Two Diamonds Get Quantum Entangled, Physicists Report

By Veronique Greenwood | December 2, 2011 2:17 pm

Atoms are governed by the strange laws of quantum physics—they can communicate across long distances, teleport, and perform myriad other acts that sound straight out of science fiction. But although we’re made up of atoms, we can’t do any of that stuff. We’re governed by the laws of classical, or Newtonian, physics, where there’s no teleporting allowed.

How many atoms have to get together for classical physics to take over? Many physicists would dearly like to know, and, in an effort to suss out just when the change-over happens, have set up numerous experiments in which they watch for signs of quantum behavior in ever-larger objects, from molecules to nanoscale slivers of metal. But a paper published this week in Science takes the cake. Researchers report that they have observed entanglement in two three-millimeter-wide diamonds.

Entanglement is one of the stranger properties of quantum objects. Entangled items are intimately linked, so that whatever happens to one of them somehow (we don’t know how) affects the other. For a technical explanation of how the experiment worked, check out John Matson’s coverage at Scientific American, but, in essence, the researchers set the diamonds vibrating and then poked them with a laser so they would emit a packet of vibrational energy. They were able to show that the packet did not come from one diamond or the other but from both, a sign that entanglement was at work. And what’s more, the diamonds were at room temperature, a real oddity in a field where most objects have to be supercooled or put in other extreme situations for quantum properties to be observed. Although the entanglement didn’t last long (only 7 picoseconds), the fact that it was in large objects at normal temperatures is pretty cool.


  • Torbjorn Larsson, OM

    “whatever happens to one of them somehow travels (we don’t know how) to affect the other.”

    No, and we do know that there is no causal connection, QFT is compatible with relativity. That is what the Bell test experiments validate to the highest certainty (some 20 sigma!) in physics.

    Entanglement simply means correlated wavefunctions. Here is how it would work classically:

    Let Charlie pick pairs out of a pack of cards, place them in matching colored envelopes and send halves of pairs to Alice and the corresponding halves of pairs to Bob. Then Alice throws a dice, let the number pick a color, opens the envelope and presto! She can magically tell what card Bob will see when he opens the same colored envelope.

    The difference in the quantum case is that it is the environment of the setup that decides how colors are perceived. (Whether to interpret a polarization as orthogonal or parallel.) It can be changed during an ongoing experiment even. But that information that is needed for interpretation, and the result, is transmitted causally.

    Many people have a vested interest in making anything quantum appear magical and woo-ish and/or gods-of-the-gapish. But the physics here is actually simple compared to, say, quantum computing .

  • Iain

    Torbjorn Larsson, OM Says
    a bunch of baloney. he/she doesn’t understand the principal. What was done to one somehow affected the other.
    It wasn’t a mail out, it was the same colored envelope showing up without going through the post or a messenger service.

  • http://DiscoverMagazine Templar 7

    Yeah, I’d like to see it on Video.

  • Bruce

    Good luck getting something that lasts for picoseconds on film.

  • Michelle

    Let’s get this straight…diamonds are not governed by the laws of Quantum Physics. QP describes (rather imperfectly at this point) some of what is going on in the universe There is no “classical” or “quantum” law, there is what we observe and describe via our flawed understanding in one subset or the other. The universe doesn’t care about our labels, it goes by its own set of rules which we are just beginning to learn.

  • Geack


    But we do have two sets of tools for observing the universe, and one works at larger scales while the other works at smaller scales. The point at which one set of tools ceases to be useful and the other becomes useful is currently unknown. That’s what this study is investigating. I’m not clear on the point of your comment.

  • m

    Weird things happen when mass approaches zero. Right now, there are those studying this that think we are seeing that state of matter just before/after it converts to energy (0 mass) and then back to having mass again. Meaning E=mc2 still governs the really small.

    Personally, I’ll leave that to the researches to figure out.

    Like the duality of quantum physics, I can see “both sides”.

    A nice article Discover – thanks.

  • David C. R.

    @ Michelle… If diamonds aren’t governed by the laws of quantum physics explain how two of them were entangled, which is a PURELY quantum process. Further, it’s a bit foolish to assume that just because nobody currently understands how things at the quantum level seemingly change the rules they play by at larger scales that it means they aren’t governed by quantum rules. You can’t build the 10th floor of a skyscraper without first building the 9 floors below it and that 10th floor would, by necessity, obey the same rules as those lower floors. In fact, you have to change how you build all of the preceding floors if you intend to be able to build all the way up to a 10th floor. If you don’t account for the extra size/mass/etc. (including even the conditions that would exist as you reach that higher level, such as increased drag from wind, and vibration from tectonic activities, things that, so far as we know, don’t exist at quantum levels) your building falls apart. The rules don’t change, I would think, they’d just be used differently, and it’s that part that we don’t understand. All science is imperfect because our understanding is imperfect. Science, including quantum physics, could best be defined as ways in which the human race is attempting to perfect it’s knowledge and understanding. And in case you haven’t been paying attention: quantum physics has actually shown that at some level the universe cares very much what we think about it. And if I’m wrong then there are several experiments that have results that can never be explained. And if everything has an explanation then either I can’t be wrong or someone has to explain why this universe reacts to us without using our presence, or the lack of our presence, in it as part of their explanation which can’t be done.

  • Brian Too

    There’s a surefire Nobel to anyone who successfully explains how quantum entanglement works, and why it does not respect c in terms of information transfer.

  • David C. R.

    Because you can’t C it… (I know it was awful but I couldn’t resist.) I’m speculating, admittedly, but my personal thought on the matter is this: do you always obey the same rules as those you set for your child? Light, and therefore the speed of light, can’t exist without quantum particles getting together and creating them, the same as a person’s child and the child’s parents. The rules are made by the parent, and just like a parent if quantum particles choose to disobey their own rules, they can do that. We see a similar pattern in the correlations between things like how atoms and molecules don’t always play by the same rules, nor do molecules and cells, etc. and I don’t see why things at the quantum level should be any different. But again, I’m speculating.

  • Benjamin

    Everybody who is wondering about a few of the properties of quantam mechanics, watch NOVA: Fabric of the cosmos. The third show has everything (almost) about quantam mechanics, and the other shows are cool, too.

  • Jay Fox

    Extra dimensions. String theory calls for them. Maybe they are for real. Maybe, in one of those very small dimensions, the distance from one location to another is so very small that getting from one to another would seem to violate C.

    I would like to see a quantum entanglement experiment performed over a very large distance. Is the entanglement really instantaneous? Any delay, even the tiniest, would hint at an extra-dimensional connection. The distance would have to be huge to show even the smallest delay, since we are investigating a theorized tiny dimension to begin with.

    This might be the kind of experiment that theorists need to discover the properties of these predicted extra dimensions.

  • Lou Jost

    #9, Brian Too, no information travels faster than light in these quantum effects.

  • David C. R.

    Hey Lou, if no information travels faster than light, or otherwise, then can you explain how changing the state of one changes the state of the other with a delay period beyond what currently understood laws of physics can account for? An information exchange of some variety MUST occur, even if we can’t detect what, or how. You can’t just flatly deny a theory and not give your reasoning for it or you just come across as an idiot. I apologize if you find that offensive but it’s the truth. This is (perhaps not officially) a forum for intelligent discussion which, in order to function as such, requires that those with differing and even dissenting opinions, theories, or beliefs, to explain how they have reached their conclusions. I’m not attempting to be rude, or condescending, but I would like to hear your theory, if you have one.


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