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"Spooky" Science Points Towards Quantum Computing
Stony Stevenson writes to tell us that University of Michigan physicists have been able to establish an "entanglement" between two atoms trapped more than a meter apart in different enclosures using light. This shows how two different atoms can have a sort of communication, something Einstein referred to as 'spooky action-at-a-distance'. "By manipulating the photons emitted from each of the two atoms and guiding them to interact along a fibre-optic thread, the researchers were able to detect the resulting photon clicks and entangle the atoms. Professor Monroe explained that the fibre-optic thread was necessary to establish entanglement of the atoms. But the fibre could be severed and the two atoms would remain entangled, even if one were 'carefully taken to Jupiter'."
> a small machine that measures that's designed to react when it an electron comes "de-entangled" That's your mistake. There's no possible way to detect that an electron has suddenly become "de-entangled".
The only thing the machine can measure is the electron's spin in either of two axis. Now, say you measure it in the left-right axis and its spin comes up as left. What do you know now? You do know that if the corresponding entangled particle has been measured in the left-right axis, it would have come up as right. But this does not tell you whether it has actually been measured. There is no way to tell whether the other party has measured their particle. No information has been transferred. You can't violate causality, even with quantum entanglement.
What's purple and commutes? An Abelian grape.
No. You can't transfer information across an entanglement. Faster than light communication is as impossible as it ever was; and causality has not yet been knowingly violated.
What's purple and commutes? An Abelian grape.
Ok, your comment is badly mangled, but I think I get the gist of it and I'll try to explain.
The problem is that we can't currently control what state the two disentangle into, we can merely guarantee that they share a state in common. Special relativity doesn't explicitly deny something happening faster than the speed of light, just data being transmitted faster than that limit. Because we can't determine anything from the two entangled electrons other than they share a common state, we can't actually get any data out of the system, thus there is no discrepancy. There's also the fact that determining if they are entangled is itself a measurement and thus the act of checking for entanglement breaks the entanglement. We can only verify they are entangled by checking after the fact that they both have the same state when we measure them, otherwise there is no way to know if they are entangled or not.
Curiosity was framed, Ignorance killed the cat.
It's more like you have a bag of blue and red billiard balls, you pull out two randomly without looking at either ball's color, place each in a box and ship them halfway across the world. The two boxes are opened up and observed, and each time one box contains a red ball the other box will always contain a blue ball.
What's even weirder is that in the quantum mechanical world, it's not that your picking two particles that are either in one state or the other with equal probability and it turns out that you always pick up opposite states. Rather it's that you have two particles that are both in both possible states at the same time. When you measure the particle it collapses into one of the two known states, but up until then it is in a superposition of both. And when you do that to one of the two entangled particles, the other particle will also collapse into one of the two states at the exact same time and you will know exactly which one the other particle will be in based on what state your own particle is in.
The laws of probability forbid it!