idea that un-entangled states would be able to communicate with one another is a bit more problematic than the idea that entangled states would be able to communicate with one another.

        • by Dr. Spork (142693) on Friday November 18, 2011 @03:07PM (#38101606)
          Exactly. And that difference is very important. It's quite an understatement to say that information-passing between unentangled states is "a bit more problematic" than EPR-style instant communication.
        • by epine (68316)

          The big difference from Bell's theorem is that in Bell's theorem, the quantum states are known to be entangled.

          In every experiment I've read about, the entanglement is known by how the particles are created. But here's the question I never see answered: is it possible, given two particles you know nothing about, to prove the particles are not entangled?

          If you can't prove any given pair of particles are not entangled, then perhaps entanglement is the natural state, and particles known to not be entangled (

    • by jd (1658) <imipak@noSPam.yahoo.com> on Friday November 18, 2011 @04:15PM (#38102462) Homepage Journal

      If quantum states that are unconnected across space and time are able to communicate with each other, then:

      a) Single photons can interfere with themselves (has been done)
      b) Interference patterns will work across time just as well as they can across space (has been done)

      So unless I'm missing something, their claim that it is unlikely would appear flawed.

  • Weird (Score:5, Funny)

    by 0123456 (636235) on Friday November 18, 2011 @02:16PM (#38100952)

    I don't remember covering 'proof by claiming that something is unlikely' in my Physics degree.

    • Re:Weird (Score:5, Funny)

      by blueg3 (192743) on Friday November 18, 2011 @02:19PM (#38101002)

      Did they cover reading the paper instead of a media summary? Because it's a pretty important skill in science.

      • Re:Weird (Score:5, Informative)

        by BitZtream (692029) on Friday November 18, 2011 @02:31PM (#38101126)

        This isn't science, this is slashdot. Facts are out the door here.

      • Re: (Score:2, Insightful)

        by tgd (2822)

        I blame the trend in the 90's of feeling it was unfair to the stupid children to point out they're stupid.

        Now an entire generation thinks their beliefs are facts because their dimwit parents and teachers never pointed out to them that they were idiots.

        • by geekoid (135745)

          "Now an entire generation thinks their beliefs are facts "

          what do you mean now? it's always been that way, the 90s don't even enter in to it. The only difference now is they have ways to communicate their belief over a vast area.

          And you should tell children they are stupid, but you should tailor education to what is challenging to the child.

          Once you tell people are stupid, they start to internalize it and then thing they can't do anything.
          Should they be told they are correct when they aren't? no. Should the

    • Re:Weird (Score:4, Insightful)

      by MozeeToby (1163751) on Friday November 18, 2011 @02:32PM (#38101142)

      Sure you did, it's called Occam's Razor. Which is more likely: All the planets in the solar system travel around the sun in approximately elliptical orbits OR All the planets in the solar system orbit the Earth in a complex arrangement of circles within circles within circles? Now that being said, I'm not sure that you can arbitrarily say disconnected quantum states are likely than connected ones, but allowing them to communicate would seem to posit some communications medium that we have never seen evidence of, so if I had to choose I'd say they are unable to communicate.

      And besides all that, as many people have already pointed out, the claims of 'proof' have been added by the media; the actual research just says it's one or the other making no judgement as to which.

      • Bad example (Score:5, Insightful)

        by rjh (40933) <rjh@sixdemonbag.org> on Friday November 18, 2011 @02:59PM (#38101498)

        Copernican theory was picked up fairly quickly because it offered a simpler view of the cosmos. Astronomers bought into it largely because of its simplicity -- in effect, following Occam's Razor. It took until the early twentieth century for Einstein to say "you're all a bunch of doofuses: Ptolemaic theory is just as valid as Copernican, it all depends on your frame of reference." Thanks to relativity we now know beyond any shadow of a doubt that Ptolemaic epicycles are equally valid: they're just more complex. There is no privileged frame of reference. It is as true to say the Earth circles the Sun as it is to say the Sun circles the Earth -- it's just that the equations are neater in one frame of reference, not that they are correct. This bears repeating: according to special relativity, there are no privileged frames of reference.

        Naively applying Occam's Razor to the question leads people to a false sense of certainty: they tend to think, "I've applied Occam's Razor, therefore I am likely choosing the better answer," without ever thinking, "did I formulate the question correctly in the first place?"

        Don't get me wrong, I like Occam's Razor. But when people use Copernican-versus-Ptolemaic theories as an example of Occam's success, well... that tells me a quick lesson needs to be given on how Occam's Razor utterly fails in that case.

        • by Luyseyal (3154)

          General principle of relativity [wikipedia.org]

          Special relativity predicts that an observer in an inertial reference frame doesn't see objects they'd describe as moving faster than the speed of light. However, in the non-inertial reference frame of Earth, treating a spot on the Earth as a fixed point, the stars are observed to move in the sky, circling once about the Earth per day. Since the stars are light years away, this observation means that, in the non-inertial reference frame of the Earth, anybody who looks at the stars is seeing objects which appear, to them, to be moving faster than the speed of light.

          Since non-inertial reference frames do not abide by the special principle of relativity, such situations are not self-contradictory.

          My take is that it's better to pick the "most inertial" frame you have available. It is a heuristic like Occam's Razor but the upshot is the math is easier.

          -l

          • by rjh (40933)

            Oh, sure. My own personal rule is "prefer the reference frame that makes the math easiest." However, my complaint was using Occam's Razor to decide which was more likely to be true: Ptolemy's or Copernicus's view of the heavens. This is a misuse of Occam: it overlooks the fairly deep truth that they are both equally true from within their given frames of reference.

            Please, don't misunderstand me: I love making the math easier. :)

            • by Millennium (2451)

              This. Occam's Razor is an experimental guide, not a standard of scientific proof. It's one of a number of maxims that gets abused by armchair scientists who think it says something it doesn't.

              Likewise, this paper doesn't actually prove anything. It does appear to disprove one popular interpretation of quantum physics, by showing that it contradicts observed data. But by itself, that does not prove the other popular interpretation to be necessarily true.

        • by Dr. Spork (142693)

          What? It's not even close to true that Einstein showed Ptolemeic theory to be equivalent to Copernican theory. Ptolemeic theory postulated the existence of spheres of revolution, and epicycles on those spheres, and more refined versions had epicycles on the epicycles.

          It's ok for you to be confused about physics. Many good people are. It's not ok for something this scientifically absurd to get modded +5 Insightful on a blog of nerds.

          • by rjh (40933)

            The AC has already answered this for me, so I'll just say it: yes, that.

            Ptolemy's original vision was accurate for the measurements of the day. As observations got better, the model was patched -- as you say, with epicycles within epicycles. If we were to continue to patch the Ptolemaic version (which shouldn't be surprising, given how many patches we've made to the Copernican version), we would have an Earth-centric model of the universe with the heavens moving in strange, complex patterns around us. Th

        • by mbkennel (97636)

          That's also a bad example, nothing with Einstein was necessary. You can derive the equations of motion in the different frames perfectly well with Newton's mechanics (Einsteinian corrections are tiny), and yes the description really is simpler in some frames than others.

          It was really Kepler's refinements which astronomers bought into, because of its experimental predictability; and then Newton explained Kepler's results from first principles, unifying gravitation on the ground and in the sky, which was the

        • I'm sorry, but I had to correct this:

          according to special relativity, there are no privileged frames of reference.

          This is quite untrue. By a 'privileged frame of reference', physicists have always meant ones in which the laws are particularly simple. There are, in special relativity, a privileged set of frames called internal reference frames. These are the same priviliged reference frames as existed under Newton's Laws. What Einstein did is hypothesize (to explain the negative result of the Michelson-Mo

      • Sure you did, it's called Occam's Razor.

        Occam's Razor doesn't say anything about correctness.

        Which is more likely: All the planets in the solar system travel around the sun in approximately elliptical orbits OR All the planets in the solar system orbit the Earth in a complex arrangement of circles within circles within circles?

        If they give the exact same predictions, both matching observations with the same accuracy and precision, then you take the easier to calculate one. And that is what Occam's Razor says, actually: that it makes no sense to use anything more complex than you have to. As for which one is "correct", if both give the same position to at all points to all the planets, that means they are equivalent.

        And besides all that, as many people have already pointed out, the claims of 'proof' have been added by the media; the actual research just says it's one or the other making no judgement as to which.

        Yep.

    • Re:Weird (Score:4, Insightful)

      by Anonymous Coward on Friday November 18, 2011 @03:11PM (#38101676)

      Then your physics degree is worthless.

      One of the most basic principles of science, in fact I would say it's the single most important principle in science, is that nothing is ever completely proven. It's only probabilistically proven, meaning the chance of it being wrong is so small that you can basically rule out that possibility.

      What is the concept of falsifiability, one of the key principles in the scientific method? You try everything you can to disprove your hypothesis. You get everyone else to try and disprove it. You hit it with everything you've got, and if it withstands the assault, then you can say it's proven. But it's only proven to be true under the conditions that you used to test it. In other words, no matter how hard you try, it still might not be true. It's only extremely unlikely not to be true.

      Ironically, that's the greatest strength of science - that it's fallible. And it openly admits that fact. It rejoices when somebody tells it that it was wrong all along, because that means there's still more to discover. That's the driving force behind science. We test what we can, claim something is proven after the tests support it, but always leave open the possibility that we'll discover some new information that helps to refine or sometimes even replace the theory. The only "proof" of anything is the claim that it's a more likely explanation of your observations than any other possibility.

      Granted, the claim that something is unlikely is not itself sufficient to disprove it, and perhaps that's what you meant, so maybe I'm being a little harsh. My point is simply that every "proof" is still just a claim. It just happens to be the claim most supported by the evidence.

  • Wasn't this hinted at by those oil-droplet-on-vibrating-medium experiments that partially reproduced the wave/particle duality?
  • dare step on my wavefunction, mister! Or I'll have to send my engevectors at you!
  • Prince de Broglie... (Score:3, Interesting)

    by theNAM666 (179776) on Friday November 18, 2011 @02:23PM (#38101048)

    Yawn. Did these guys ever read Prince de Broglie?

    http://galileo.phys.virginia.edu/classes/252/Bohr_to_Waves/Bohr_to_Waves.html [virginia.edu]

    http://en.wikipedia.org/wiki/Louis_de_Broglie [wikipedia.org]

    A particle is a wave is a particle-wave; all we can say about the universe, is what we can say about the universe; there's no such thing as a "real physical object."

  • by mbone (558574) on Friday November 18, 2011 @02:25PM (#38101066)

    I would bounce this paper as a reviewer. It appears to be a recasting of Bell's Theorem, but it doesn't reference ANY of that work.

  • by bigsexyjoe (581721) on Friday November 18, 2011 @02:27PM (#38101084)
    What's the difference? What is the difference between something being a "mathematical description of reality" and being real? I mean you can go back and forth between if numbers are real, etc. Have they discovered something "more real" than they previously thought?
    • What's the difference? What is the difference between something being a "mathematical description of reality" and being real? I mean you can go back and forth between if numbers are real, etc. Have they discovered something "more real" than they previously thought?

      Math is the study of patterns.
      Physics is the study of reality.

      We use math to describe physics. Our current quantum math tells us what will happen. Our best quantum math is currently probabilistic. All our finest measurements can only give us a guess as to what will happen. The math describes what we see.
      If the wave function is a result of a real, physical thing, we can potential learn more about the real, physical thing, and perhaps measure that, and get take that into account in our math, thus removing

    • Re:Dumb question (Score:5, Informative)

      by BitZtream (692029) on Friday November 18, 2011 @02:44PM (#38101300)

      Its more like this mathematical construct we had to describe something we really didn't understand ... but let other mathematical constructs work out properly and achieve results that matched reality ... in fact appears to be the proper mathematical construct to define a portion of reality.

      But thats what the summary says, not what the article says.

      What the article says is more long the lines of:

      Well, either this math is right or faster than light communications are possible. As far as we can tell, we see evidence that suggests faster than light communication is possible, so we conclude that we were probably right about this mathematical construct.

      Considering that we have conflicting (and also unproven) reports of faster than light travel, we have two directly conflicting scientific theories on the table at the moment that can not possibly be right.

      Or it could just mean that neutrinos are faster than light and the universal speed limit is actually neutrinos speed, not photon speed.

      Truth be told, it all doesn't matter until we achieve the speed of bad news.

    • by kwikrick (755625)

      It's a very good question.

      I'm not a physicist, and I couldn't understand most of the paper, but what it seems to suggest is that a quantum state must be somehow represented or stored in a physical object. So the quantum state is not simply a statistical description of how particles interact, but is something 'real' that interacts with particles.

      I would guess this physical object would take the form of a particle and also take the form of a wave, i.e. a wave-particle or whatever you call it, like many other

  • So does this support or refute the contention that reality is made up of a very very large number of universes constantly being created at each quantum step? Isn't that what the Copenhagen interpretation implied?

    • by mbone (558574)

      Probably neither, and that is a competing interpretation to the Copenhagen one.

    • So does this support or refute the contention that reality is made up of a very very large number of universes constantly being created at each quantum step?

      If the title of the Slashdot story were factually right, one could say that it in some sense support it. But no more than it also supports the notion that there are physical particles guided by the wave function in a single, non-branching universe. Because both interpretations assume that the wave function is physically real (as do some other do, like t

  • Gotta love quantum news posts: meaningless and meaningful at the same time, like a newspaper written by Schroedinger's Cat.

  • Lumo weighs in... (Score:4, Informative)

    by Freddybear (1805256) on Friday November 18, 2011 @03:06PM (#38101598)

    http://motls.blogspot.com/2011/11/nature-hypes-anti-qm-crackpot-paper-by.html [blogspot.com]

    "Whatever way you choose to read the text [of the paper by Pusey et al], it makes no sense whatsoever. How they suddenly jump to the conclusion that there is a problem with the probabilistic meaning of the wave function remains completely mysterious."

    • Motl may be brilliant mathematically but he is a prejudiced paranoid whose dubious behaviour into trying con arXiv into censoring scientists he disagreed resulted in his "resignation" (aka firing) from his post at Harvard.
  • Wave function is a real object? You gotta be kidding. Next thing you will say "corporations are people". Oh! wait..
  • So, what I'm not getting is this: If a waveform is a real physical object and not just a conceptual statistical function, what is the physical nature of this object? Is it a half-dead Schodinger's Cat? Or is it a world where the Cat lived superimposed on a world where it died? Is it (gulp) both?
  • the new debate (Score:5, Interesting)

    by Goldsmith (561202) on Friday November 18, 2011 @03:41PM (#38102042)

    In the Nature blurb, there's a bit of discussion at the end that quantum states might all be linked, entangled or not.

    In most physics classes, you learn quantum mechanics by calculating the interactions between isolated states. This thought process is natural and useful for certain areas of physics, but you end up worrying about hidden variables and how particles which are essentially in different universes can possibly communicate. This view does not need the wave function to be real, it can just be a statistical tool.

    An alternative way of thinking about things is the idea that there are no isolated states (and no measurement apparatus which can exist outside the quantum system). From that point of view, one wave function is sufficient to describe the entire universe, traced back to the big bang. You don't need to worry about spooky action, everything obeys causality just fine assuming the wave function is real. There are some cosmological issues still, and it's not clear such a unified state is possible in an infinite universe.

    At least we're starting to all agree wave functions are real and not just a statistical tool.

  • ... its a probability function. Its both!

    Stand by to see which theory Schrodinger's cat buries in his litter box.

  • by hweimer (709734) on Friday November 18, 2011 @04:06PM (#38102366) Homepage

    I saw the paper when it originally appeared on the arXiv. They claim to randomly prepare a pure state. This is a contradiction in itself, as von Neumann and others have already shown decades ago that random ensembles of states (or local parts of a globally pure state) have to be described by mixed states. If one uses the proper mathematical concepts, their results vanish immediately.

  • All they proved is that the simple statistical model is inadequate to describe why spooky-action-at-a-distance is not more commonplace.

  • I'm sorry have I missed something, what does the term exists mean in this context?
    Don't all ideas and mathematical constructs , including dreams exist? If they didn't we would not have words to describe them, because no one would ever have experienced them.
    Is there some definition for the word exists that doesn't require recourse to metaphysics for it's definition?
    I mean you might say occupies objectively measurable space time , but isn't that a pre-requisite for experimentally derived data?

  • by rs1n (1867908) on Friday November 18, 2011 @04:51PM (#38102942)

    What a crappy summary and crappy article. The wavefunction is no more a real object than any other mathematical function. The statement: "f(x)=x^2 is a real object" has no valid meaning whatsoever. To even call it a theorem is ridiculous. Likewise goes for the wavefunction. It is a tool to model our "real" world. Some models are exact and precisely describe the "real" world. Other models only work under certain assumptions and/or reference frames.

    If you actually read the research paper, the authors consider the question of whether a quantum state is a physical property attached to a system. Said another way, do quantum systems actually exist? Or are they purely theoretical? From the article:

    "The statistical view of the quantum state is that it merely encodes an experimenter's information about the properties of a system. We will describe a particular measurement and show that the quantum predictions for this measurement are incompatible with this view."

    The gist of it is that they have produced a result (didn't read the whole thing to actually figure out what their result was) which relied mainly on three assumptions:

    • 1. "if a quantum system is prepared in isolation from the rest of the universe, such that quantum theory assigns a pure state, then after preparation the system has a well dened set of physical properties"
    • 2. "it is possible to prepare multiple systems such that their physical properties are uncorrelated"
    • 3. "measuring devices respond solely to the physical properties of the systems they measure"

    Since their result is incompatible with the statistical view of quantum states, it must due to one of the assumptions above. They don't actually make the claim that quantum states are physical properties (like length, width, height, mass, etc. are). In fact, they conclude with:

    "More radical approaches are careful to avoid associating quantum systems with any physical properties at all. The alternative is to seek physically well motivated reasons why the other two assumptions might fail."

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