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George and John’s Excellent Adventures in Quantum Entanglement [Video]

The views expressed are those of the author and are not necessarily those of Scientific American.

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Simply put, bottomlessly deep: that is the definition of a great discovery in science. From the principle of relativity to evolution by natural selection, the concepts that govern our world are actually not that hard to state. What they mean and what they imply—well, that’s another matter. And so it is with quantum entanglement. One of the most important discoveries ever made, entanglement is fairly straightforward to describe, but has yet to be understood in any serious way. Physicists have barely even gotten over their amazement that the phenomenon even exists.

The two-part video that I put together with my colleagues John Matson and Mary Karmelek, working with Sci Am‘s film guru Eric Olson, dramatizes entanglement. Part one presents it metaphorically; part two will show the real McCoy in a physics laboratory. The film follows in the footsteps of a steady progression of simplified versions of the original scientific arguments that has taken place over the past several decades. Not only has the theory been streamlined, so has the experimental apparatus. It could now fit on a living-room end table and should soon become a standard exercise in college physics-for-poets classes.

The basic point of entanglement is that the behavior of objects at spatially separated locations is random yet coordinated. Two (or more) particles behave as a single indivisible system, no matter how far apart they are. Indeed, even to speak of “particles” in the plural is a falsehood; we see them as individual parts, but they possess collective properties that cannot be partitioned. In the 1930s, Albert Einstein argued that for entangled particles to behave in such a coordinated way, either their behavior must be choreographed in advance or they must surreptitiously influence each other on the fly. This influence cannot pass through the intervening space—it would be, as Einstein put it, “spooky action at a distance.” Three decades later, physicist John Bell devised an experiment that rules out the first possibility, leaving the spooky one as a creepy fact of nature.

The first two card tricks in the video show the basic thought-experiment that Einstein devised and published in a famous paper with Boris Podolsky and Nathan Rosen. The third trick shows Bell’s elaboration. His basic insight was that it’s easy enough to choreograph a simple pattern of behavior, but impossible to prearrange a sufficiently complicated one. By the way, you can use Bell’s approach if any of your friends ever claims to be psychic. Ask the right types of questions, and no one will be able to respond unless they really are psychic. Humans, of course, aren’t. But particles do have a telepathic power, albeit of a very limited sort.

Some technical details: For sake of getting across the idea, we neglect the role that probability plays in the actual experiment. If John and I were to exploit entanglement for real, we’d create a pair of entangled photons, he’d take one and I the other, and each of us would send his photon through a polarizing filter and see whether it emerges on the other side. The choice of “left” or “right” card in the video would correspond to the orientation of the polarizer. For John, “left” would be 0 degrees; “right,” 45 degrees. For me, “left” would be 22.5 degrees; “right,” –22.5 degrees. Assuming no experimental imperfections, the probability that we’d both see the same outcome would be about 85 percent for all possible permutations of orientations, except when both of us select “right,” in which case it would be about 15 percent. Cheaters trying to mimic entanglement could manage 75 percent at best.

I hasten to mention that some physicists and philosophers of physics doubt whether spooky action really occurs—to them, particles are no more psychic than humans are. But even in that case, something else equally weird must be going on to give the illusion of spooky action, such as a profusion of parallel universes, messages reaching us from the future, or a radically holistic view of reality. There’s no way to avoid the weirdness altogether. Researchers also debate whether entanglement conflicts—in spirit if not in letter—with Einstein’s special theory of relativity, as David Albert and Rivka Galchen discussed in our March 2009 cover story.

Leaving aside what the entanglement means, so much remains to be learned about the phenomenon itself. A big question is why, even though entanglement is pervasive, we don’t notice it in our everyday lives. Quantum physicist Dagomir Kaszlikowski recently offered a new approach to solving this problem. The answer, ironically, may be that the very pervasiveness of entanglement camouflages it.

To help explain further what entanglement means, we’ve also asked quantum physicist Vlatko Vedral and physicist-historian David Kaiser to describe the long and winding road that quantum entanglement took to becoming accepted. In a sense, entanglement is so weird that we hope our video will not demystify it, but mystify it.

George Musser About the Author: is a contributing editor at Scientific American. He focuses on space science and fundamental physics, ranging from particles to planets to parallel universes. He is the author of The Complete Idiot's Guide to String Theory. Musser has won numerous awards in his career, including the 2011 American Institute of Physics's Science Writing Award. Follow on Twitter @gmusser.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Zou Sir 10:54 pm 01/30/2012

    It is a good way to demonstrate deep physics by everyday life experience, but quantum entanglement is not proper for this, because entanglement can hardly appeare in daily life for the fact that the superposed state which is essential for entanglement experiments is very fragile. Also, the correlation in classical world is not the same as that in quantum world, this should be emphasized.

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  2. 2. hybrid 3:40 pm 02/3/2012

    The only solution which avoids being real spooky is to a have a less spooky one. Of course I mean the elephant in the room —- dynamic space, otherwise known as the ether. The “Dynamic Ether” posits that all matter is formed and maintained by a stream of energy otherwise known as gravity. This may not explain entanglement but it does provide a medium through which the entanglee’s could communicate.

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  3. 3. billsincl 4:29 pm 02/3/2012

    The problem is – that it cannot be used to communicate information faster than light.

    The reason is: You BREAK the entanglement as soon as you observe one of the particles. For example if you deflect one with a mitror, the other one will NOT be deflected.

    For example, if I observe one of them, I can say what the other was doing UP UNTIL I observe it. But I cannot remotely change the behavior of the other one.

    Modern technology does not allow us to observe the state of a particle without modifying it in some way. You have to deflect it somehow, or absorb it into a sensor. So the entanglement is always broken.

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  4. 4. Thim 6:43 pm 02/3/2012

    Nothing is spooky about entanglement. In classical mechanics this is a normal phenomenon: like the camshaft in a car engine is doing the same: Instantaneous synchronisation of distant valves. Old stuff. Engineer are laughing, me too.

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  5. 5. debu 9:59 pm 02/3/2012

    The problem is you cannot observe both the effects at both places at the same time. This is how we get confused. Read balloon inside balloon theory.

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  6. 6. RussOtter 12:48 pm 02/5/2012

    Try this piece of the π.

    The ether is local and non-local at all times. Similar to the phenomena of “Superposition’s”, where objects are in two places at the same time.

    Entanglement leverages or acts upon this ether’s additional phenomenon. That is why from a finite world it is hard to detect, much like dark matter or dark energy. It is of a dimensional quality that defies conventional mathematics, yet is the underbelly of our very existence.

    Additionally, since space and time are digitized, by my own assumptions, and logical notions of a finite world, which is certainly built by Planck blocks. I simply deduce that waves, may suspend space and time and connect all things at one time, yet still allow for infinities to separate particle[s], if you will.

    This is all food for thought: So Cheers to all in this pursuit of knowledge!

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  7. 7. jgrosay 4:22 pm 02/5/2012

    Oh what a pity, if it’s all a lie !: prove to me that you’re divine, change my water into wine…
    Cute leggy girl. XXOO

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  8. 8. kenlbear 7:26 pm 02/7/2012

    Everything in the universe was entangled in the initial monobloc. Now, after several symmetries are broken, entanglement is so weak it is visible only in very protected conditions.
    Could it be that absolute determinism was also broken at the same point?

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  9. 9. gesimsek 5:30 pm 12/19/2012

    Is it possible to explain entanglement of electrons with referance to the behaviour of photons? As we all know photons, like other electromagnetic forces, can act like a particle and a wave. So, what we call entanglement is the behaviour of electrons in their wave form, ie, being in more than one place at the same time. Like the ripples on a lake’s surface starting from one single point, the energy of the point is felt all across the surface.

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  10. 10. Caped_Crusader 5:55 am 12/24/2012

    A very entertaining and educative clip.

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