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Science

Making Sure Our Lab Equipment Isn't Tricking Us 108

Posted by Soulskill
from the ghost-in-the-machine dept.
An anonymous reader writes "In a newly published paper, MIT researchers propose an experiment that may close the last major loophole of Bell's inequality. The test is to see whether, as far-fetched as it sounds, a particle detector's settings conspire with events in the shared past to determine which properties of a particle to measure — a scenario that implies that a physicist running the experiment does not have complete free will in choosing each detector's setting. MIT’s David Kaiser says, 'It sounds creepy, but people realized that's a logical possibility that hasn't been closed yet. Before we make the leap to say the equations of quantum theory tell us the world is inescapably crazy and bizarre, have we closed every conceivable logical loophole, even if they may not seem plausible in the world we know today?' The test involves quasars, telescopes, and lots of deep, deep space. It was published this week in the journal Physical Review Letters (pre-print available at the arXiv)."
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Making Sure Our Lab Equipment Isn't Tricking Us

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  • Please! (Score:5, Funny)

    by NotQuiteReal (608241) on Friday February 21, 2014 @11:25AM (#46303957) Journal
    Don't anthropomorphize the machines. They hate that, and will go back into their past to get you!
    • If only I had mod points today... I had some last week, so I'll be right back.

      Sincerely,
      A confocal microscope
  • Why can't they use a PRNG to dictate the detector settings? Pick a high quality PRNG, seed it with the first prime number. Run the experiment N times. Restart, seeding it with the second prime number, and run the experiment for N times again. Repeat M times until satisfied.

    Then re-run the above with a different type of high quality PRNG.

    Am I missing some big clue?

    • by Anonymous Coward
      Who comes up with the formula for the PRNG? "They" could've conspired to choose a convenient PRNG a few decades ago. So you move from ms to decades. The authors's approach moves by 20 orders of magnitude in the past.
    • by swschrad (312009) on Friday February 21, 2014 @12:52PM (#46304545) Homepage Journal

      a much simpler explaination... the detector material is still groaning from the last collision and doesn't have its calibrated act together for the next one. you detect subatomic particles, after all, by watching what happens when they distort a known material, and extrapolate from the distortion what whacked into it. whacking things causes them to go off kilter. from black bands and reduced light in fluorescent light tubes to bright-bloom in old TV cameras to getting wacky when you leave a dark room and are sun-blinded, this has been a known phenonema as long as we have been around.

    • by Immerman (2627577) on Friday February 21, 2014 @02:43PM (#46305201)

      AC has it right - *any* source of (psuedo)random numbers from causally connected sources is suspect, and no number of repetitions will rule out forces that retroactively ensure consistency. Frank and Bob could be simultaneously flipping coins on the opposite side of the planet, yet still be causally connected by the fact that their results will determine the settings for an experiment that the universe decrees must be consistent with certain principles. Even this experiment won't be able to close the loophole completely - it could be that the experiment and its settings were already fully defined in the first few instants of the universe while the not-matter that would eventually become the quasars was still causally connected. Basically this is a negative-evidence only experiment - it can't show that hidden variables aren't controlling QM, but it could potentially show that they are. Unless of course the hidden variables ensure that the choice of quasars will be such that the experiments yield consistent results. Though if they do it multiple times with different quasar pairs the odds of that being possible drop dramatically.

      • What if they seed the PRNG with cosmic ray data? And/or XOR the PRNG with cosmic ray data?
        I think if that also shows Bell correlations, it would only leave two possibilities:
        * Either there's a god-like entity determining the results and actively misleading us. In which case, no amount of experimenting would help.
        * Or quantum mechanics is right.

        OK, there's third one:
        * Actually the correlations don't really exist, but due to an extremely unlikely sequence of events the data still looks like we have one (simil

        • Or a fifth one that General Relativity is incorrect and the universe follows an FTL model. In this case the present exists and so is fixed but the past does not literally exist (except as the integrated information state of the present) and so is basically flexible, as is the state of the future. Bells theorem does not apply to FTL theories anyway because they can go beyond local (STL) variables to absolute contexts - .

          I have been working on an FTL model for ten years and it actually puts quantum mechanics

  • This is an elaborate experiment that will prove - we don't know everything in physics, yet. Seems like there are better ways to spend your time and creativity.
    • I don't think you realize how expensive it usually is to do experimental physics that pushes the bounds of our understanding. This sounds like it'll be cheaper than particle accelerator experiments, and may yield unexpected results.

      Expected results are good too, then we can move on.

  • by clovis (4684) on Friday February 21, 2014 @11:50AM (#46304117)

    From the article:
    The idea, essentially, is that if two quasars on opposite sides of the sky are sufficiently distant from each other, they would have been out of causal contact since the Big Bang some 14 billion years ago, with no possible means of any third party communicating with both of them since the beginning of the universe — an ideal scenario for determining each particle detector’s settings.

    Why would you assume that if they're 14 billion years apart that it would be any different than 14 seconds apart in time, at least in regard to entanglement?
    " with no possible means of any third party communicating" makes me think "we don't know of a means to communicate"
    Could the outcome of the experiment could show either action at a distance, or some faster-than-light communication without excluding either possibility?
    If it does happen that entanglement went away, it would be most interesting.

    • by Goldsmith (561202) on Friday February 21, 2014 @11:59AM (#46304187)

      Exactly right.

      There are two possibilities:
      1) The universe is infinite, and it would be possible to find two quasars which never shared a quantum state.
      2) The universe is not infinite and it is not possible to find two of anything which have never shared a quantum state.

      They've completely failed to close this loophole.

      • by Anonymous Coward

        They're not looking for quasars with no shared quantum state, they're looking for quasars with no shared history. As in, outside of eachother's past light cone. The goal is to prove that there's no classical explanation for the observed excess in violation of Bell's inequality.

        • by Immerman (2627577)

          Yes, but the point is that, given a non-infinite big-bang origin, there's no such pair of quasars in existence - *all* the "stuff" that eventually became matter and quasars was causally connected for the first few instants of the universe. Assuming everything remains consistent with QM this just sets a really high lower limit on the strength of any free-will nullifying effects.

          Or not - how exactly are the quasars chosen? Nullification need only be strong enough to ensure the "right" independent sources a

        • They're not looking for quasars with no shared quantum state, they're looking for quasars with no shared history. As in, outside of eachother's past light cone. The goal is to prove that there's no classical explanation for the observed excess in violation of Bell's inequality.

          All light cones lead to the big bang, if you believe in that sort of thing.

      • Even if the universe is infinite, the observable part of it is finite, and there's evidence (the homogeneity of the cosmic microwave background) that all of it was once causally connected. A quasar that is outside the observable part of the universe won't help you because you can't use anything it emits — it doesn't reach you.

    • by MozeeToby (1163751) on Friday February 21, 2014 @12:09PM (#46304249)

      You cannot have entanglement without interaction, you cannot have interaction between two things that lie outside of each other's light cones.

      To be fair, you can't have interaction outside of your light cone without also having faster than light communication. But you can't have faster than light communication without also having the possibility of sending messages back in time. And you can't have the possibility of sending messages back in time without breaking causality. So, on the one side you have the assumption that causality doesn't exist and faster than light communication is possible (both of which are contradicted on scales from pico-meters to billions of lightyears), on the other side you have the assumption that information can't travel faster than light (which again, seems to be supported by every experiment and observation made in human history).

      • > And you can't have the possibility of sending messages back in time without breaking causality.

        Incorrect assumption.

        Your fallacy is assuming time is one-dimensional. There are two levels to time: Linear and Non-Linear. Or to put it a different but related way, you can know the past, present, and future, but not yet experienced it.

        > you have assumption the assumption that causality doesn't exist and faster than light communication light communication is possible (both of which are contradicted on s

      • by naasking (94116)

        You cannot have entanglement without interaction, you cannot have interaction between two things that lie outside of each other's light cones.

        This is only true if interaction is local, which is not true in QM's configuration space. This is why hidden variables can never be ruled out without also ruling out QM as a whole.

      • by Immerman (2627577)

        Actually not quite, there's three possibilities and you can pick any two without problems.
        (1) Relativity is completely accurate.
        (2) Causality is inviolate aka time travel isn't possible
        (3) FTL is possible
        Personally I don't know that I'd bet my soul on any of them.

      • by pz (113803)

        You cannot have entanglement without interaction, you cannot have interaction between two things that lie outside of each other's light cones.

        My extremely fuzzy understanding from freshman physics is that the universe is thought to have undergone an expansion early on that was, indeed, faster than light. That post-big-bang period was called "inflation", an idea Dr. Alan Guth came up with (and he happened to be my freshman physics lecturer). So it is possible that two systems that became entangled prior to inflation are now outside each other's light cones.

      • What about wormholes? Maybe there are dimensions where you can travel at below light speed and get there before light traveling in normal space makes the same trip the long way.
      • by gzuckier (1155781)

        The catch being that the scoring of whether there is interaction is done in your brain, which is halfway between the two events, and certainly small enough to allow for interactions between the perception of the one event and the perception of the other event.
        that would be one tricky universe though.

    • All experimental evidence suggests that the transfer of information faster than the speed of light in a vacuum is impossible. Scientists understand full well that there is always a possibility some new discovery could upend even the most fundamental view of the universe, but until evidence to suggest otherwise comes along, scientists can only work with the experimental data they have -- and so far, all of that suggests FTL transfer of information is impossible.

      Therefore, drawing from the incredible amoun
      • If the scientists free will in choosing the settings of the detectors can't be trusted, how can their free will in choosing the quasars that will choose the settings of the detectors be trusted?

        • Because there cannot be casual information communication between a star of that distance and something on the Earth. In otherwords, there cannot be conspiracy between two things which are physically incapable of communication.
          • Right, but the scientists decision to use a certain set of quasars could be influenced just as much as their decision to set the experiments parameters a certain way could be.

            • But the conspiring forces can't know what the quasars are sending off! That's the point. Nothing is capable of containing information pertaining to what the quasars have sent, because it's impossible to have made a round trip to find out ahead of time. Therefore, even if the forces can influence the scientist's choice of quasar, the mysterious force still has no idea which quasar will say what, so it can't rig the experiment.

              As an analogy, imagine there are three settings: A, B, and C. The mysterious for
    • by clovis (4684)

      Turns out that if I had read the pdf to the end, I would have seen that they discussed the alternate expected outcome's implications in detail.

    • by iggymanz (596061)

      think about the electric fields (other fields exist, just as example) between all particles, they have always existed, for 13.8 billion years. photons are just vibrations in that field. so everything was and continues to be entangled

  • by Anonymous Coward

    ...back into the past to warn us that the Beta is a bad idea!

    Why won't Dice listen?

  • What is it?
  • Superdeterminism (Score:5, Insightful)

    by Warbothong (905464) on Friday February 21, 2014 @12:24PM (#46304357) Homepage

    While interesting, it doesn't solve the most glaring assumption of Bell's inequality which is that the Universe is non-deterministic.

    It's perfectly plausible that the Universe is deterministic, and hence the behaviour of the particles *and the experimenters* is pre-determined, ie. there is no choice in which measurement to take. Taking the determinism of the observers into account tends to be called "superdeterminism", and is necessarily a global property: either the whole Universe is superdeterministic, or nothing is deterministic. Bell's inequalities demonstrate this, since they cannot be explained by a *local* deterministic model, ie. a model which only involves properties of the particles (known as 'local hidden variables').

    Note that superdeterminism doesn't necessarily rule out 'free will'. Personally I find the most elegant explanation of free will to be irreducibility: an irreducible process has no 'shortcuts'; the only way to predict its result is to run the process from start to finish. If, say, my mind is a deterministic but irreducible process, then a powerful-enough computer could predict my decisions exactly. However, I can still be said to have 'free will' because the computer can't take any shortcuts in its calculations: the only way it can predict my decisions is to run a perfect simulation of me and see what decisions that simulation makes, but in that case it's still (a perfect simulation of) 'me' making the decisions.

    • by Progman3K (515744)

      I really like that, man.
      I'm not peer-reviewed, so it doesn't matter, but I like your idea

      • I really like that, man.
        I'm not peer-reviewed, so it doesn't matter, but I like your idea

        I didn't come up with it BTW ;)

        Superdeterminism is a widely-known term in Physics, eg. see http://en.wikipedia.org/wiki/S... [wikipedia.org]
        Irreducibility isn't as common, and it seems to go under various different names ("irreducibility" is the term used by Wolfram, eg. http://en.wikipedia.org/wiki/C... [wikipedia.org] ) and it seems to get 'discovered' over and over, eg. this ./ article from last year http://science.slashdot.org/st... [slashdot.org]

        • by Progman3K (515744)

          Thanks! So that would mean that it is more likely that our universe is a simulation, right? Determinism would sort of imply it, since it can't play out any differently.

          The way I've thought of it would be that it is theorized our universe is inside a black-hole; all space and time perceived is an illusion because it is all happening at the same time, in the singularity, making non-locality trivial to implement. I suppose the flaw is that you need multiple dimensions at right-angles to it to make sense of it.

    • I knew you were going to say that.

    • Re:Superdeterminism (Score:5, Interesting)

      by jfengel (409917) on Friday February 21, 2014 @02:17PM (#46305047) Homepage Journal

      Yeah, superdeterminism was my first thought in reading this. It sounds like they're pushing any superdeterminism all the way back to the time of inflation, but since that's exactly what superdeterminism would predict, I don't see that they've contradicted anything.

      It's intellectually unsatisfying to think that superdeterminism could relate to something as supremely complicated as a scientific apparatus: the whole state two measuring apparatuses conspires to yield opposite results on particles that were, up to that instant, completely identical, without any communication. But I think it makes more sense than trying to impose some outside "free will" force that also makes itself visible only on the most carefully isolated particle experiments yet also just happens to manifest as something we see numerous orders of magnitude larger as "what we think", despite layers of purely chemical interactions in between.

      We're still obligated to explain the larger-scale version of "free will", in that the phenomenon that we believe it exists is real, and I think your way of looking at it is good as any. And superdeterminism doesn't contradict that.

      Superdeterminism still doesn't satisfy, but I suspect that "satisfaction" is a purely human property. The equations yield the right answers, and that's all you get. Like classical dynamics, free will is an idea that we're going to keep expecting to see, even though we'll always get out unsatisfying answers when we try to explain corner cases.

      • It's intellectually unsatisfying to think that superdeterminism could relate to something as supremely complicated as a scientific apparatus:

        Why do you say that? If the whole universe is deterministic, then of course every part is deterministic. A scientific apparatus is incredibly simple compared to the universe as a whole.

        Perhaps what you mean is that you want to know what mechanism creates the appearance of randomness/entanglement/free-will in a fully deterministic universe? Why does it appear that your actions have an influence on distant events, and that influence takes the form of a certain type of correlations between observables? It

        • by jfengel (409917)

          The problem is that it's hard for me to conceive how, early on in the universe, the particles that would eventually make up my measuring apparatus and the particles that eventually make up your apparatus went their separate ways, in such a fashion that at a particular time they'd interact with two identical entangled particles and give opposite results. It's such a complex thing to achieve such a simple result.

          Not that there's anything wrong with that, if that's where the universe happens to lead us. It is

    • by Khashishi (775369)

      But, wouldn't a rock have free will under that definition? Well, it depends on what you consider a decision to be. Everything is irreducible to some extent. You can get a pretty good approximation of the behavior of a rock by considering a idealized spherical mass, but to get more precise, you need to add more detail. For a perfect account of the behavior, you need the full quantum state of the system.

    • "Note that superdeterminism doesn't necessarily rule out 'free will'."

      I guess I don't understand how the example that you gave following that statement supports the idea of "free will." For me the more interesting question is: "What does awareness mean in a deterministic world?"

      Are we just observers riding the deterministic "roller coaster?"

    • Perhaps the Universe is deterministic and the results are pre-determined. Or what if the many worlds theory is correct and any worlds where the results of the experiment don't square up are the worlds that cease to exist. We would always find ourselves in one of the branching worlds where the results of the quantum experiments match in the same way as if the detectors were tuned for those results.
      • Does the following make any sense?

        My thinking was that if two far-away detectors measure an entangled pair of photons (e.g.), each detector will measure both possible results (e.g. up *and* down). Each detector and thereby their environment becomes entangled with that photon. So each detector and it's environment starts a new branch in their respective many-worlds reality. (One side of the branch for “up” and one branch for “down”).

        When you later compare the measurements of the
  • > "implies that a physicist running the experiment does not have complete free will"

    There is no such thing as free will in the old philosophical sense. There is just determinism with (potentially) true quantum randomness. The latter could be based on a deeper determinism, but that is exactly the kind of "reality" Einstein didn't want to gove up on -- real things out there with real, measurable properties. Quantum mechanics based on an even deeper determinism would doubly violate this principle by shov

    • Heh......

      "The wise old philosopher finally proved that there was no such thing as free will. What did he do next? Whatever he wanted."
    • You are neglecting the possibility of true dualism -- that we have a soul. If a portion of our decisions comes from an extra-universal source that does not follow the deterministic rules of the universe, that would provide us with true free will. Sadly, such a thing may be innately non-provable.

      • by Khashishi (775369)

        That would be considered a "hidden variable" theory. For this soul theory to be able to explain quantum mechanics, the soul must have some faster than light communication.

  • by Remus Shepherd (32833) <remus@panix.com> on Friday February 21, 2014 @12:31PM (#46304409) Homepage

    A year from now you should expect to hear about this research again, but it will be delivered as a dramatic result: "Scientists have proven Free Will exists!", or "Scientists have disproven Free Will!" The experiment won't actually do this, but that's how the press will report it.

    The thought that some hidden variable may affect not only both sides of the universe but our own minds is frightening. It would really shake things up. So I expect that QM and 'free will' will come out triumphant in this test. Whether it's an actual assessment of Free Will or not will be the interesting argument afterward.

    • by TheCarp (96830)

      I am kind of hoping they will close the loophole and find the equality is still violated. If so, then i actually expect the headline "Do far away stars disprove quantum mechanics?"

    • by Immerman (2627577)

      As it is classical physics had already ruled out the possibility of free will centuries ago, and QM only inserted a bunch of dice-rolling that could give the illusion of it. For free will to actually exist we must assume some sort of non-physical "soul" that can manipulate the outcome of the dice.

      Theoretically at least we could monitor every quantum effect that influences the brain and look for statistical anomalies, but even if no anomalies were found that wouldn't rule out free will - rolling 2,5,3 is st

      • by lucien86 (917502)

        As it is classical physics had already ruled out the possibility of free will centuries ago, and QM only inserted a bunch of dice-rolling that could give the illusion of it. For free will to actually exist we must assume some sort of non-physical "soul" that can manipulate the outcome of the dice.

        Have to disagree with you there, by the definition that I know that free will is a Turing Machine classical physics certainly doesn't stop it or rule it out.. It is only General Relativity with its fixed past and potentially fixed future that really disallows free will, but then if General Relativity is correct the universe basically doesn't exist anyway so the question is pretty moot. :)

        • by Immerman (2627577)

          I have never heard such a claim (Turing), and I would contest it strenuously. A Turing machine is a deterministic device - with a given input there is exactly one outcome possible. You may not be able to say for certain that any given input will eventually terminate beforehand, but give a billion machines the same input and they will all proceed in the exact same fashion, with no possibility of expressing free will.

          And operating under classical physics the entire universe is deterministic - if you could s

          • by lucien86 (917502)

            Oh dear! The way we operate Turing machines they mostly do behave as deterministic devices but just go and try injecting a little noise into the system, even the tiniest amounts - they certainly do not behave as deterministic devices then. In fact if you try to calculate the size of a computers potential state space it is so large that it is effectively infinite (maybe ~10^10^10^10^10) yet the actual physical state at any one time will only be a few points within that space and this ratio means that compute

            • by Immerman (2627577)

              Yes, if you inserted random noise into a Turing machine it would no longer be deterministic. It would also no longer be a Turing machine, because it would no longer reliably run the software you installed - which is the whole point.

              Besides which, in a clockwork universe there is no source of random noise, bug, or errors - all noise is perfectly predictable given only the initial state of the universe. And there is no observer required for the determinism implied by classical physics - it's simply a recogn

              • by lucien86 (917502)

                Sorry I disagree, Newton uses time as a purely abstract notional concept. In Newton there is a single reality and a single time that is physically real, and the past and future are merely extrapolations from that point. General Relativity is fundamentally different in that the overall structure of space is 4 dimensional and the past and future co-exist directly with the present.
                As for wormholes - firstly to enter a wormhole you must cross over an event horizon which itself is an FTL barrier. Also the way w

                • by Immerman (2627577)

                  That is a very "interesting" reading of Newton. How do you measure time reliably if time is not real? And without being able to measure time reliably all of Newtonian physics breaks down. Newton said that space provided absolute and invariant separation between things, and time provided absolute and invariant separation between events. GR simply opened the realization that space and time are interwoven, and that depending on your reference frame you can exchange separation in space for separation in tim

                  • by lucien86 (917502)

                    I am not saying that time is not real merely that the part that is real is point like, the rest is treated as an abstract dimension. It is quite acceptable in Newton to plot a graph of motion against time and in fact many units (like speed) depend on division by time but it is always understood that the time line itself is an abstract thing - extracted from reality. That's the way I was taught it in school. Think of the face of a clock, the circle represents a part of the abstract time line but the hands on

                    • by Immerman (2627577)

                      I think your teachers didn't really understand what they were talking about. I would say rather that GR simply makes "now" a much more complicated concept than in Newtonian physics. At any given point in space, time is still presumed to behave as it does in Newtonian physics. The fundamental difference is that GR recognizes that you can't change your reference position and velocity in space without also changing your position and velocity in time - the two concepts are interwoven rather than being indepen

  • by Jim Sadler (3430529)
    For quite a few people with either religious or unusual beliefs there is a belief that the nature of reality or actuality can not be penetrated as a designed law installed by a creator. If it is simply an advanced race and we are living in their simulated universe or whether if is God that intends for us to live within a perpetual mystery the end result is the same. Humanity will never be allowed to understand the nature of things. There is also some belief that only after death are we allowed unde
    • by lucien86 (917502)

      This is why the scientific study of the 'psychic' is probably the most controversial and 'dangerous' area that science has ever touched. Imagine if science had discovered that the psychic was real then used reductionism to reduce it all to first principles and logic and ultimately physics. It would literally be the end for religion, the death of mysticism and a direct confrontation against the nature of 'God'. Even worse imagine that 'God' becomes a technology - created and manipulated in the lab, used to b

  • I did write a blog post about quantum mechanics and the “free will theorem” at the time.

    http://stephan.sugarmotor.org/... [sugarmotor.org]

    I think this new development isn't covering all possibilities there

  • "a scenario that, however far-fetched, implies that a physicist running the experiment does not have complete free will in choosing each detectorâ(TM)s setting."

    Of course the physicist doesn't have free will. No one has free will. If the universe is controlled by natural laws everything that has happened or ever will happen must be preordained. Every synapse that has ever fired in our brains is just an electrochemical event caused by a long chain of other events that can be traced back to the big ba

    • >Of course the physicist doesn't have free will. No one has free will. If the universe is controlled by natural laws everything that has happened or ever will happen must be preordained. Every synapse that has ever fired in our brains is just an electrochemical event caused by a long chain of other events that can be traced back to the big bang. That is assuming that natural laws actually are complete and consistent. But why would this be true of natural law, when it is not even true in mathematics? ht [wikipedia.org]
  • Is this perhaps a form of Anthropic Principle? Universe instances where Experiment X is a deadly no-no get annihilated such that nobody is around to witness Experiment X take place to completion.

    Considering how many hair-raising Cold War near-misses we've had, I wonder if AP is not involved. Between the Cold War and LHC, we may be running out of universe instances :-)

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