Banner
    Quantum Entanglement Without Spooky Action At A Distance?
    By Hank Campbell | June 24th 2011 11:30 AM | 31 comments | Print | E-mail | Track Comments
    About Hank

    I'm the founder of Science 2.0®.

    A wise man once said Darwin had the greatest idea anyone ever had. Others may prefer Newton or Archimedes...

    View Hank's Profile
    Quantum entanglement was strange when it was conceptualized.   It violated Einstein's famous speed limit in his Theory of Relativity and he called it spukhafte Fernwirkung - “spooky action at a distance” and sought to note the flaws in Heisenberg's uncertainty principle and the Copenhagen interpretation.   The result was the Einstein–Podolsky–Rosen paradox.

    Since that Golden Age of theoretical physics thought experiments, much has changed.   In 1964, John Stewart Bell showed how the principle of locality, one of the key assumptions in the EPR paradox, conflicted with quantum theory and the upper limit on the strength of correlations that can be produced in any theory obeying local realism became Bell's inequality (we have too many articles on quantum mechanics for a narrow-enough search that will provide quality results detailing QM and EPR and Bell more thoroughly so results for Alice and Bob make more sense, as you will see if you read them).

    Asher Peres, a quantum information theorist, once remarked jokingly in a letter to a colleague, Dagmar Bruß, that "Entanglement is a trick 'quantum magicians' use to produce phenomena that cannot be imitated by 'classical magicians'. When two particles are entangled, measurements performed on one of them immediately affect the other, no matter how far apart the particles are. What if, in an experiment, one considers a system that does not allow for entanglement? Will the quantum magicians still have an advantage over the classical magicians?"

    A team of physicists recently sought to tackle this 'magic' question. They used a qutrit – a classical trit (a base-3 digit) that can exist in three possible states, basically a 3-D version of the better known qubit - consisting of a single photon that can assume three distinguishable states - and, they write in Nature of their experiment showing a system which does not allow for entanglement and still found results which cannot be interpreted classically.  
     
    "We were able to demonstrate experimentally that quantum mechanical measurements cannot be interpreted in a classical way even when no entanglement is involved," said Radek Lapkiewicz from the Vienna Center for Quantum Science and Technology at the  University of Vienna. 


    The central part of the optical setup used to demonstrate that even a system which does not allow entanglement exhibits features commonly attributed to this phenomenon. (Credit: IQOQI; Jacqueline Godany 2011)

    Quantum physics is not magic - but like that owl in the Tootsie Pop commercial, the magic number may be three

    Quantum physics, to laypeople, makes little sense because it often contradicts what we perceive and experience and understand as classical physics.  If we go into outer space and look at Earth, from our point of view we see only one hemisphere but as the Earth spins around its axis we can 'construct' an accurate picture of the total planet.  We assume the shape of the continents stays the same, even while we cannot see them. 

    That's classical physics - experience and assumptions allow us to assign properties to a system without actually observing it. 

    That's not the case in a "quantum Earth".  Unlike the planet we would see from space, where the various pieces fit together as they do in a puzzle, the pieces of the quantum Earth do not appear to fit together.   Not all all its properties can be simultaneously well-defined.

    Yet the pattern is not random: it is possible to predict by how much the individual parts will differ from each other after an observation.  Confusing?  Well, yeah, but that's why it seems like magic.

    The 'magic number' may be three, the researchers say - a single three-state system (that qutrit again) is the simplest system in which the contradiction is possible, because a three-state system is indivisible. 
    Our experimental results are in conflict with any description of Nature that relies on a joint probability distribution of outcomes of simple set of measurements. This also precludes any description in terms of non-contextual hidden-variable models. 
    ...
    Our result sheds new light on the conflict between quantum and classical physics. To finish, we want to point out that any model-based on a joint probability distribution can in principle be non-deterministic.  The experimental preclusion of such models highlights the fact that even for a single, indivisible quantum system, allowing randomness is not sufficient to allow its description with a conceptually classical model.

    Or, if the owl makes more sense to you:



    Read more about their photonic qutrit experiment, though it will cost you $32:


    Citation: Radek Lapkiewicz, Peizhe Li, Christoph Schaeff, Nathan K. Langford, Sven Ramelow, Marcin Wieśniak&Anton Zeilinger, 'Experimental non-classicality of an indivisible quantum system', Nature 474, 490–493 (23 June 2011) doi:10.1038/nature10119

    Comments

    Yes this is correct....the Father, the Son and the Holy Ghost....

    Hank
    ha ha...very nice.  I had not made that connection but science simply wants to explain the universe according to natural laws and the spark of life can certainly be open to interpretation by thelogians and the faithful, so sure.
    Unknown unknowns.

    Bonny Bonobo alias Brat
    I like this article Hank but unfortunately the more I read about quantum entanglement the more entangled I become and the less I understand. Still, I plan to keep reading everything I come across on this subject here and hopefully one day I will find enough coherent decoherence to disentangle myself from this quantum superposition and its superdense coding. Could someone please write a 'Quantum Entanglement for Dummies' blog?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    ujm
    Once Quantum Entanglement for Dummies has been written, someone has to write "Quantum Entanglement for Dummies for Dummies". This is also known as the "von Neumann catastrophe of infinite regression".
    Bonny Bonobo alias Brat
    Ulrich, can you please shed a bit more light upon Von Neumann's catastrophe of infinite regression?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    ujm
    I was joking. Von Neumann's catastrophe is somewhat related to the above regress or recursion, but the name for the latter is still up for grabs. Here is a decent explanation of the former. Essentially, if you construe quantum mechanics upside down or inside out (which is to say the wrong way), you begin by imagining a highly contagious superposition (say of "spin up" and "spin down" with respect to a given axis). If you now perform a measurement designed to reveal whether the spin is up or down, the apparatus gets infected by the superposition superbug, so you need another measurement designed to show you what the first apparatus indicates. But then the second apparatus gets infected as well, so you need a third apparatus, and so on ad nauseam. That's the von Neumann thing.
    Hey, come on. Not everyone here is a physics grad!

    Let's start at the beginning and assume (pace Sascha) that there is a reality out there. Call it the zeroth order. You make an observation, this is a first order observation. Which is fine in the classical picture but falls apart in QM because there is no consistent description of reality that doesn't have to be changed depending on what you decide to measure. It begins to get noticable with interference fringes. Photons are nice little localised particles, except that they pass through two slits at once. That gave us 3/4 of a century trying to make up our minds what wave/particle duality means. Then along came Bell the theorist and Aspect the experimentalist and proved that it applies to systems, not just individual particles. You can't regard two particles as two separate particles, they are one system. What's more, if you decide that you're going to measure, and thus fix, one parameter, say the amount of horizontal polarization one photon has, its partner, now miles away, jumps to the same tune.  QM, of course, "works" and is applied in all sorts of technology, sometimes explicitly, sometimes without people realizing it. Meanwhile in the background, Schrodinger's cat is still half alive and half dead, though nobody wanted to believe that so they made up stories about observers collapsing the wave function. But Schrodinger's friend, Wigner, had already thought of that so he added another player, "Wigner's friend", Wigner himself being the mad scientist. Wigner may determine the fate of the cat by having a look, but supposing the friend hasn't observed Wigner? Doesn't that mean that the cat plus Wigner are in just as much a superposition as far as Wigner's friend is concerned as the cat was as far as Wigner is concerned? That's a second order observation by the way, Wigner's friend observing Wigner observing the cat. Obviously this can go on forever and while we're about it we may as well have the cat in on the act and observing Wigner's friend.

    This is why it's called a cat-astrophe.

    Catastrophe is a mathematical term for an unwanted infinity. However it is, if I understand Sacha correctly, not a catastrophe for our understanding of reality but the solution to most of the quantum conundrums that exercised everyone for much of the 20th century. The big question is then whether we have to deny all absolute reality or just say it'll turn out to be a mathematical artefact. One day.

    If this is total rubbish, feel free to delete it, I'm just trying to give people an easier picture to digest than talk of "superposition superbugs" which I can't make any sense of, myself. "Woo-woo, I'm a superbug!"   No, that still doesn't help.  :(
    I'm with Helen...this should be made to sound more like science,less like religion. Where's the "law" of conservation of photons? Were we to say we split a hydrogen nucleus in two and got two hydrogen ions, what would that mean in terms of conservation of mass/energy? E=Mc2/2? x2?

    vongehr
    Hank - why the hell this totally misleading title if the research is clearly (almost the most important point) that there is no entanglement necessary? Did you learn nothing from my articles where I spend hours and hours to get it down to the lay level just so you do not have to? ;-)
    Hank
    Was I being too clever?  They have a system which does not allow for entanglement but got results that can't be interpreted classically.  How would you title it, other than 'Experimental non-classicality of an indivisible quantum system'?  I don't think anyone would read that.   'Spooky action with no entanglement'?

    Actually, "New! Improved!  Spooky Action - Now With Less Enganglement!" might have been pretty good.   Especially if I created a graphic that looked like a box of detergent.
    vongehr
    "can't be interpreted classically"
    Since the orientations are not selected after the photon is already on its way, there is indeed, as you correctly point out, no "spooky action at a distance". In other words, there would not be a problem for the photon to already know the orientations of all the wave plates (the angles) beforehand and thus carry hidden variables along that tell it exactly where to go at each turn. Thus, it is not true that this experiment cannot be interpreted classically! It would be certainly very silly to do so, of course, but that never stopped the religiously believing in naive reality from interpreting everything in conspirational ways as long as holy direct realism is saved. So, in my point of view, a very nice experiment, but not a substitute to the usual EPR/Bell/Aspect issue, which actually proves that no classical model is possible at all, however silly it would be.
    Sascha, good point - a local realist "save" of the common Bell experiments with two entangled photons (as segue to make the point) would be silly, even if we could in principle imagine some sort of unusual local realism. However, I'm not sure what you're getting at, re no problem for photons to "know" filter settings. The filters are distant entities, the photons are supposed to have definite states in realist ideas, and the two should simply interact locally when they do at all. Photons are supposed to have a specific chance of passing given polarization filters anyway, according to the common rule of cos² θ. Various bizarre rules proposed to see if a LR specification *could* pass the inequality tests, aren't consistent with that behavior.

    It's easy to consider: even if the source emits photons of randomly varying but matched "real polarization angle" per local superposition relations, their chance of both passing identical distant filters is less than half (3/8, in my BOTE estimation.)

    Well, if the results for three particles can't be explained classically (or, in any reasonable facsimile thereof) even *without* entanglement, in such case the post should instead be titled, "Spooky Action At A Distance Without Quantum Entanglement?" Since most people find oddball attempts to preserve realism to be weirder than just leaving it all mysterious, maybe it's better to accept that we've probably got SAAAD.

    BTW, does anyone here think Bohmian mechanics can work and save any of this? I am very skeptical ...

    vongehr
    no problem for photons to "know" filter settings.
    In this experiment the photons can "know" about the filter settings during their creation, thus contextual hidden variables are not ruled out, and thus this experiment is no proof against classicality. Only the Aspect experiments (those that select the angles after the photons have been created) do falsify also contextual hidden variables under the assumption of micro causality (light speed limit) and thus do disprove classicality. It is explained a little more here (in relation to this new experiment above) and here (the accepted actual proof against classicality on a lay level).
    "Only the Aspect experiments (those that select the angles after the photons have been created) do falsify also contextual hidden variables under the assumption of micro causality (light speed limit) and thus do disprove classicality."

    Since when has it been possible to make a selection without using equipment that has been thoroughly entangled since the beginning of time?

    As you know, I have a bee in my bonnet about this. The BB was an incredibly unlikely event, if, in fact, it is just one member of an eternal equilibrium ensemble. The probability of the existing universe fluctuating into a time-reversed (Planck) BB gives some idea of the probability, but that's what BB cosmology requires unless there's some Harry Potter stuff going on.  Such an event would require all the delicate equipment we have assembled, all the entangled photons, you, me and Schrodinger's cat all to fluctuate into a Planck point - no excuse for a few photons "missing". There might be googolplexians of attempts which just fail at the last (anti-first) particle. (See my second blog - planned after my first one - planned "soon".) Probably the most likely trajectory would take 13.7 billion years. Or perhaps that should be called -13.7 billion years. But the final state of this time-reversed universe would still have all the information of the actual universe in it. Why is the forwards universe unlikely to have had exactly as much information in it when it set out? All the entanglement you could ever want, to ensure that all our delayed-choice experiments are no such thing. And, in answer to why that particular, fine-tuned state*, I'm just saying that reversing the universe makes it go through a deterministic trajectory back to the time-reversed BB. In this unlikeliest of all unlikely universes (actually a dead-heat with our own) entanglement doesn't anti-start at some point, it persists back to the anti-beginning.

    * that would be a "why not?"
    vongehr
    The BB was an incredibly unlikely event, if, in fact, it is just one member of an eternal equilibrium ensemble. The probability of the existing universe fluctuating into a time-reversed (Planck) BB gives some idea of the probability, but that's what BB cosmology requires unless there's some Harry Potter stuff going on.  Such an event would require all the delicate equipment we have assembled, all the entangled photons, you, me and Schrodinger's cat all to fluctuate into a Planck point
    Wow - I have no idea what you are talking about, but it is sure nothing to do with modern cosmology as far as I can see. Did you look at chaotic eternal inflation? How is the BB unlikely if it happens all the time?

    Of course I've heard of chaotic eternal inflation. The word chaotic begs the question for a start - information out of nowhere? But hey, what is a little bit of information compared with an infinite entropy pump powered by an infinite supply of energy? That's Harry Potter physics.

    What I said was "The BB was an incredibly unlikely event, if, in fact, it is just one member of an eternal equilibrium ensemble". If, in fact, it is just about as far away from an equilibrium ensemble as you can get then obviously the probability is unity. I don't see the difficulty.





    So did anyone yet say that this is just god rolling dice or testing us?

    It's just God rolling dice or testing us.
    ujm
    When two particles are entangled, measurements performed on one of them immediately affect the other, no matter how far apart the particles are.
    That's the way it's usually put by science popularizers, but it commits a serious error of omission, as standup Doug would call it. Fact of the matter is that the outcomes of measurements performed on two entangled systems (one on each) are correlated. If the outcome of one measurement affects the other particle in the absence of a measurement performed on the other particle, we know nothing of it. Least of all can we say that it is "immediately" affected, and this not just because simultaneity is a feature of the language (the coordinate system) we chose to describe a physical situation rather than an objective feature of the world.
    Ulrich, you are right about how Copenhagen views the situation - "correlated" with no clear insight into "what's really there" meanwhile before measurement. But for example in de Broglie-Bohn theory (pilot wave), there is an actual influence. I don't take dBB very seriously but some physicists do. They also have the problem with standards of simultaneity, which I think they dodge in clunky fashion reminiscent of how MWI enthusiasts evade the increase in net total mass-energy of the state (regardless of excuse given for we we "can't see the other branches"), why don't objects just crash into each other (incoherent before anyway), etc.

    M. reza Tirtgan

    In case ofparticles entanglement the spooky action at a distance similarly to Newton gravity action at a distance exists. In Einstein’s GRT the action at a distance also exist in a different manner, i.e. a mass-body curved the space-time spontaneously up to infinity. If this mass moves to another place, i.e. place A to B, this curved space time spontaneously taken place for B location. The entanglement or correlation of particles is confirmed by Aspect experiment. While, a photon pair emitted by a source is traveling in vacuum medium at c speed, the measurementof spin of photon of the pair by a measuring device, e.g. its spin up, has an instantaneous effect on the spin of other photon pair e.g. spin down. Therefore, an interaction is transferred at super-luminal speed. According to Hparticle-paths hypothesis in site Hparticle.com/, the correlation is down by contracton releasing, a particle that can be traveled spontaneously within abstract vacuum of a tunnel (an alternate to wormhole) that link the photon pair. As the result, there is two ways of signal transfer:

     1) In spatial medium at maximum speed c.

     2) Within abstract vacuum of a tunnel(alternate to wormhole)in spatial medium instantaneously, i.e. the famousspooky action at a distance, via contracton transfer.

     In case of gravitational interaction the same scenario as in case 2 is taken place via contracton transfer within the abstract vacuum tunnel.

     

    Tirgan
    Halliday
    M. Reza:

    You appear to have a significant misunderstanding of Einstein's General Relativity theory (GRT):  Namely, you claim that "In Einstein’s GRT the action at a distance also exist in a different manner, i.e. a mass-body curved the space-time spontaneously up to infinity. If this mass moves to another place, i.e. place A to B, this curved space time spontaneously taken place for B location."

    The truth is quite different:  "A mass-body curve[s] space-time" only locally, and this curvature causes further local curvature of space-time in such a way as to propagate at a finite velocity (c, for sufficiently small perturbations).

    In fact, it is because of this non-instantaneous change, with a change in position of a massive body, that GRT has such things as Gravitational Waves.  Ever heard of those?

    So, no, there is no similar "action at a distance" within GRT.

    David
    M. reza Tirtgan

    Dear David

    Thanks a lot for your comment, the following is my reply:

    1) Contrary to the case of photon, there is no aberration in case of gravitational field potential (orexpandons), Sec. 5(2)1d, part D of Hparticles.com/

    2)“If gravity from the Sun propagated outward at the speed of light, transmission delay would progressively increasethe angular momentum of bodies orbiting the Sun so great a rate that orbital radii would double in 1000 revolutions” Tom Van Flandern Articles http://Idolphin.org/VanFlandern/

    3) “The force is the instantaneous gradient of the retarded potential”, “Potential cause force or force cause potential. The geometric interpretation of GRassumes the former” http://metaresearch.org/home/viewpoint/Kopeikin.asp Third Round of Responses”“Disturbances of this potential field or medium are called gravitational waves. According to GR such wavespropagate at the speed of light, as do all other phenomena associated with potential field that that propagate at all”. “However, the name not withstanding gravitational waves have nothing to do with gravitational force. Binary pulsars (with masses and speeds) show that the speed of gravity must beat least 20 millions times the speed of light. A 1997 laboratory experiment by Walker&Dual showed gravitational signals propagated much faster that light signals”. “Propagation delay is not important for gravitational potential because the potential field is already present near anysource mass, and does not propagate to get there. Its shape is describe byEinstein’s equations" Flandern, T.V., Meta Research, Kopeinkin and the speed of gravity”14/1/2004 the physical meaning.

    4)  At present, the gravitational wave is not proves experimentaly despite of satellite testing  this tests and theoretically interpretation by GRT.5) According to Hparticles.com/, in our expanding universe we must to accept two kinds of velocities in spatial medium, A) the propagation of particles, and field potential at maximum c speed within normal vacuum. B) the propagation of interaction, e.g. gravitational, electromagnetical, entanglement, via contracton transfer within abstract vacuum in tunnel (alternate to wormhole) spontaneously. For this reason, we can detect the retarded wave in normal vacuum medium. Thus, we cannot detect experimentally the advanced waves based on Maxwell equation solutions in electromagnetism. 

    Tirgan
    Tirgan
    quantropy
    For those of you who don't have $32 5o spare at the moment, the cited paper is also available on arxiv http://arxiv.org/abs/1106.4481
    I don´t quite see why this phenomena is so amazing, i think it´s just peoples imagination that makes it look complicated. Reality is simple. There´s no action at a distance. When particles interact they simply become synchronized in their local motion.. So if you measure one particle, you can reckon the state of it´s 'pair', a particle it shared it´s motion with. NO ONE EVER SHOWED THAT THERE'S ACTION AT A DISTANCE, IT WAS NOT EVER EVER IN HISTORY OF UNIVERSE PROVEN THAT AFFECTING ONE PARTICLE AFFECT THE OTHER. THERE'S NO SUCH THING AS ACTION AT A DISTANCE. So before it confused more people, let´s just rename it from quantum entanglement to quantum synchronization or alignment or something else more realistic.
    The reason why entanglement is a source of mirth to physicist is not due to action at a distance(which doesn't exist), but due to the states those particles can have, those states cannot be explained with laws of classical physics. In fact this is the whole reason why quantum physics had been established, the way those particles move and convert from one form to another is quite otherworldly. People who believe in action at a distance should give up physics and become science fiction writers...

    havent they proved that entaglement does exist?
    The Fabric of the Cosmos:
    Quantum Leap
    Airing Wednesday
    November 16 at 9pm ET on PBS
    (Check local listings)

    The difficulties that theorists encountered at the present time are standing beyond the red lines imposed by GRT , SRT& QFT. There is an afraid passing these red lines to reach new idea respect to the rest of physical community just during 90 years. There are experiments and tests that contradict the foundation of these two theories. Nevertheless are rejected by them. One of them is entanglement that is rejected by EPR paradox based on SRT. The entanglement is confirmed by Aspect experiment based on Bell inequality. It is along with an important law behind. According to H-particles hypothesis in related sites the correlation is down by contracton releasing, a particle that can be traveled spontaneously within abstract vacuum of a tunnel (an alternate to wormhole) nominating H hall package tunnel that link the photon pair. Moreover, the interaction such as gravitational and electromagnetical are down are down via these tunnels instantaneously that are nominating spooky action at a distance. In other words, there are two kinds of propagation in spatial medium, 1) the particle travel equal or less than light speed, the signal and potential propagation at light speed. 2) The force propagation, e.g gravitational and electromagnetical, at superluminal speed via H hall tunnel.

    Again,how about "law" of conservation of mass/energy?
    Were one to say we split a hydrogen nucleus and produced two hydrogen ions, one might expect a question about loaves & fishes? We need less of the sound of religion, more the hum of science. Where is the conservation of photons?
    E=Mc2/2? x2 ?

    Johannes Koelman
    Hank, I hope you didn't pay $32 to get access to this taxpayer-funded piece of work. Rightly so, the authors did make their preprint freely available.

    For those struggling with spooky entanglements and their consequences, see here. (The fact that in this blogpost the spooky chest of quantum drawers measures 3x3 is not coincidental, three is the magical number.)

    Hank
    I didn't spend the $32, I get them under embargo, but since you found the handy preprint, I will edit the article link.