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posted by janrinok on Thursday August 06 2015, @01:11AM   Printer-friendly
from the for-certain-values-of-massive dept.

Roman Schnabel, a physics professor at the Max Planck Institute for Gravitational Physics has published a paper in the journal Physical Review Letters outlining a plan for entangling two "massive" objects. He and his team are still working on a way to actually carry out the plan, but if successful, the group would succeed in entangling two 0.1 kg mass mirrors, which would represent a much larger example of entanglement than anything that has come before—up till now the largest objects to be entangled were of micron size.

Entanglement is of course the odd and perhaps a little eerie situation where two or more objects are connected in a way that cannot yet be explained—measuring one causes the other to be impacted instantaneously. The phenomenon was predicted back in the 1930's by Einstein, Podolsky, and Rosen. Over the years, scientists have developed ways to cause particles and then tiny objects to become entangled, but it still was not clear if a way could be found to cause objects large enough to be governed by classical physics to be entangled. In his paper, Schnabel draws up a means of achieving that goal, and notes that he believes it can be done.

http://phys.org/news/2015-08-physicist-unveils-entangling-massive.html

[Also Covered By]: http://physicsworld.com/cws/article/news/2015/aug/03/plan-for-supersized-entanglement-is-unveiled-by-physicist

[Abstract]: http://journals.aps.org/pra/abstract/10.1103/PhysRevA.92.012126


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  • (Score: 5, Informative) by AnonymousCowardNoMore on Thursday August 06 2015, @04:25AM

    by AnonymousCowardNoMore (5416) on Thursday August 06 2015, @04:25AM (#218948)

    It is impossible to communicate FTL with entanglement. You don't get to control what the entangled particles on either side do, only what you do to them. The combined information of what was done to each particle and how it responded shows a correlation. For example, f I tell you (1) what the particle on the other end did, you can combine that with (2) what the particle on your end did and (3) what you did to the particle when it did so to infer (statistically) (4) what I must have done to the particle when it did (1). Entanglement transfers zero bits of information; although it can help you hide bits sent with the aid of another channel.

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  • (Score: 2) by TheLink on Thursday August 06 2015, @10:06AM

    by TheLink (332) on Thursday August 06 2015, @10:06AM (#219023) Journal

    It is impossible to communicate FTL with entanglement.

    Ah but what if YOU were one of the entangled particles? ;)

  • (Score: 2) by hubie on Thursday August 06 2015, @01:57PM

    by hubie (1068) Subscriber Badge on Thursday August 06 2015, @01:57PM (#219074) Journal

    I really can't figure out why your comment was modded "Flamebait". Physics haters gonna hate, I suppose.

  • (Score: 1) by puzzled_decoy on Thursday August 06 2015, @05:20PM

    by puzzled_decoy (5524) on Thursday August 06 2015, @05:20PM (#219164)

    I don't understand this. If you know the properties of the system as a whole, and you know how a particle on your end behaves, you can determine what was done to the particle to cause that behavior. Why doesn't that count as a transfer of information?

    • (Score: 3, Informative) by AnonymousCowardNoMore on Thursday August 06 2015, @06:56PM

      by AnonymousCowardNoMore (5416) on Thursday August 06 2015, @06:56PM (#219212)

      The particle responds but you don't get to choose how—it's random.

      Let's say we pass each particle through a (plane) polarising filter. We keep th first one fixed for simplicity (it doesn't matter) and can rotate the second filter. First, we send one particle through the filter and it is randomly either absorbed or passes through the filter. It behaves as if its polarisation were chosen uniformly from a full rotation. A particle's probability of passing through a filter, given some known polarisation relative to the filter, is 1 if it is polarised the exact same way as the filter, 0 if at a 90 degree angle to it and in-between if rotated somewhere in-between.

      When the second particle is observed either passing through or being absorbed, it too appears to behave as if the polarisation were chosen uniformly from a full rotation (i.e. no different from a particle which isn't entangled with anything). The trick comes when you compare the information from the two sides. Then, suddenly, it becomes that the behaviour of the second particle is always either exactly the same as that of the first or the exact opposite, with equal probability.

      So if the first particle is absorbed, there is a fifty percent chance that the second particle will be absorbed or pass exactly as would a particle that had been polarised by the filter passed by the first particle. And a fifty percent chance that it would behave like a particle that passed through a filter at a 90 degree angle to that first filter. Similarly, if the first particle is absorbed, there is a fifty percent chance that the second particle will behave in exactly the same way as a particle which had been passed through a filter at a ninety degree angle to the first filter (being then polarised in the same orientation as the absorbed one) and fifty percent of behaving like one that was polarised by passing through the first filter (at a 90 degree angle to the behaviour of the first particle).

      With some further effort it can be shown that it is impossible for the particles to behave in the exact way that they do by following any pre-arranged plan (unless they were in contact and somehow able to make such a plan during the Big Bang).

  • (Score: 2) by captain normal on Friday August 07 2015, @04:14AM

    by captain normal (2205) on Friday August 07 2015, @04:14AM (#219417)

    From your description it seems as though 4 bits were transferred and at the same instant. The only to work on is scale and distance.

    --
    When life isn't going right, go left.
    • (Score: 2, Interesting) by AnonymousCowardNoMore on Friday August 07 2015, @02:25PM

      by AnonymousCowardNoMore (5416) on Friday August 07 2015, @02:25PM (#219579)

      No. I did not specify a binary system of 90 degree rotations only but that is a possibility and let's keep it that way for simplicity. You can use entanglement to read out one bit of information only if you are given a bit of information (on decoding the entanglement-transferred bit) which was transferred by some other means, gaining nothing.

      Let's pretend for simplicity that data transfer via entanglement is lossless (it isn't by any stretch of the imagination). You, on your end, do something and make a measurement (the first two bits you refer to). That has nothing to do with anything I did on the other side and you have no information from me at that point. I can send you a bit of information via some other channel, in which case you get one bit of information. Alternatively I can encode the bit of information in what I do to my side of the entanglement experiment, but you cannot read it. If I can send you one bit of information via the other channel, that allows you to infer something about what I did to my side of the experiment, you can now decode the one bit that I encoded in the entangled system. That bit that I send you is useless for communication because it is chosen randomly by nature, not by me. In other words, no matter what we do, I can send you (at most) as many bits as I send you via a conventional communications channel, and never before those reach you.