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