Quantum Theory Experiment Said to Prove "Spooky" Interactions (economist.com) 257
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." (Score:5, Funny)
"and time runs backward as well as forward."
It had to be published today, right Doc?
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Nah, it's ten days early.
Re:"and time runs backward as well as forward." (Score:5, Funny)
Remember that these are the same people arguing against the Universe having a creator....
Nah; they've just found that the "creator" worked at what we consider the (heat) death of the universe, and the creation has run backward since then. We don't remember something until the universe reaches the event we're trying to remember, and then it sends a description of the event forward along your time line. This transmission has a significant error rate, of course.
Does that clear it all up? If not, wait a bit, and someone farther back will send a more detailed explanation. Of course, since it'll be traveling longer, there'll be more dropped bits, so we may not be able to make as much sense of it.
Re:"and time runs backward as well as forward." (Score:5, Insightful)
No. They aren't "arguing against" the Universe having a creator. They simply have no evidence FOR one, so they dismiss the idea.
If you have scientific evidence, then please present it. If not, then it's not science and science has nothing to say about it.
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Flux capacitor! (Score:5, Funny)
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Someone needs to tell Stanford to stop making donuts.
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Well, you suck at it. Even as we speak I am gleafully anticipating the time when I will have looked back upon the future with a special gleam in my eye, knowing that some AC on Slashdot couldn't have burst my bubble, even back when I would soon be vulnerable to such slights such as he would soon be trying.
I've been waiting for this! (Score:2)
Re:I've been waiting for this! (Score:5, Funny)
Just press the red button on each and wait for their red LEDs to start blinking to pair the particles.
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Why? Who you gonna call?
Re: I've been waiting for this! (Score:2)
Ghostbusters!
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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 dir
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I've never actually heard a convincing argument as to why this explanation is wrong. It seems to describe the Bell inequality experiments perfectly.
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I've read a number of accounts of the Bell Inequality experiments, and I still don't see how it doesn't boil down to "Alice got X there for Bob got Y", or at least "Alice got X, therefore Bob has a Z% chance of having Y".
The numbers definitely jive with what you'd expect from wave-like phenomena, not particles. But I've never seen any good reason to believe that observation plays a causal part in the system. It's more like observing things locally can tell us what happened remotely - but that's just norma
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This is easier for me to grasp in the many-worlds interpretation [wikipedia.org] 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.
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Not that we know of. If you measure your particle, you know the fellow on the other end will read the opposite measurement. It's like having random number generators at each end that are perfectly synchronized, but always produce inverse results.
You can use it for unbreakable encryption though, by treating your random numbers as a symmetric key with unlimited length. The person at the other end can deduce your key from his own measurements, without ever having to send the key over the channel.
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Sounds pretty useful for cryptography to me (Score:2)
Since you could have a pair of random and shifting strings that nonetheless stayed in sync with eachother, well, that seems like with a bit of effort it could be pretty damn great for certain cryptographic uses.
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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".
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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.
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Said armada will, due to a scaling error, be promptly eaten by a small dog.
No (Score:2)
Nope. See no communication theorem. Basically you cannot communicate *any* information whatsoever.
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Actually it has been proven that no signal can be passed between the two events, even though they seem to be linked.
So no communication or data.
Intelligent Teasing (Score:3, Insightful)
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
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Does this mean faster than light communication is actually possible?
Short answer: no.
Longer answer: entangled particles can only be observed to be in a state, they can't be placed in a state.
The coin analogy is a good one. Imagine that you and a friend a long distance away have two "magic" coins that are guaranteed to show opposite sides: one comes up heads, and you know the other comes up tails, and vice-versa. You can flip your coin, see it come up heads, and you know instantly that your friend sees tails. But here's the catch: you can't control which face shows up. You c
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Hold on though. If I don't actually look at my coin (leave it spinning). Isn't my friend's coin still spinning? Can't we tell that statistically?
Let's say we're firing off entangled electrons. We have a splitter based on the spin of the electron. We redirect the split electron beam at the same target. If our friend is *not* measuring spin with his entangled stream, won't our beam interfere with itself? Won't that interference go away if our friend starts to measure?
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Bell's Theorem. [xkcd.com]
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xkcd just covered this a few days ago: https://xkcd.com/1591/ [xkcd.com]
Distance? (Score:5, Interesting)
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.
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Yes, but why do you think a "real" universe wouldn't be quantized? Having only seen one universe, our own, what evidence do we have of this scenario being somehow not basic?
The fact that it resembles what we do in computer simulations does not imply anything about the reality of the universe. It may be the other way around: simulations work the way they do because the real universe is naturally quantized.
It is an interesting and possibly even correct assertion that someone is running us as a simulation.
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Sure, first they say Pluto is not a planet and next they're going to say it's not the universe. I see where this is going...
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Except there are observations supporting what we'd expect to see if it were a simulation. Kinda. It's highly speculative and involves string theory, but still.
https://www.youtube.com/watch?... [youtube.com]
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When I was young, and thought I was wise, I had a saying that I'd write all over the place - I'd stated it while tripping sack and it kind of stuck. Anyhow, I said, "Time is nothing but man's measurement for the passage of reality." I might have been right.
Re:Distance? (Score:5, Interesting)
I've always assumed that the "distance" was merely due to our observations in three-dimensional space, but quantum entangled particles are "touching" at some higher level dimension. It's a guess.
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Entanglement IS communication, in the proper sense of the word. You cannot use it to send a message, but entanglement without hidden variables implies that information is exchanged between particles.
The holographic universe hypothesis is so named because of it's relation to the principle of holography. Also, your assertion that "real holograms occupy three dimensions" is incorrect. A hologram encodes two dimensional interference patterns, which can be used to create a 3D (appearing) image when properly l
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Entanglement IS communication, in the proper sense of the word. You cannot use it to send a message, but entanglement without hidden variables implies that information is exchanged between particles.
Only if you assume that particles actually exist in the first place, and that wavefunction collapse is objectively real. Neither of those assumptions is particularly well-founded.
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That's true. If the universe is a figment of my imagination, which is likely, then the particles do not need to communicate because their existence could not be other than I imagine it.
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Well, what I really meant was that our best current theory is a quantized field, so individual particles don't really have an independent objective existence but are just a subjective interpretation of certain kinds of vibrations. But your way works too. (At the end of the day it all boils down to how you choose to define words like "information" and "communication" so it's a bit of a tree-falling-in-a-forest thing.)
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The idea of the (reasonable) simulation argument is that not everything would be calculated out to the particle level all the time - the simulator would only figure that stuff out if there was some reason to. I mean, you can simulate the observable, macro-scale behavior of the sun without actually figuring out the position of every quark inside it.
But sometimes, like if some scientist is looking very close, you really do have to figure out exactly where every particle is in order to render that scientist's
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Speaking about the simulation theory, if someone DID design this simulation, then they didn't really bother covering it up. Since the dual slit experiment shows it and it's, well, relatively simple to do.
Unlike the Matrix, no one bothered pulling wool over our eyes it seems.
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I mean, you can simulate the observable, macro-scale behavior of the sun without actually figuring out the position of every quark inside it.
So right now, "up there," there's a conversation going something along these lines...
"Dammit, my universe is running slow."
"Lemme look. Ah, there's your problem - it's the Dutch, poking particles again."
We're lucky we don't get rebooted when we fire up the LHC.
Or maybe we do...
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The "simulated universe" "theory" is a joke. Real computers occupy 3 dimensions
At least, simulated real computers occupy 3 simulated dimensions.
Faster than Light Travel (Score:2)
You just need someone to see you are there, and poof, you are there. No travel needed at all.
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You're just a figment of my imagination and my psychiatrist (also a figment of my imagination) was right.
Classics IV (Score:2)
Physicists correct me if I'm wrong. (Score:5, Interesting)
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.
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You've essentially described a hidden variable theory (the particle is + or -, you just can't see it). This guy named Bell proved that if that's the way the universe actually works then it implies some even spookier things.
https://en.wikipedia.org/wiki/... [wikipedia.org]
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How is that a hidden variable theory?
Its much the same as taking two balls of silly putty and pressing them against opposite sides of a coin. In a dark room. Then taking one of them down the road to your mates place, where he can look at it and know what the one you left at home looks like. Whats hidden? Its only the imaginary "I don't know" probability wave which you "collapse" by looking at one of them. All the rest is just a big mind-fuck. And Einstein was more concerned with the stupid theories pe
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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.
That's only the "non-QM" entanglement. The spooky part of the problem occurs when the particles are entangled in a superposition of states.
The difficulty is that it's hard to describe a non-QM analogy of an object in superposition of states (e.g., cat-is-half-dead). The so called QM bomb tester [wikipedia.org] thought experiment is perhaps one of the easier way to understand how QM superposition might be different that simply an emergent property of an unknown or hidden underlying probability distribution function. Give
Observers irrelevant, no wave function collapse (Score:2)
Wave functions don't collapse. They just evolve with time. A state of superposition is equivalent to oscillating between states in a reversible way. Some interactions lead to state changes that are functionally irreversible because changing back to an earlier state becomes exceedingly impossible. For instance emitting a real photon.
As for observers this is just an interaction like any other. The observing particle becomes entangled with and interacts irreversibly with the observed. There is nothing sp
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This is not a chicken/egg problem. This is now a known scientific fact. The Beginning of the universe, according to this information, must have had an observer.
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aw fuck dude, i should not have just watched back to the future 2 and smoked a bunch of weed before reading that.
We see the past, so its there. I think so I am, makes it so. Life and the universe is an invented illusion, and that is reality. I cant say i know enough quantum mechanics to all but interpret wildly on what you said though.
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http://www.gifbin.com/982288 [gifbin.com]
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We all know it had an observer, The Doctor goes back to watch it on a regular basis.
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Yes but he always skips out the ending as it is to depressing.
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For once, my signature is applicable. Don't worry, I changed it tomorrow to be this today. (I'll take the sleek black spaceship, thanks. It looks more interesting and the result is highly improbable.)
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This is not a chicken/egg problem. This is now a known scientific fact. The Beginning of the universe, according to this information, must have had an observer.
"You're very clever, young man, very clever- but it's turtles all the way down!"
Re:Explain to me like I'm 5 (Score:5, Informative)
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.
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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.
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What's an observer?
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But nothing says if that observer was a chicken or an egg.
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I understand that we don't need to observe it but that it can change behaviors based on the state of observation at the time - like the photons through the slits that misbehave when you leave the room.
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Explain to me like I'm 5
If you insist. [xkcd.com]
Re:Explain to me like I'm 5 (Score:5, Informative)
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".
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Thanks !
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Go watch Brian Cox. Do it right now. Do not delay. There are many choices. Start with The Wonders of the Universe. Get the book. He's got an excellent way of describing things. He does one at the Royal Academy of Science (I think it was their traditional Christmas thingie) that is *very* good. Just go watch him. Seriously. All I watch, for the most part, is documentaries - they're entertainment and not educational for me. He is, by far, one of the best - if not the best. He's like Attenborough for Physics,
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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
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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 p
Re:Explain to me like I'm 5 (Score:5, Informative)
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 [wikipedia.org].
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.
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Classical EM theory predicted no such thing. It was measured as such, and incorporated in theory, without any real explanation from first principles as to why. And it wasn't obvious that electron spin polarization would work the same way.
If you start reasoning about elections as spinning bar magnets that precess along the axis of measurement, then think about measuring them at one angle and the change you'd get the same result when measured at another, you're lead to the wrong answer. Electron "spin" is
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More news (Score:2)
This just in: Schrödinger's cat found dead!
Onlooker confirms cat actually alive!
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https://www.youtube.com/watch?... [youtube.com]
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It's because they're stupid, that's why. That's why everybody does everything.
-Homer Simpson
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but if time can be observed moving both forward and backward, what is the per seconds part of the speed of light value? time has been shown to not be static in this observation, so 1 second could be observed in 100 seconds or .001 seconds... so what is the observed time dimension for the speed of light?
The problem with your question is that you are assuming that time is the same in frames of reference that are moving relative to each other. The short answer is they are not. Take this example from special relativity...
You are in a car driving to run-over an enemy watched by your friend on a nearby grassy knoll. You turn on your headlights and light from your headlights goes forward "at the speed of light" to illuminate your enemy and see his eyes illuminated as you race forward at 100km/h. Your friend
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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.
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It's like rain - on your wedding day!
Isn't it ionic, don't you think?
Or, in other words... (Score:2)
And that's it. I haven't encountered anything that says "Change P1 and P2 changes too" except in speculation and headlines.
Yup. Indeed. Quantum entanglement CANNOT be used for faster-than-life communication.
If my description above is right, then it's "split a pea in two, and if you measure the first half, you'll know that the other half will be a hemisphere with opposite orientation" which isn't too useful.
(with the subtle difference that the real quantum pea isn't actually split in advance. You end-up with a have only the moment you look at it, until that moment both half of the quantum pea exists with 0.5 distribution at both P1 and P2 places)
But basically yes "you'll know that the other half will be a hemisphere with opposite orientation" is a decent simplified explanation of why you can't use it directly for faster-than-li
Re:Change it twice (Score:5, Informative)
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.
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If I'm reading the paper correctly, that's because the results of each experimental run are discarded unless the measurements of Ap and Bp show that A and B are correctly lined up with one another. (Or the experiment isn't performed until the measurements show that A and B are correctly lined up with one another, it isn't entirely clear.)
The Economist article, unsurprisingly, kind of skimmed over that part. :-)
To extend the pea analogy, Alice and Bob both have a half-pea, oriented at random. They both tel
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It's a much more complicated theory, with no obvious advantages, so Occam's razor suggests that we shouldn't get too excited about it.
Also, you can't posit that the pilot wave propagates at the speed of light, because it doesn't propagate through space at all. As per the article: "In de Broglie–Bohm theory, the velocities of the particles are given by the wavefunction, which exists in a 3N-dimensional configuration space, where N corresponds to the number of particles in the system."
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In short, it is because the nature of spin itself is non-classical. Whenever you look at the electrons, they are always either pointing either up or down - never left or right, because there isn't any such thing.
The way in which the is-it-up-or-is-it-down property transforms as you look at the electron from different angles makes it impossible for the spin to be predetermined for more than one angle at a time. If measuring it at one angle would definitely produce a spin-up result, the result of measuring
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This does not permit actual communication. Communication would require that information be transmitted from one end to the other.
Knowing that the state that you observe is also appearing inverted on another particle somewhere else doesn't help you because the state of the particle is random until you observe it. Therefore, while both sides understand that they are viewing the inverse of the other particle,
1. Since, the value observed is random you can't choose what it will be ahead of time. That prevents
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Because the science might be right but the engineering is still extremely far away.
We might be able to entangle two particles in an lab experiment and test them at distance, doing so as a matter of routine with enough particles to form a reliable communication channel across millions of km's with inch-wide precision with something that you can put into a craft? That's still just science fiction. And any mission you launch will still take years to bring that technology to even Mars, let alone anywhere else
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