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Poponfu
2008-Feb-13, 01:57 AM
Two particles were entangled and one placed on my sweet spaceship that goes .75c . Would they still influence each other instantaneously or would there be a delay or dilation of sorts. Or maybe this is stuff that cant even be predicted ?

Noclevername
2008-Feb-13, 02:20 AM
Two particles were entangled and one placed on my sweet spaceship that goes .75c . Would they still influence each other instantaneously or would there be a delay or dilation of sorts. Or maybe this is stuff that cant even be predicted ?

As far as I understand, the influence itself is simultaneous, but being able to figure out what has changed requires comparing the two, which still relies on communicating information which is limited to lightspeed. So no instant messaging across the galaxy.

Poponfu
2008-Feb-13, 02:37 AM
oops dbl post

Poponfu
2008-Feb-13, 02:40 AM
If this experiment here did indeed prove to be true wouldn't that allow a way for information to be exchanged between earth and said spacecraft.

http://www.physorg.com/news113824784.html

Noclevername
2008-Feb-13, 02:50 AM
If this experiment here did indeed prove to be true wouldn't that allow a way for information to be exchanged between earth and said spacecraft.

http://www.physorg.com/news113824784.html

I'm not knowledgeable enough on the subject to judge. But note that they still had to observe and compare both particles to notice the interaction. If one particle is on a starship, you'll still have to get information about the state of the homebound particle through standard lightspeed channels to compare them in order to to "read" the entangled-state message.

Poponfu
2008-Feb-13, 08:32 AM
Thanks Noclevername , after you told me that I read lots more and I get what you are saying now.

I stumbled upon this and cant understand some parts of the setup he is proposing can anyone help me out ?

http://arxiv.org/PS_cache/quant-ph/pdf/0505/0505204v2.pdf

VV


The suggested superluminal telecommunication system based on entangled photon pairs is schematically illustrated in Figs. 1, 2 and 3. This system consists of three components: a source of polarization entangled photon pairs, a signal encoder, and a signal decoder. Binary signals are transmitted in this telecommunication system.

During telecommunication processes, polarization entangled photon pairs are generated at the source S. One of the two entangled photons is sent to the signal sender, and the other one is sent to the signal receiver. The signalencoder placed at the signal sender include a mirror (M) which can be switched between the position labeled “0” and the position labeled “1”, and two photon detector channels: the channel “0” and the channel “1”. There are one Glan-Thompsom prism and two single photon detectors in each channel. The Glan-Thompsom prism (BS0) in the channel “0” is arranged in such a way that the photons detected by the photon detector D0 are horizontally polarized, the photons detected by the photon detector D′ 0 are vertically polarized. The Glan-Thompsom prism (BS1) in the channel “1” is rotated 45◦, so the photons detected by the photon detector D′1 are polarized at 45◦ to horizontal direction, and photons detected by the photon detector D′ 1 are polarized at −45◦ to horizontal direction.
http://airportvillas.com/img/figures.jpg


The signal receiver is equipped with the signal decoder that includes an optical amplifier (OA), a spatial filter (SF) that allows only photons in the same spatial mode as the incident photon to pass, a Glan-Thompsom prism (BSr) placed at the output end of the optical amplifier which splits an optical beam into horizontally polarized and vertically polarized secondary beams. Two single photon detectors (Dr and D′r) are placed in each of these two secondary beams. The photon counts by the detectors Dr and D′r are analysed by the signal analyser, and converted to the signal readout.


When a photon entered in the OA, stimulated and spontaneous emissions both take place. As just one photon is present, the stimulated emitting rate equals the spontaneous emitting rate for photons with the same polarization as the incident photon. At the same time, photons with polarization perpendicular to the polarization incident photon are also generated, at the same spontaneous emitting rate. So the optical beam that passes the spatial filter (SF) contains 2m + 1 photons with the same polarization as the incident photon, and m photons with perpendicular polarization. In other words, an incident photon is amplified by OA into a partial polarized optical beam. The characteristic of this partial polarized optical beam depends on the polarization of the incident photon.

To send a binary signal “0”, the sender switches the mirror M into the position “0”. In this case the photon sent to the sender can be detected either by D0 or by D′0. Once the photon being detected, the polarization of the photon sent to the receiver is also determined: it must be either horizontally polarized or vertically polarized. The whole system can be setup in such a way that the polarization of the photon sent to the receiver is determined when it arrives at the receiver. This “signal carrier” photon passes the optical amplifier OA, where 2m more photons with the same polarization as the “signal carrier” photon and m photon with perpendicular polarization are generated. In the case of sending the signal “0”, 2m + 1 photons with the same polarization as the “signal carrier” photon are detected by one of the detectors Dr and D′r, and m photons with perpendicular polarization are detected by another detector. A difference of m + 1 in photon counts by the detectors Dr and D′r
corresponds to a binary signal “0” at readout, and the signal “0” is received in this way.


Theres lots more to it , he explains how "1s" are sent and that there is a expected error rate.

The questions I have well theres plenty but two are: what role does the optical amplifier play in the decoder and how does it help keep errors down somehow? ( that second part is only if you read more into it )

I have lots more but just wanna see what someone says first

sk8rpinoi32
2008-Feb-13, 08:48 AM
Look up the seamless whole theory, or Bell's Theorem. Or Bohm's interpretation.

From what I understand, there is a universe that lies beneath us. Particles in our dimension appear to be seperate, but in the seamless whole universe, they are actually 1. Thus the plausibility of acting simultaneously.

rtomes
2008-Feb-13, 10:31 AM
Two particles were entangled and one placed on my sweet spaceship that goes .75c . Would they still influence each other instantaneously or would there be a delay or dilation of sorts. Or maybe this is stuff that cant even be predicted ?

There is no instantaneous influence involved in entanglement. No information is ever passed between entangled states. The only thing is that they were created with some properties that are related but we don't know the relationship. It is purely a statistical connection based on our lack of knowledge. You cannot pass information instantaneously and the experts agree on this.

Ken G
2008-Feb-13, 12:24 PM
Noclevername and rtomes are right on track here-- the oft-overlooked problem with calling it an "instantaneous influence" is that you always need independent information from both particles before you see anything strange, and that requires subluminal communication. The idea that there could be "instantaneous" influences suffers from the problem that the different reference frames of two particles cannot even agree on the meaning of what "instantaneous" means (as per relativity). It's not so easy to see where this all plays out in that quoted material, Poponfu (and by the way we usually just use links, I don't think you're supposed to lift verbatim chunks of that text), but there's going to be an error in their analysis. It's too late at night for me to look for it right now, perhaps someone else can point it out explicitly.

sk8rpinoi32
2008-Feb-13, 09:12 PM
There is no instantaneous influence involved in entanglement. No information is ever passed between entangled states. The only thing is that they were created with some properties that are related but we don't know the relationship. It is purely a statistical connection based on our lack of knowledge. You cannot pass information instantaneously and the experts agree on this.

That isn't correct. It's true nothing can go fast than the speed of light. In instantanism does occur as in this entanglement problem. Bell does prove that electrons that are entangle do spin instantaneously.

rtomes
2008-Feb-13, 09:41 PM
That isn't correct. It's true nothing can go fast than the speed of light. In instantanism does occur as in this entanglement problem. Bell does prove that electrons that are entangle do spin instantaneously.

The only instant involved is the one where, after the two sets of data are brought together at sub-luminal speed, the results are compared. The whole of Bell's inequality is based on a failure to understand the difference between a statistical sample and a subsample. The apparently strange result is due to ignoring data from one source when there is no detection at the other one. Any decent statistician who looks at the data treatment will confirm this.

I don't know what you mean by "do spin instantaneously". I assume you mean that they change spin when the other one is measured. This is just plain wrong. Produce some evidence for this please.

Poponfu
2008-Feb-13, 10:16 PM
Noclevername and rtomes are right on track here-- the oft-overlooked problem with calling it an "instantaneous influence" is that you always need independent information from both particles before you see anything strange, and that requires subluminal communication. The idea that there could be "instantaneous" influences suffers from the problem that the different reference frames of two particles cannot even agree on the meaning of what "instantaneous" means (as per relativity). It's not so easy to see where this all plays out in that quoted material, Poponfu (and by the way we usually just use links, I don't think you're supposed to lift verbatim chunks of that text), but there's going to be an error in their analysis. It's too late at night for me to look for it right now, perhaps someone else can point it out explicitly.


Oh sorry , thanks for the explanation Ken G. I did have a idea of how they could overcome the time dilation between them but its probably pretty ridiculous so... sorry I quoted all of that. It was really just the stuff I wanted you guys to see but next time I will just linkie. Are you awake enough to try and answer what that paper is all about yet ?

am I just not absorbing enough from it ? I thought it was simple as if I get more of these its a "0" bit and more of these its a "1" with a certain error rate.

Poponfu
2008-Feb-13, 10:29 PM
The only instant involved is the one where, after the two sets of data are brought together at sub-luminal speed, the results are compared. The whole of Bell's inequality is based on a failure to understand the difference between a statistical sample and a subsample. The apparently strange result is due to ignoring data from one source when there is no detection at the other one. Any decent statistician who looks at the data treatment will confirm this.

I don't know what you mean by "do spin instantaneously". I assume you mean that they change spin when the other one is measured. This is just plain wrong. Produce some evidence for this please.



I don't get it isn't this proven already to occur ? for these " polarization entangled photon pairs " where if A goes through one gate then B HAD to go through a certain one ?

Ken G
2008-Feb-14, 06:18 AM
Poponfu, I've looked over both those linked articles, and I don't find either one very convincing though it is hard to locate the error without considerable effort. The first article is written for a popular audience, so doesn't really give the physics that would be needed to judge it, but to me it has the flavor of an explanation that is being parroted by someone who doesn't really understand it themself, like a journalist rather than a physicist. That means it carries no insights into the physics that I could use to find the flaw-- it just claims that certain things will happen in certain circumstances, and then reaches conclusions based on that. What I do find more reasonable are the direct quotes from the authors of the study, which do seem to make sense, but are far less grandiose than the claims of the popular article. In a nutshell, the authors claim their study shows that the information is encoded in the fields not in the particles themselves, but that is kind of quantum mechanics 101. The opposite conclusion would have been the surprise, as we'd need new quantum mechanics-- as it is, quantum mechanics comes through fine. But there's no hint of any superluminal communication, for just the reasons mentioned by Noclevername and rtomes above.

The second link is almost certainly pure bunk, but it would be a lot of work for me to tease out where the error is because the author makes claims that are not clearly explained. The key claim is that one polarization produces 2m+1 photons at one detector, and m at the other, while the other produces 2m at one and m at the other. I understand the 2m versus m, that's just the amplification m times the spontaneous or stimulated plus spontaneous emissions. But I don't know why he argues he can get 2m+1 and m the other way, and that difference is the key to the whole thing. I think it is probably wrong right there, but if not-- then somewhere else.

To me, the bottom line about entanglement is that "wave functions" tell particles where to go, so the information is in the wave functions, not the particles. Particles are essentially mindless quanta that just show up where they are supposed to with the attributes the wave function tells them to have. Wave functions, on the other hand, are inherently nonlocal entities, so it's no surprise that they encode information nonlocally. But you cannot extract anything but local information from a wave function, so there is no "influence" at a distance, that simply comes from imagining that the information is in the particles. The fact that the wave function changes globally when you make a measurement locally is only information that exists in your own head-- and so it stays perfectly local until you correlate with nonlocal observations. The act of correlation extracts the nonlocal information from the wave function, it is not an "influence" because the correlation requires normal subluminal communication. There is almost certainly no way to get superluminal communication with entanglement, and I don't find either article convincing that they can.