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Beginner's Guide to Quantum Entanglement
No Fortune writes "Einstein called it 'Spooky action at a distance.' This article describes, in scientific layman's terms, how spooky action is created." From the article: "Normally the photons exit the crystal such that one is aligned in a horizontally (H) polarized light cone, the other aligned vertically (V). By adjusting the experiment, the horizontal and vertical light cones can be made to overlap. Even though the polarization of the individual photons is unknown, the nature of quantum mechanics demands they differ."
Sorry, no. If the coins aren't at the same place, then this term "at that particular instant" is not well defined.
The tantalizing notions of instant communication involve choosing which of two or more possible measurements to make on one of the photons (after they are separated) and the effects of that choice on the possible outcomes of a fixed or independently-chosen experiment on the other photon. Google "EPR Paradox" for a primer.
"But all your emitter and collector are belong to me!"
And the top article on digg links to newsforge, a stablemate of slashdot. I didn't know of any other site which puts in links to newsforge. It's a pretty obscure site outside the slashdot community.
I only had a quick look, and correct me if I am wrong, but digg seems to want people to register to view discussions. From the POV of making money from a site this is a better way to go. So would OSDN care if people moved over to digg? Dunno, have to think about this.
http://michaelsmith.id.au
The article tried to explain it without math, and IIRC that requires some basic trigonomic functions, IIRC Nsin(theta.) Ask most people about trig functions and you will just get a blank stare, or a vague memory of hearing about it in high school. Besides, the entangled photon pair in question are indeed perpendicular to each other, and so the action of polarization at other than 90degrees is a moot point.
I'll never make that mistake again, reading the experts' opinions. - Feynman
It is just that your example is purely classical physics, it is causal, so that the QM entanglement is not shown at all, and QM entanglement for your example is not predicted by any one.
Caused states must not communicate at a distance, this is classical behavior. But, uncaused quantum transitions have the appearance of at-a-distance communication simply because quantum states do not have a classical position. Only the classical manifestations of a quantum state have their separate positions.
Quantum states themselves resemble categorical propositions in their lack of having a location. For example, where is the proposition, "Roses are red.", located? It becomes much more atractive than one first imagines to state that quantum states are actually a sort of categorical propostion.
Michael J. Burns
While we are on the subject of Quantum Mechanics. Check out Caltech's website on Quantum Computers.
I would also like to put you towards HP's Research on it.
The future is quantum mechanics, no matter the subject.
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Brian Greene has a beautiful explanation of how your idea was proven incorrect in The Fabric of the Cosmos. Now comes my horrible attempt to further simplify it so it fits in a Slashdot post.
Your idea would be a fine alternative explanation, if there was only one property being measured. Essentially, there are an infinite number of ways to "stop the coin", different angles if you will. I.e. there are many different properties which can be measured, each of which have the same two possible values. If you measure the same property on both coins, you'll get opposite values, no matter how far apart the coins are.
But suppose you randomly choose which properties to measure on the two coins? You could randomly choose the same property to measure for both, thus guaranteeing the results will be opposite. If you measure two different properties, there's a 50% chance your results will be opposite, because there are only two possible values. Therefore, if these properties are indeed determined before you measure them, you should see opposite values more than 50% of the time.
But that doesn't happen! Experiments have confirmed that the same value is obtained exactly 50% of the time! Thus proving that the values of these properties can't have a pre-determined value.
A and B have agreed that certain measurements of quantum entangled particles will be made a various time intervals as determined by P.
Point C lies between A and B, closer to A than B. C sends quantum entangled particles of definite polarization to A and B. At the agreed-to intervals, A does polarization measuments of particles coming from C; B measures for same polarization at the same interval (accounting for the extra time for the entangle photon to reach B).
Question: does A's collapsing of the state of the entangled photon mean that B will see less entangle photons with that polarization? In other words, will it mean that successful polarization pass-thru's at A's filter has the consequence that B will notice a distinct drop of photons with that polarization passing through its filter? If that were the case, then communication is occuring between A and B in the time it takes for light to travel the shorter distance from C to B.
Change quantum particles to entangle coin tosses. A has the head filter activated, meaning all heads that pass thru A result in no heads at B. With the filter on a A, does B see less heads than he would at other, 'normal', intervals?
If you post it, they will read.
And the polarization of the two polarizing filters that are perpendicular to each other can be defeated by adding a third in-between the others. There are circumstances (adding additional filters) where the polarization depolarizes. The model of polarized light as being filtered through a vertical gate is not wholly correct. It's much more involved. I don't understand it. But I can see how it would affect expected results of the experiment. Just as thinking of electrons as a planetary model is not correct and can lead to false assumptions.
Without going into a long winded explanation, we know that 'spooky action at a distance' (more technically called non-locality) is a real phenomenon based on a theorem called 'Bell's inequality'.
Here's what that theorem says, in fairly simple terms:
If the system is merely the measuring of characteristics that pre-exist, but are unknown (like your pennies), there is a certain statistical distribution that will occur over a series of measurments of those characteristics.
Quantum mechanics predicts a different distribution of the series of measurements.
A substantial number of experiments have demonstrated that the statistical results confirm the non-local explanation of events.
There's a pretty good overview (if a bit technical) of Bell's Theorem here .
Nunc Tutus Exitus Computarus.
The hidden variables theory of quantum mechanics was disproven by a physicists named John Bell. In his method, he began by assuming that these "hidden variables" existed, then, using geometric arguments and the postulates of quantum mechanics, derived a set of inequalities which showed no physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.
It's not intuitive at all, but Bell's argument is sound. Entanglement and action-at-a-distance is real, and not due to the system's state being pre-determined by hidden variables.
/*No comment*/ #No comment
The part that I don't get (so kindly link me to an explanation) is, just because there is no way of measuring where a given particle is, that doesn't mean it's in two places at the same time. It just means we don't know.
What you're hankering after is a "hidden variable model". There is a variable that we can't observe, but it has a definite value. Unfortunately, no simple hidden variable model can explain observations. There are lots of ways of demonstrating this, but all have some complexity.
One of my favourties is due to John Conway and some other people, and it goes like this.
Physics tells us that if we pick any set of three directions at right anfles (eg up, backwards and left) and measure the squared spin of a simple particle (like an electron) in each of them, we get two 0s and a 1 in suitable units. The order of the three measurements doesn't matter.
Now, Conway et al found a set of points on a sphere (ie a set of directions) out of which you can choose lots of triples that are all at right angles. What you can't do is label these points 0 and 1 in such a way that every such triple has two 0s and a 1. So there can't be a hidden variable for the squared spin in each direction, because which one you get depends on which other ones you measure, even though these measurements don't interfere with each other. Using entangled particles and a bit of jiggery pokery you could even do the three measurements at the same time and far apart so there would be no time for information interchange.
A similar, although more subtle effect occurs in EPR. You give each "rocket captain" a choice of directions to measure the polarisation in, and you find a degree of correlation that you could not expect purely from a hidden variable model.
Check Wikipedia for "Bell Test Experiments".
The short answer is yes, of course it has been tested. No one would accept such a theory, or quantum mechanics in general for that matter, without experimental results that agree with its findings.
until you measure one. Firstly, for quantum entanglement to be there, both photons must have come from a single event, like an electron-positron collision. They come out of that event with no particular polarization, but rather a quantum superposition of polarizations. This is evidenced by the fact that they have a 50-50 chance of passing through any polarization filter, regardless of its orientation.
However, once one of them *has* passed through a polarization filter, the other one must have a polarization of 90 degrees of from the other. So if two people distant from one another have two filters set 90 degrees from each other, and if one photon of an entangled pair passes through one filter, the other must pass through the other filter.