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Einstein's 'Spooky Action' Has Been Demonstrated On a Massive Scale For the First Time (sciencealert.com)
schwit1 shares a report from ScienceAlert: For the first time, scientists have managed to show quantum entanglement -- which Einstein famously described as "spooky action at a distance" -- happening between macroscopic objects, a major step forward in our understanding of quantum physics. Quantum entanglement links particles in a way that they instantly affect each other, even over vast distances. On the surface, this powerful bond defies classical physics and, generally, our understanding of reality, which is why Einstein found it so spooky. But the phenomenon has since become a cornerstone of modern technology. Still, up until now quantum entanglement has only been demonstrated to work at the smallest of scales, in systems based on light and atoms, for example. Any attempt to increase the sizes has caused problems with stability, with the slightest of environmental disturbances breaking the connection. But new research changes all of this, by demonstrating that this "spooky action" can indeed be a reality between massive objects. We're not talking massive in the black hole sense but in the macroscopic sense -- two 15-micrometer-wide vibrating drum heads. And the next step will be to test whether those vibrations are being teleported between the two objects. The research has been published in the journal Nature.
Entanglement is a cornerstone of modern technology? Say what?
I think that's something like 60 times larger than modern transistor architecture.
Given we're used to entanglement involving single atoms, it is astonishing in size.
Changing the spin of A breaks its entanglement with B.
Based on current knowledge, you cannot transmit information using entanglement.
Convert it into Planck lengths and you'll see.
In most ways it's not different. All these "entanglements" are just the basic laws of physics in action. So for example spin is conserved, so if two photons are created and speed away in opposite directions the laws of physics their spins must add up to 0. Therefore you measure the spin of one as 1, the spin of the other must be -1.
The issue as the physicists see it is a quantum variable is doesn't exist until it's measured, where "doesn't exist" means can have no effect on the universe. Although instead of "doesn't exist or has no value" they like to say it is a superposition of all possible values. Another way of saying the same thing is the particle has no idea what it's quantum values are because if it did it would behave differently. The classic example is the double slit experiment, where a photon very confused about where it is and forms an interference pattern. But if you measure where it is before it gets to the slits so it (and you) know the values of quantum variables, the pattern disappears.
The point is, before you measured it the spin on your photon didn't have a value. And that's true for it's entanglements partner too. Then you measure it and now you know. But it's entangled particular also knows its spin at the same instant, and starts behaving like it does. (Because if it didn't the laws of the universe would break down, eg charge or momentum wouldn't be conserved.) But if it's outside the light cone how could it know what the value it must take on to so the laws of universe aren't broken? It can't, so it must be spooky action at a distance.
The term "local hidden variable" is an explanation for how this happened. It means the photon knew all along what's spin was, but it was cleverly hiding it in this hidden variable. The key point here is it's value was computed at the moment of entanglement. It was hidden from then on until you measure it, but the value was agreed upon when the particles were entangled, and entanglement always happens when they are together, communicating. Global hidden variable is another explanation - it means the whole universe knew, which when you think about is means there is communication fast than light, because otherwise how could it be "global"?.
The local hidden variable sounds like the simplest explanation. The original reason said they said is doesn't work is Bells inequality. It may be still only be Bells inequality - I don't know if anybody has actually seen the double slit effect disappear for an entangled photon when it's mate is measured. I hope there is something more convincing now, because Bells inequality is a subtle argument.
It arises because quantum values are distinctly weird. Take spin for example. In the classic worked, you can look at something spinning and see what axis it is spinning around. In quantum world you can't do that. All you can do is point a ruler in a direction, compare the axis the photon spinning around to the direction this ruler is pointing. (You have to adopt an convention that describes the direction of spin - say ruler pointing up means spinning clockwise, down means counter clockwise on the same axis.) Worse when you point the ruler and ask the question, you force the photons spin to align with the ruler - so the measurement changes the thing being measured. But you do get something out of it - you are told whether the spin now (after it was changed by you observing it) agrees with the direction your ruler is pointing (up or down). So you get a single boolean answer, and that's all you get. But your measure is real and repeatable in the sense that if you do it again with the ruler aligned in the same way, you will get the same answer every time (because remember the spin is now aligned with your ruler). And if you measure it a again with the ruler pointed in the opposite direction (eg up instead of down), you will get the reverse answer every time. This sounds intuitively correct, and it's also somewhat intuitive that if you ruler isn't parallel it isn't entirely obvious