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sarongsong
2003-Jun-21, 05:31 AM
"WASHINGTON -- A noted group of Austrian scientists yesterday reported the first long-distance demonstration of "quantum entanglement" through open space -- a baby step toward possibly someday sending objects to distant places in "beam-me-up-Scotty" transport machines and performing other science-fiction marvels..."
http://www.post-gazette.com/healthscience/20030620quantumsci2.asp

beskeptical
2003-Jun-21, 06:46 AM
Both particles might start with a positive electric charge and then be separated by a billion miles. But if the charge in one is changed to negative, so is the other's, in virtually the same instant. Somehow, the information travels from one particle to the other faster than the speed of light.
This kind of stuff is so fascinating. I don't know why anyone needs fake mysteries like crop circles.

sarongsong
2003-Jun-21, 07:24 AM
Quite agreed, but...it's about that 2nd picture here, then... I see the mystery part OK, just haven't quite mastered the fake part.
http://www.cccrn.ca/thephenomenon.html

pixelator
2003-Jun-21, 03:24 PM
So how can the quantum particles communicate their states faster than light? doesn't that violate general relativity or something?

So basically if you could modulate the quantum particles' states at one end and demodulate it at the other end, you could get an FTL communications device? Subspace radio just like Star Trek (but even faster). cool.

Maybe SETI should stop wasting time seeking intelligent life using radio telescopes and start looking for a way to "tap" into quantum communications. Seems like that would be the way aliens would be using to communicate if they are out there and are more advanced than us.

eburacum45
2003-Jun-21, 04:31 PM
Quantum Entanglement does not seem to carry any useful data which can be used to send a message; however a related phenomenon , Quantum Teleportation, can transfer information at light speed, and it may be possible to use this phenomenon to send messages with improved accuracy and less chance of interception.
Or it may not.
http://www.wikipedia.org/wiki/Quantum_entanglement
http://www.wikipedia.org/wiki/Quantum_teleportation

sarongsong
2003-Jun-21, 04:42 PM
pixielator:

So how can the quantum particles communicate their states faster than light?
Anybody know the speed of thought?

pixelator
2003-Jun-21, 06:09 PM
I did some searching on the net and found some interesting articles:

One from IBM about quantum teleportation:
http://www.research.ibm.com/quantuminfo/teleportation/

And one about using some weird forbidden zone microwaves to send mozart at 4.7x light speed:

a bit long, published by New Scientist on april 1, 1995 but further reading and searching finds it is not an april fools joke.

http://www.socorro.demon.co.uk/gunter.htm


To an astonished audience, Nimtz announced that his team at Cologne had not only measured superluminal speeds for their microwaves, but had actually sent a signal faster than light. The signal in question was Mozart's 40th Symphony. What they did was frequency modulate their microwave source with the music and then measure how quickly the music arrived after traversing the forbidden zone in a waveguide. According to Nimtz, Mozart's 40th hopped across 12 centimetres of space at 4.7 times the speed of light. What's more, Nimtz actually had a recording to prove it. To his now bemused audience, he played a tape in which among the background hiss strains of Mozart could be heard. This was the "signal" that had travelled faster than light.

pixelator
2003-Jun-21, 06:21 PM
Both particles might start with a positive electric charge and then be separated by a billion miles. But if the charge in one is changed to negative, so is the other's, in virtually the same instant. Somehow, the information travels from one particle to the other faster than the speed of light.
This kind of stuff is so fascinating. I don't know why anyone needs fake mysteries like crop circles.

I agree. We live in an amazing time.

OK if the charges change instantly, and there must be a way to measure this, otherwise how would the scientists verify the effect is happening, then in theory you should be able to send a binary signal instantaneously by changing the charge on one particle, flipping it positive and negative.
So you should be able to encode information (such as morse code) in such a signal, and therefore get FTL communication.

Even if the thing only works for 1 change (if for instance it destroyed the original particle during the experiment) you could still use it to communicate a message FTL.

Here is a thought experiment: Captains Kirk and Picard have a quantum entangled pair. Picard tells Kirk to go to the other side of the galaxy to watch for a borg attack. If he sees one, tweak the particle. So, when Picard sees his particle tweak, he knows the borg are on their way. This is useful information, and it was transmitted instantly, FTL. Kinda like a quantum FTL Paul Revere signal. :)

TriangleMan
2003-Jun-21, 08:30 PM
I read a book a few months back titled Entanglement that delved into the whole quantum entanglement process. It seems really weird that if a change happens to one entagled particle the other one will also be affected regardless of the distance. However I still can't get over the illogicalness of the double-slit experiment findings (you know, that old experiment where the photon must be going through both slits at the same time) so if evidence of entanglement is starting to come forth here's hoping it becomes useful.

daver
2003-Jun-21, 11:34 PM
pixielator:

So how can the quantum particles communicate their states faster than light?
Anybody know the speed of thought?

That's not particularly well defined, nor particularly useful. I suppose you could try to determine the signal propagation speed in an non-myelinated neuron. I'd guess on the rough order of a few hundred meters/second.

RafaelAustin
2003-Jun-21, 11:41 PM
Maybe SETI should stop wasting time seeking intelligent life using radio telescopes and start looking for a way to "tap" into quantum communications. Seems like that would be the way aliens would be using to communicate if they are out there and are more advanced than us.

8) I agree! Searching the radio band is just looking for someone at our tech level lowering our odds significantly.

dgruss23
2003-Jun-21, 11:43 PM
Just to be sure - quantum entanglement is predicted by quantum mechanics but contradicts relativity in that it implies faster than light communication - right?

RafaelAustin
2003-Jun-21, 11:45 PM
Here is a thought experiment: Captains Kirk and Picard have a quantum entangled pair. Picard tells Kirk to go to the other side of the galaxy to watch for a borg attack. If he sees one, tweak the particle. So, when Picard sees his particle tweak, he knows the borg are on their way. This is useful information, and it was transmitted instantly, FTL. Kinda like a quantum FTL Paul Revere signal. :)

OK, take the experiment one step further: make a massively parrallel system based on thousands or millions of predefined pairs. Each pair would represent a different symbol, command, expression, etc. And there you have an Entanglement Chip!

RafaelAustin
2003-Jun-21, 11:48 PM
Just to be sure - quantum entanglement is predicted by quantum mechanics but contradicts relativity in that it implies faster than light communication - right?

Einsetin called it ”Spooky Actions at a Distance”. He didn't like it.

pixelator
2003-Jun-22, 12:48 AM
Maybe SETI should stop wasting time seeking intelligent life using radio telescopes and start looking for a way to "tap" into quantum communications. Seems like that would be the way aliens would be using to communicate if they are out there and are more advanced than us.

8) I agree! Searching the radio band is just looking for someone at our tech level lowering our odds significantly.

That, plus if they are anything like us, they are just sitting there listening also and not transmitting anything other than stray TV/Radio signals like us. We don't send out anything, but just listen hoping for someone else out there to be sending. If they aren't we won't hear anything. I doubt stray TV or Radio signals would propagate very well or far outside the atmosphere. They are meant to be local signals and as anyone with a TV antenna knows they don't propagate very well even where they are supposed to.

I bet if we ever do find intelligent signals it will be using some new technology like the quantum entanglement thing or something we haven't even thought of yet.

djsmeg
2003-Jun-22, 02:58 AM
Unfortunately, I thought that communication via entanglement cannot take place super-luminally. The problem is that you need the output result from experimenting (tweaking) the first of the photons, to be able to decipher the message on the second one.

This appears to explain the use of entanglement in teleportation and explain the really odd EPR experiment (spooky action at a distance) (http://plato.stanford.edu/entries/qt-entangle/#2)

pixelator
2003-Jun-22, 03:26 AM
Wow. My head hurts after reading that!

It's a bit over my head, but two questions:

1. If you can't determine the state of the second entangled photon directly, but need the information from the first one (the tweaker) to tell you what the new state is, then how do they verify that the second photon really did follow the first photon's 'tweak'?

2. Does anyone know by what method the information is passed between the entangled pairs? Some force? Magic? :)

eburacum45
2003-Jun-22, 08:11 AM
To recap- As far as I understand it quantum communication can only send meaningful information at lightspeed (or perhaps below), so Pickard and Kirk would not be able to hear each other;
it may be useful for increasing information flow at light speed at long distances;
however the (separate) quantum tunnling effect has to take place in solid objects, so would be no good for interplanetary messaging.

beskeptical
2003-Jun-22, 09:16 AM
Quite agreed, but...it's about that 2nd picture here, then... I see the mystery part OK, just haven't quite mastered the fake part.
http://www.cccrn.ca/thephenomenon.html

Starting a debate on crop circles here would be hyjacking the thread. I tried to use an example that wouldn't start a debate but apparently I failed. The pictures of different appearances of wheat stalks have other explanations and don't support the circles being of supernatural origin. People have not only admitted making the circles but they have also demonstrated making them. The stalks from manmade circles were shown to the 'experts' claiming stalks differed and the experts said the stalks were from true circles.

If you want to discuss this topic, start another thread and I'm sure you will have responses. The link is interesting.

beskeptical
2003-Jun-22, 09:19 AM
Unfortunately, I thought that communication via entanglement cannot take place super-luminally. The problem is that you need the output result from experimenting (tweaking) the first of the photons, to be able to decipher the message on the second one.

This appears to explain the use of entanglement in teleportation and explain the really odd EPR experiment (spooky action at a distance) (http://plato.stanford.edu/entries/qt-entangle/#2)

Oooh, that's an interesting link.

kilopi
2003-Jun-22, 09:24 AM
Maybe SETI should stop wasting time seeking intelligent life using radio telescopes and start looking for a way to "tap" into quantum communications. Seems like that would be the way aliens would be using to communicate if they are out there and are more advanced than us.

8) I agree! Searching the radio band is just looking for someone at our tech level lowering our odds significantly.
Yeah, take all that SETI money and start using it to develop quantum communication systems. That should only take about 10^7 years, at the current level of funding. :)

djsmeg
2003-Jun-23, 01:45 AM
Wow. My head hurts after reading that!

You're in good company. I think it was Richard Feynman who said that if your brain doesn't hurt when trying to understand quantum mechanics, you don't understand it. :)


It's a bit over my head, but two questions:

1. If you can't determine the state of the second entangled photon directly, but need the information from the first one (the tweaker) to tell you what the new state is, then how do they verify that the second photon really did follow the first photon's 'tweak'?


Umm, this is related to something called "Bell's inequality" IIRC. The idea is something like this:

If I get a three state entanglement (such as photon A being red, green or blue, then photon A' is entangled to not-red, not-green or not-blue, so adopts one of the other colours with 50/50 probability) then what I can do is measure the probability that A is blue. If they are not entangled then I will get an probability of A' being not-blue of 33%. But if they are it's 50% (IIRC). Experiments have verified that it is the latter- i.e. they are entangled.


2. Does anyone know by what method the information is passed between the entangled pairs? Some force? Magic? :)

No one knows. Some have speculated tachyons (faster than light particles), others consider it a mystery which a deeper understanding of the real mechanisms of quantum mechanics will uncover. I think there's a "many-universes" answer as well, but I don't know what it might be.

By the way, the book I got all this from was "The Quest for the Quantum Computer" which has excellent layman's descriptions of entanglement as well as some fascinating applications.

pixelator
2003-Jun-23, 04:11 PM
Thanks djsmeg.

Yep. Brain-aches definately accompany quantum mechanics. The complete non-intuitiveness of QM is part of what I like about it. Makes ya think. But at the same time, it makes you wonder, "IF this is so counter-intuitive and complex, I wonder if we are missing out on a much simpler answer?"

It kind of reminds be of the complex theories the old geocentric astronomers had to come up with to explain the planetary orbits, and then along comes Galileo and simplifies everything by putting the sun in the center instead of the earth.

I wonder if some similar shift in perspective, so to speak, will one day simplify quantum mechanics and everyone will do an 'Homer Simpson' and say: "Doh! Why didn't we think of that before?"

djsmeg
2003-Jun-23, 06:57 PM
Thanks djsmeg.
You're welcome.


Yep. Brain-aches definately accompany quantum mechanics. The complete non-intuitiveness of QM is part of what I like about it. Makes ya think. But at the same time, it makes you wonder, "IF this is so counter-intuitive and complex, I wonder if we are missing out on a much simpler answer?"

It kind of reminds be of the complex theories the old geocentric astronomers had to come up with to explain the planetary orbits, and then along comes Galileo and simplifies everything by putting the sun in the center instead of the earth.

I wonder if some similar shift in perspective, so to speak, will one day simplify quantum mechanics and everyone will do an 'Homer Simpson' and say: "Doh! Why didn't we think of that before?"

Sadly, I do not think this is going to happen. The thing is, when you contemplate the maths, QM actually appears relatively simple (mathematically speaking). It's the results that are counter-intuitive.

Ironically, the other "great" 20th century physics counterpart to QM, General Relativity, is relatively complex mathematically (at least it appears to be to me) but its results are wonderfully intuitive (rubber sheets etc).

Intuition is not all it's cracked up to be. Just go and read godlike for an hour and see what happens when people try and use intuition to explain everything.

There may be deeper understanding of the underlying mechanisms of QM, but I very much doubt the counter-intuitive results will be overturned- they're too accurate to be able to change much.

pixelator
2003-Jun-23, 09:43 PM
The weird mathmatical model the early astronomers had when they thought the earth was at the center was pretty accurate too, in calculating the positions of the planets and such. It was just very convoluted. I don't doubt the accuracy of QM, just wondering if some "grand unifying theory" will eventually be discovered and be much simpler.

on the same track: doesn't string theory somehow try to simplify QM? again, if I am showing my ignorance, forgive me.

CthulhuBob
2003-Jun-23, 10:02 PM
And now for a silly hypothesis from the peanut gallery:

They always say that ancient or backward cultures have insights into the wonders of Nature, and in some cases this is actually true :D . Now what if ancient cultures had an intuitive understanding of QM?

My example is sympathetic magic. For example, the voodoo doll is a form of Quantum Entanglement: after all when the Bokor pokes a pin into the crotch of a voodoo doll a man screams in agony 5 miles away instantly :) .

kilopi
2003-Jun-23, 11:46 PM
It kind of reminds be of the complex theories the old geocentric astronomers had to come up with to explain the planetary orbits, and then along comes Galileo and simplifies everything by putting the sun in the center instead of the earth.
Copernicus is usually given the credit for that.


Sadly, I do not think this is going to happen. The thing is, when you contemplate the maths, QM actually appears relatively simple (mathematically speaking). It's the results that are counter-intuitive.
Well, sure, but Newton's laws look relatively simple, but nobody has solved the three-body problem. And Newton's laws were overthrown by General Relativity.


Ironically, the other "great" 20th century physics counterpart to QM, General Relativity, is relatively complex mathematically (at least it appears to be to me) but its results are wonderfully intuitive (rubber sheets etc).
Again, it depends upon how you look at it. Just look at the equation on this webpage (http://www.aip.org/pt/nov99/wilczek.html), about a third of the way down, called "the central equation of general relativity theory." Looks pretty simple, no?


Intuition is not all it's cracked up to be.

Hmm...I suspect you're right.

djsmeg
2003-Jun-24, 01:34 AM
It kind of reminds be of the complex theories the old geocentric astronomers had to come up with to explain the planetary orbits, and then along comes Galileo and simplifies everything by putting the sun in the center instead of the earth.
Copernicus is usually given the credit for that.

Sadly, I do not think this is going to happen. The thing is, when you contemplate the maths, QM actually appears relatively simple (mathematically speaking). It's the results that are counter-intuitive.
Well, sure, but Newton's laws look relatively simple, but nobody has solved the three-body problem. And Newton's laws were overthrown by General Relativity.

You're right of course, Newton's equations can't be solved analytically when there are more than 2 variables. I think the same applies to Schrödinger's equation. But analytic insolubility does not necessarily imply complexity of the underlying rules (Newton's or Schrödinger's). They may indicate chaotic behaviour under the correct circumstances, but they are results of the system, a counter-intuitive result in itself: simple systems have complex results.



Ironically, the other "great" 20th century physics counterpart to QM, General Relativity, is relatively complex mathematically (at least it appears to be to me) but its results are wonderfully intuitive (rubber sheets etc).
Again, it depends upon how you look at it. Just look at the equation on this webpage (http://www.aip.org/pt/nov99/wilczek.html), about a third of the way down, called "the central equation of general relativity theory." Looks pretty simple, no?

Not seen that particular expression of GR before. I could never get my head around the Riemannian tensor expressions I got exposed to- but then I kind of got thrown in the deep end. *shiver*



Intuition is not all it's cracked up to be.

Hmm...I suspect you're right.
My intuition tells me I'm probably wrong :D

sarongsong
2003-Jun-24, 01:51 AM
There may be deeper understanding of the underlying mechanisms of QM, but I very much doubt the counter-intuitive
results will be overturned- they're too accurate to be able to change much.
Mmmh, can't help but wonder if maybe an alternate method of viewing the situation could help. This NYTimes article, "Savant For a Day", reports 40$ of the subjects display "improved or new mental powers" after undergoing frontal lobe magnetic pulsing [Transcranial Magnetic Pulsing=TMS], in a controlled laboratory environment.
http://www.nytimes.com/2003/06/22/magazine/22SAVANT.html
(free registration may be required to view article)

pixelator
2003-Jun-24, 03:11 AM
I don't think I want anyone pulsing my lobes :)

--
Sorry about forgetting about Copurnicus (sp?)

I think we are all in the matrix anyway so everything breaks down to 1's and 0's - pretty simple. :D :D

Archer17
2003-Jun-24, 03:51 AM
Quantum anything boggles my mind. I read somewhere that photons behave differently if they are observed, which is boggling enough but the magazine I read (wish I remembered which one it was, possibly Discover magazine) talked about the same effects from starlight many light-years away. I got the impression they were implying that the individual photons "knew" they would be observed by someone on Earth many years down the road. I read this a few months back. I might've misunderstood what the article was trying to say but it gave me a headache trying to figure it out.

snowcelt
2003-Jun-24, 01:18 PM
Quantum anything boggles my mind. I read somewhere that photons behave differently if they are observed, which is boggling enough but the magazine I read (wish I remembered which one it was, possibly Discover magazine) talked about the same effects from starlight many light-years away. I got the impression they were implying that the individual photons "knew" they would be observed by someone on Earth many years down the road. I read this a few months back. I might've misunderstood what the article was trying to say but it gave me a headache trying to figure it out.

Of course, what you just said seems to be counter-intuitive right? Hawking says that there is nothing wrong about looking at time as not being favoured to be exclusivily one-directional (Past to the future, intersected by the now), but, in fact being omni-directional.

Klausnh
2003-Jun-26, 12:52 AM
Quantum anything boggles my mind. I read somewhere that photons behave differently if they are observed, which is boggling enough but the magazine I read (wish I remembered which one it was, possibly Discover magazine) talked about the same effects from starlight many light-years away. I got the impression they were implying that the individual photons "knew" they would be observed by someone on Earth many years down the road. I read this a few months back. I might've misunderstood what the article was trying to say but it gave me a headache trying to figure it out.

Of course, what you just said seems to be counter-intuitive right? Hawking says that there is nothing wrong about looking at time as not being favoured to be exclusivily one-directional (Past to the future, intersected by the now), but, in fact being omni-directional.
I’m confused. In the space part of space-time, space does not flow and is not created. So if we speak of the time part of space-time, why do we assume that time flows and is being created? Isn’t time just another dimension? Aren’t we confusing the dimension of time with our perception of the flow of time?