Quantum Entanglement

[5614]

im not really sure what category this should come under but anyway:

 

recently i saw in a newspaper that some scientist had teleported the properties of an atom, they'd teleported things before, but nothing as big as an atom and nothing as complex as an atom either

 

here's a link to a website explaining what they did/found:

 

http://news.bbc.co.uk/1/hi/sci/tech/3811785.stm

 

it says that this is an important break through because althought they are still a long way off teleporting humans, they could use it to teleport data in computers instantaniously

 

but what i was interested in was how they did it...

 

they used a method called 'quantum entaglement', by which two atoms were 'bound' to each other's fate! in a sense! so that what happened to one atom, happened to the other, Einstien himself called this very process

"spooky".

 

i was wondering if anyone could tell me more about. explain in detail, but remember that i dont know much about this method, but if you start off with the basics ill soon pick it up!

 

thanks in advanced...

[YT2095]

Thank You!

I`ve been trying to remember those words for about 2 weeks now "Quantum Entanglement" and couldn`t for the life of me remmember what it was called, you`ve just made my day!

[5614]

gr8, you wanted to know the words, now can you tell me what they are, sorry for being so demanding, but its annoying, i wanna know!

[YT2095]

I don`t know how it works either, nor the principlal behind "Entrainment".

I rem seeing an experiment done (first noticed a few 100 years ago) where 2 pendulem clocks were put on a shelf and withing half an hour they were both in perfect synch with each other, no matter how out of phase they were to begin with, and they stayed in perfect synch also!

I wonder if it had anything to do with sympathetic resonance?

 

but I, like yourself, would also love to know alot more about this

[admiral_ju00]

well, for about 18(US) bucks, you can get the full document detailing the whole thing.....

[5614]

nah i dont wanna know all the details, just about quantum entaglement and how it works etc.

 

nb: i started this thread so can i change the title of it to 'quantum entaglement '

[YT2095]

There, changed

[admiral_ju00]

bleh. damnit, i will turn in my request for the Nature subscription!!!

 

but here's what i found googling for: quantum entaglement

 

Quantum Entanglement

In 1935 and 1936, Schrödinger published a two-part article in the Proceedings of the Cambridge Philosophical Society in which he discussed and extended a remarkable argument by Einstein, Podolsky, and Rosen. The Einstein-Podolsky-Rosen (EPR) argument was, in many ways, the culmination of Einstein's critique of the orthodox Copenhagen interpretation of quantum mechanics, and was designed to show that the theory is incomplete. In classical mechanics the state of a system is essentially a list of the system's properties — or, more precisely, it is the specification of a set of parameters from which the list of properties can be reconstructed: the positions and momenta of all the particles comprising the system. The dynamics of the theory specifies how properties change in terms of a law of evolution for the state. Pauli characterized this mode of description of physical systems as a ‘detached observer’ idealization (see Pauli's letter to Born in The Born-Einstein Letters, p. 218). On the Copenhagen interpretation, such a description is not possible for quantum systems. Instead, the quantum state of a system should be understood as a catalogue of what an observer has done to the system and what has been observed, and the import of the state then lies in the probabilities that can be inferred (in terms of the theory) for the outcomes of possible future observations on the system. Einstein rejected this view and proposed a series of arguments to show that the quantum state is simply an incomplete characterization of the system. The missing parameters are sometimes referred to as ‘hidden parameters’ or ‘hidden variables’ (although Einstein did not use this terminology, presumably because he did not want to endorse any particular ‘hidden variable’ theory).

It should not be supposed that Einstein's definition of a complete theory included the requirement that it be deterministic. Rather, he required certain conditions of separability and locality for composite systems consisting of separated component systems: each component system separately should be characterized by its own properties (even if these properties manifest themselves stochastically), and it should be impossible to alter the properties of a distant system instantaneously (or the probabilities of these properties) by acting on a local system. In later analyses — notably in Bell's extension of the EPR argument — it became apparent that these conditions, suitably formulated as probability constraints, are equivalent to the requirement that statistical correlations between separated systems should be reducible to a common cause in the sense of Reichenbach.

 

In the original EPR article, two particles are prepared from a source in a certain quantum state and then move apart. There are ‘matching’ correlations between both the positions of the two particles and their momenta: a measurement of either position or momentum on a particular particle will allow the prediction, with certainty, of the outcome of a position measurement or momentum measurement, respectively, on the other particle. These measurements are mutually exclusive: either a position measurement can be performed, or a momentum measurement, but not both simultaneously. Either correlation can be observed, but the subsequent measurement of momentum, say, after establishing the position correlation, will no longer yield any correlation in the momenta of the two particles. It is as if the position measurement disturbs the correlation between the momentum values. The puzzle is that the quantum state of the particle pair is inconsistent with any assignment of precise position and momentum values to the particles separately. These values would be the common cause of the correlations, and would provide an explanation of the correlations in terms of the initial correlations between the properties of the two systems at the source. EPR concluded that the quantum state was incomplete.

 

Here is how Schrödinger put the puzzle in the first part of his two-part article (Schrödinger, p. 559):

 

Yet since I can predict either x1 or p1 without interfering with the system No. 1 and since system No. 1, like a scholar in an examination, cannot possibly know which of the two questions I am going to ask first: it so seems that our scholar is prepared to give the right answer to the first question he is asked, anyhow. Therefore he must know both answers; which is an amazing knowledge; quite irrespective of the fact that after having given his first answer our scholar is invariably so disconcerted or tired out, that all the following answers are ‘wrong.’

What Schrödinger showed was that if two particles are prepared in a quantum state such that there is a matching correlation between two ‘canonically conjugate’ dynamical quantities — quantities like position and momentum whose values suffice to specify all the properties of a classical system — then there are infinitely many dynamical quantities of the two particles for which there exist similar matching correlations: every function of the canonically conjugate pair of the first particle matches with the same function of the canonically conjugate pair of the second particle. Thus (p. 559) system No. 1 ‘does not only know these two answers but a vast number of others, and that with no mnemotechnical help whatsoever, at least with none that we know of.’

 

Schrödinger coined the term ‘entanglement’ to describe this peculiar connection between quantum systems (Schrödinger, p. 555):

 

When two systems, of which we know the states by their respective representatives, enter into temporary physical interaction due to known forces between them, and when after a time of mutual influence the systems separate again, then they can no longer be described in the same way as before, viz. by endowing each of them with a representative of its own. I would not call that one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought. By the interaction the two representatives [the quantum states] have become entangled.

He added (Schrödinger, p. 555):

 

Another way of expressing the peculiar situation is: the best possible knowledge of a whole does not necessarily include the best possible knowledge of all its parts, even though they may be entirely separate and therefore virtually capable of being ‘best possibly known,’ i.e., of possessing, each of them, a representative of its own. The lack of knowledge is by no means due to the interaction being insufficiently known — at least not in the way that it could possibly be known more completely — it is due to the interaction itself.

Attention has recently been called to the obvious but very disconcerting fact that even though we restrict the disentangling measurements to one system, the representative obtained for the other system is by no means independent of the particular choice of observations which we select for that purpose and which by the way are entirely arbitrary. It is rather discomforting that the theory should allow a system to be steered or piloted into one or the other type of state at the experimenter's mercy in spite of his having no access to it.

 

In the second part of the paper, Schrödinger showed that, in general, a sophisticated experimenter can, by a suitable choice of operations carried out on one system, steer the second system into any ‘mixture’ of quantum states he chooses, i.e., not steer the system into any one particular state, but constrain the state into which the system evolves to lie in a given set, and at the same time fix the probabilities with which the system evolves into the states from the given set. He found this conclusion sufficiently unsettling to suggest that the entanglement between two separating systems would persist only for distances small enough that the time taken by light to travel from one system to the other could be neglected, compared with the characteristic time periods associated with other changes in the composite system. He speculated that for longer distances each of the two systems might in fact be in a state associated with a certain mixture, determined by the precise form of the entangled state.

 

Most physicists dismissed the puzzling features of entangled quantum states as an artefact of Einstein's inappropriate ‘detached observer’ view of physical theory, and regarded Bohr's reply to the EPR argument as vindicating the Copenhagen interpretation. This was unfortunate, because the study of entanglement was ignored for thirty years until John Bell's reconsideration and extension of the EPR argument. Bell looked at entanglement in simpler systems than the EPR case: matching correlations between two-valued dynamical quantities, such as polarization or spin, of two separated systems in an entangled state. What Bell showed was that the statistical correlations between the measurement outcomes of suitably chosen different quantities on the two systems are inconsistent with an inequality derivable from Einstein's separability and locality assumptions — in effect from the assumption that the correlations have a common cause.

 

Bell's investigation generated an ongoing debate on the foundations of quantum mechanics. One important feature of this debate was confirmation that entanglement can persist over long distances(see Aspect et al.), thus falsifying Schrödinger's supposition of the spontaneous decay of entanglement as two entangled particles separate. But it was not until the 1980s that physicists, computer scientists, and cryptographers began to regard the non-local correlations of entangled quantum states as a new kind of non-classical resource that could be exploited, rather than an embarrassment to be explained away. (For further discussion of entanglement as a physical resource, including measuring entanglement, and the manipulation and purification of entanglement by local operations, see "The Joy of Entanglement" by Popescu and Rohrlich in Lo, Popescu, and Spiller, or Nielsen and Chuang.)

[swansont]

Not to diminish the accomplishment, which is significant, but note that what happened what a teleportation of the atom's state, and not the atom itself. The atom wasn't moved across the room (or whatever) - the information contained in it, by virtue of being in a particular state - was.

[YT2095]

agreed, create a duplicate and destroy the original spings to mind from another recent thread.

however, the idea of such information (for wants of a better word) being passed from one entity to another is quite astonishing, I think you`ve agreed on that.

what are the possible implications of it though?

[Dave]

I think the article says something about it being used in quantum computing.

[5614]

yeah, the original article:

 

http://news.bbc.co.uk/1/hi/sci/tech/3811785.stm

 

says that this could be used for quantum computing

eg.

"teleporting" data immediately, without a time delay as there is at the moment, it would revolutionise the way that internet and networks work!

[TheProphet]

Not to diminish the accomplishment, which is significant, but note that what happened what a teleportation of the atom's state[/i'], and not the atom itself. The atom wasn't moved across the room (or whatever) - the information contained in it, by virtue of being in a particular state - was.

 

But i wounder really how sure they are on that fact! Altough i find it too be the most possible and logical explenation! It could also be so that they really transported the particles themselves.. like a none earning, nothing done slingshoot split! String theory might hold the answer! But the question i like to ask is: I have to coins in my table, same labels and date: If the were to change place instantly i wouldn't be able to tell the differnce! This is for me a most possible outcome!

[ydoaPs]

it didn't teleport, it changed the properties of the other atom. if you were to say rip off an electron, the other would also lose an electron

[ceres]

agreed' date=' create a duplicate and destroy the original spings to mind from another recent thread.

however, the idea of such information (for wants of a better word) being passed from one entity to another is quite astonishing, I think you`ve agreed on that.

what are the possible implications of it though?[/quote']

 

A few years back i read a short story(scifi) i cant for the life of me remember the name or the author but it brought up the idea of when our bodies grow old our brains be "copied" and moved into a fresh new body to basically create ever lasting life. If this recent finding can be matched to a technology capable to map every cell in a human brain, who knows where things could end up.

 

The only point i wondered about when you transfers states (i.e. copy my old brain into a new body) would you be technially dead and are basically a new person when you are remade?

 

Complete conjecture but it's something to think about when your bored at work

[5614]

is quantum entaglement limited to a short distance, or could you "teleport" the atom anywhere...... i know you are 'copying' the atom, not actually telelporting it, but is it do-able over any distance?

[Guest yamum]

so deos this mean that if u move one left the other would move the same, so deos this mean that you could 1 place in the world and have a doulbe would some where alse doing the same as you

[Cap'n Refsmmat]

No, it means that the PROPERTIES of the atoms are the same, so you alter the spin of one and the other changes as well.

 

Or so I believe.

[jordan]

Maybe I'm thinking of something else, but I thought that the stuff Cap'n was talking about was a little different. My understanding was that the particles will start off the with two related properties. When we decide to measure one, we can instantly determine the state of the other, even if it's lightyears away. Through this method, you have learned the state of a particles that is lightyears away in an instant. Like I said, though, this could be something different than what you're talking about Cap'n.

[TheProphet]

Maybe I'm thinking of something else, but I thought that the stuff Cap'n was talking about was a little different. My understanding was that the particles will start off the with two related properties. When we decide to measure one, we can instantly determine the state of the other, even if it's lightyears away. Through this method, you have learned the state of a particles that is lightyears away in an instant. Like I said, though, this could be something different than what you're talking about Cap'n.

 

No.. Entagneld particles propably behaves like this! but since i have no way to prove i'll just say that Einstein thought his head to pieces over this! So the particles willl behave like Cap'n said!

[jordan]

I don't follow.

[5614]

can sum1 explain the difference between entangled atoms or particles AND quantum entaglement.....

 

i understand all about quantum entaglment used to "teleport" and atom

and

about entagled atoms..... where they 'mirror' each other, even though they are not connected [physically]

 

but whats the difference, y r they under the same name 'entaglement' is their a connection..... other than that in quantum entaglement as i know it the atom's properties are copied to another place, then the original destroyed....

 

coz when i read about quantum entaglement they were using the method to "teleport" an atom, now ur talking about, the same method to make the atoms entangled, without copying the original, so it doesnt need to be destroyed

 

im confused !

[TheProphet]

can sum1 explain the difference between entangled atoms or particles AND quantum entaglement.....

 

i understand all about quantum entaglment used to "teleport" and atom

and

about entagled atoms..... where they 'mirror' each other' date=' even though they are not connected [physically']

 

but whats the difference, y r they under the same name 'entaglement' is their a connection..... other than that in quantum entaglement as i know it the atom's properties are copied to another place, then the original destroyed....

 

coz when i read about quantum entaglement they were using the method to "teleport" an atom, now ur talking about, the same method to make the atoms entangled, without copying the original, so it doesnt need to be destroyed

 

im confused !

 

They teleported information (an atoms state)! In this case it whas probably the spin of an atom.. that way u can simulate digital 1 and 0! The original wasen't destoryed since they never teleported the whole atom nor anything physical just a state...

As far as i can tell there is no physical link.. may it be that there is or not.. but atleast we can't see it with todays technology!

And Yes they mirror each other without having to really hold each hands!

 

Jordan: What do u not understand?

[5614]

but in:-

http://news.bbc.co.uk/1/hi/sci/tech/3811785.stm

 

[go to the bottom of the above pg, for pic]

 

it says:

 

Atomic dance

 

What the teams at the University of Innsbruck and the US National Institute of Standards and Technology (Nist) did was teleport qubits from one atom to another with the help of a third auxiliary atom.

 

It relies on a strange behaviour that exists at the atomic scale known as "entanglement", whereby two particles can have related properties even when they are far apart. Einstein called it a "spooky action".

 

The two groups used different techniques for achieving teleportation, but both followed the same basic protocol.

 

First, a pair of highly entangled, charged atoms (or ions) are created: B and C. Next, the state to be teleported is created in a third ion, A.

 

Then, one ion from the pair - let's say B - is entangled with A. The internal state of both these is then measured and the result sent to ion C.

 

This transforms the quantum state of ion C into that created for A, destroying the original quantum state of A.

 

The teleportation took place in milliseconds and at the push of a button, the first time such a deterministic mechanism has been developed for the process.

 

so it was destroyed, unless the BBC r wrong, or more prob, we're talking about different things, so thats what i was saying in the 1st place, i know what you said just now, but whats the difference where one was copied, then destroyed, and thus "teleported" and where they are just made to mirror each other

[jordan]

Jordan: What do u not understand?

You said something about you not being able to prove it yet, plus something about Einstein and you came out with the conclusion that Cap'n is right. I didn't follow the logical progression.