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Quantum Theory Experiment Said to Prove "Spooky" Interactions (economist.com)
universe520 writes: Albert Einstein was troubled by how two particles can communicate with each other even if they are on opposite sides of the galaxy. Today researchers in the Netherlands have closed the final two loopholes in how quantum entanglement works. The Times reports: "The new experiment, conducted by a group led by Ronald Hanson, a physicist at the Dutch university’s Kavli Institute of Nanoscience, and joined by scientists from Spain and England, is the strongest evidence yet to support the most fundamental claims of the theory of quantum mechanics about the existence of an odd world formed by a fabric of subatomic particles, where matter does not take form until it is observed and time runs backward as well as forward."
"and time runs backward as well as forward."
It had to be published today, right Doc?
and this is the basis of the flux capacitor and all of time travel. About time it got discovered.
Spooky action at a distance is only spooky if one assumes distance is real and not an emergent property of a projected/holographic universe. In the same way in a computer simulation/game the distance between objects in no way represents the "distance" between them in the computers memory, perhaps our universe works at a similar level of abstraction.
Just press the red button on each and wait for their red LEDs to start blinking to pair the particles.
No, with entanglement it would seem that you cannot force one particle to a state so that the other is switching as well. Thus, you cannot effectively use this as a communication channel.
A very crude picture can be stated as the following : you send two letters containing the same unique number (0...9) to both Alice and Bob (who also know this rule). When Alice opens her letter and reads the number, she knows that Bob has the same number but she cannot use that to communicate a particular number to Bob directly.
WARNING : This explanation is using the hidden variable model which is wrong, as the EPR paradox/Bell's inequality and these researchers are proving. But this is the only simple explanation I know (with my limited knowledge of QM) to convey the fact that entanglement can not be used as a communication channel.
Even if that observer is us, in the future, moving backwards.
The cesspool just got a check and balance.
We all know it had an observer, The Doctor goes back to watch it on a regular basis.
Do not look at laser with remaining good eye.
Knowing how humans work, we will make a UDP broadcast call giving our location with "hello" and a lot of annoying children in different languages saying hello.
This will cause a galactic armada to come here and obliterate us for messing up the last half of the season finale of "glip Glopr the unstoppable".
Do not look at laser with remaining good eye.
I've never actually heard a convincing argument as to why this explanation is wrong. It seems to describe the Bell inequality experiments perfectly.
Last post!
Don't be silly. They're just here to construct a hyperspace bypass, which will require the demolition of the Earth.
Oh, and don't bother complaining. The plans have been on file at the local office in Alpha Centauri, if you wanted to file a complaint, you should have done it then.
I thought all this means is that you can entangle two particles when they are close. Basically this means all you know is one is + and one is -. Then if you separate them and measure one you know what the other one is. That doesn't seem so spooky.
I love Jesus, except for his foreign policy.
Information IS exchanged. Absent a hidden variable that is carried along with both entangled particles, they have to communicate their state when observed. We cannot use that process to communicate arbitrary information of our choosing faster than light.
Quantum Mechanics is a Great Tease.
At first it looks like you can do wonderful things, like send messages faster than light or travel back in time. BUT when you look at the details or actually try it, there's always a catch that limits the usefulness.
Me thinks Quantum Mechanics was designed by Oracle lawyers: it looks like you got a great big powerful database...until you go to use it and find out the contract does something ridiculous like count "transaction" as each table cell read, NOT per query, filling your license quota the first week*.
Reminds me of a joke:
Q: "What's the difference between Larry Ellison and God?"
A: "God doesn't think he's Larry Ellison."
Maybe he does.
* Hypothetical example only based on patterns of more complex actual examples. Don't sue my tail off.
Table-ized A.I.
It's not intractable, but it is a challenge. (Well, not "five"; I kinda hate that expression. But "scientifically interested layman" isn't beyond reach.)
Try it this way: Quantum mechanics rules are the "real" rules of the universe: objects don't have exact positions or locations. Rather, what you get is a wave that describes the object. One way to interpret that wave is that it predicts the probability that it could be at any particular place. The total behavior of the object is the sum of those probabilities. It really is in every single place, all at once, though "more" some places than others. These waves can even cancel out. That's very much at odds with what we expect.
Here's the thing with probabilities: the more of them you add up, the more they behave like the average. That is, there's a lot of uncertainty in the roll of a 20 sided die. But you know that if you roll it a thousand times, the average is going to be very close to 10.5.
Real-world objects contain far, far, far more than a thousand objects. If you work the sum of the quantum waves for that many objects, what pops out is remarkably like plain classical physics. So, everything you see looks like ordinary physics.
But if you design your experiment carefully, you can make some of the quantummy behavior show up. The most classic one is the two-slit experiment: you restrict the particle's path to one of two places, and you get interference waves. But if you modify the experiment so that it is interacting with large-scale objects like a detector somewhere in the process, the waves vanish. (A detector is something that has large-scale changes between the particle's presence and the particle's absence.) The confusing part is that you can put the detector in places where you wouldn't expect it to have an effect, but since the particle is "everywhere", it affects it in counterintuitive waves.
Proving that for certain turns out to be tricky. The difference between "the particle really is (partly) everywhere at once" and "the particle is actually in only one place, but you can't tell" is pretty subtle. You can show it by carefully counting up "entangled particles", where the two probability waves are linked. It would be natural to think that particles were exchanging information to maintain the linkage, faster than the speed of light, but the quantum rules actually rule that out. Proving it for certain is hard, since you're talking about very tiny things and very fast speeds. We actually have been doing it for decades, but since it's so hard, there were usually loopholes. This experiment finally nails the last of them shut.
The solution to the chicken-egg problem lies in the behavior of the sums: big objects behave like you expect them to because the probability of them not doing so becomes vanishingly small. There's still some fiddly bits: that "vanishingly small" isn't quite zero and nobody exactly knows where it goes. Some say "another universe"; others (like me) just put our fingers in our ears and say "I don't know but shut up and calculate la la la".
Did you read the article? It gives a pretty good description of the experiment.
They create two electrons, A and B, completely independently, in two different, widely separated labs. They use those electrons to produce a photon each (Ap and Bp), and send those photons to a third lab. The properties of the photons will depend on the properties of the electrons, but the electrons were created independently so the properties of the photons should not be correlated with each other. In fact, if at this stage you test the electrons and photons, you find that A and B and Ap and Bp are not correlated.
That third lab entangles the photons. Then the two original labs test their electrons. Now they discover that the properties of A and B ARE correlated.
Don't we have an intractable Chicken-and-Egg problem here?
The difficulty in understanding is mostly in how the experiment is described. This is the latest in a series of increasingly technical experiments exploring pretty odd corner cases in quantum theory. They're important because they close the last loopholes, the last excuses that anyone who really understands the field had in believing in any sort of classical underlying reality.
There's no time travel here. There's no FTL communication here. Either of those would actually invalidate the experiment. The point of this all is: you simply can't explain these results classically. And that's nothing new - there's a long list of such results.
Here's any easier experiment to understand. Take 2 polarized filters, and measure the amount of light that gets through as a function of the angle between them. With a classical model of polarization, you'd expect it to fall directly with the angle, but instead it falls of as cos^2 of the angle. Most of these Bell Inequality experiments are very similar in principle, they just use 2 entangled photons or electrons instead of one beam of light passing through two filters in series.
The part about "hidden variables" vs "spooky action at a distance" is only relevant if you're trying to explain the result classically. If you give up notions of a classical underpinning to physics, if you accept that e.g. the spin polarization of an electron simply isn't about the axis of a spinning ball (a ball with a bar magnet inside), then there's nothing surprising here. Sure, it's weird, but it's weird in the exact same mathematical way as the beam of light passing through 2 polarizing filters.
This all just shows that the idea of an electron or photon as any sort of particle, like a dust mote only smaller, is simply a flawed metaphor that you can't reason from. But since there was no reason to expect them to be that way, it's not even that weird.
(What's really weird, though, is that of you take 2 polarizing filters at right angles, such that no light gets through, then stick a third between them at a 45 degree angle, then it's as bright as one filter alone.)
Socialism: a lie told by totalitarians and believed by fools.
No. You're taking "observation" too literally. A better explanation is -- nothing exists in any definable state until it interacts with something else.
That's what "measurement," "observation," and "detection" generally mean -- some sensor capable of being triggered by an event was triggered... something in a quantum state interacted with something else and the wave function collapsed.
No conscious observer is required. Just stuff interacting with stuff.
This is easier for me to grasp in the many-worlds interpretation of quantum mechanics. There is a universe in which Alice is holding "0" and Bob is holding "1", and another universe in which Alice is holding "1" and Bob is holding "0". Those two universes separate the moment Alice (for example) looks at her bit. At that point she is certain that Bob got the opposite bit.
Take 2 polarized filters, and measure the amount of light that gets through as a function of the angle between them. With a classical model of polarization, you'd expect it to fall directly with the angle, but instead it falls of as cos^2 of the angle.
The classical E.M. theory perfectly predicts the cos^2 term. See Malus law.
What's really weird, though, is that of you take 2 polarizing filters at right angles, such that no light gets through, then stick a third between them at a 45 degree angle, then it's as bright as one filter alone.
No, you would have less power than a single polarizer. This also very well explained by Jones calculus.
Quantum mechanics rules are the "real" rules of the universe:
No - in fact, we know that QM is imperfect; being a scientific model implies that much. It is in many ways the fundamental axiom of science, that we can not prove truth through observation, we can only disprove false predictions. Don't get me wrong - QM is a marvelously robust theory, but unfortunately, so is GR, and the incompatibility between them is a very strong indicator that there is a lot of reality that is not covered by either theory, and that we probably have to find a starting point that is alien to both theories, to unify them.
One of the strengths of GR is its logical simplicity; QM lacks that in so many places. There are too many wooly constructs that lead people's thinking astray, like the idea that it is somehow fundamentally impossible to know details below a certain limit (Heisenberg) or that things only exist if we observe them - or that "everything is probabilistic in nature". The truth of the matter is, I bet, that these things are artifacts of the available methods. When you rely overwhelmingly on statistical methods for analysing your observations, then of course you end up thinking in terms of probability, which s no more than 'predictive statistics', in many ways. And when you observe by throwing wave-forms at each other to see how they interact, then of course there will be limitations to how well determined your observations will be - it is hard to observe detail finer than the wavelength, for one thing. And the idea, that things only exist when somebody observes them is a wild overinterpretation of both theory and observations.
We really, really need to clear our minds of this sort of quasi-religious thinking, because the unhappy thing is that it stops us from even looking outside the box.
It would be nice if the term "observation" was clarified in every explanation of the double slit experiment. I'm sick of every explanation including the phrase, "as if it knows it's being watched", trying to make real science feel more like magic, rather than the other way around.