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Quantum Entanglement of Macroscopic Diamonds 160

Posted by Soulskill
from the simultaneously-a-girl's-best-friend-and-not dept.
New submitter ananyo writes "A pair of diamond crystals has been linked by quantum entanglement — one of the first times that objects visible to the naked eye have been placed in a connected quantum state. 'This means that a vibration in the crystals could not be meaningfully assigned to one or other of them: both crystals were simultaneously vibrating and not vibrating (abstract). Quantum entanglement — interdependence of quantum states between particles not in physical contact — has been well established between quantum particles such as atoms at ultra-cold temperatures. But like most quantum effects, it doesn't tend to survive either at room temperature or in objects large enough to see with the naked eye.'"
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Quantum Entanglement of Macroscopic Diamonds

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  • by LateArthurDent (1403947) on Friday December 02, 2011 @05:23PM (#38243472)

    As near as I can understand this they're entangled so that vibrations in one are indistinguishable from vibrations in another, they both do the same thing at the same time (or near it at least)... doesn't this imply the ability to entangle two whatevers and transit information via entanglement induced vibrations?

    No, they are in opposite states. If you measure one of them, you'll determine that it is either vibrating or not. If it is vibrating, the other diamond is not, if it's not vibrating, the other diamond is vibrating. Before the measurement, they're entangled, so they are considered to be both vibrating and not vibrating simultaneously.

    That said, I don't know much about quantum effects, so I can't read the paper and understand it, but the description in the article made it seem like what's actually happening is just that the experiment is set up such that only one diamond can be vibrating, but you don't know which one it's going to be. So at all times, one of the diamonds is vibrating, the other is not, and you only know which is which when you measure one of them. Which doesn't sound like anything special. It's like me getting two playing cards, an Ace and a King, and putting them in a table face down. Then I ask you, "which one is the card in the left?" and you answer, "it's both a King and Ace. Until I flip it over, and then I can tell you what the other one is." Which is ridiculous, the card is one card specifically, you just don't know which one it is. So I suspect the media writeup screwed up, although it still seems way better than most, since they didn't mention stuff like ftl communications which pops up in almost every entanglement story even though we all know entanglement can't enable ftl communication.

  • by Anonymous Coward on Friday December 02, 2011 @07:14PM (#38245186)

    Well, as others point out I oversimplified things a bit. Quantum physics states that, in a sense, both and neither are vibrating so long as they are entangled, and only one actually vibrates once observed. However I believe that many view that as merely a mathematical system for approximating what is really going on (don't take my word for this, as I am by no means sure about this point), but that goes well past my knowledge. In your example, there is an objective reality about which box the ball is in. It may or may not (and experiments indicate not) be true that there is an objective reality about which diamond is vibrating prior to the observation.

    But how can you prove that both diamonds were in a simultaneous state until observed? It seems just as likely that the photon went one way or the other and your just now finding out which way it went when you observed it.

    Just like the two boxes, one has a ball and one doesn't. Just cause you don't know which one has the ball, doesn't mean it simultaneously exists and doesn't exist.

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