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Entanglement and communication
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olePigeon
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Nov 10, 2010, 07:15 PM
 
Everyday Entanglement - Science News

Pretty cool story on breakthrough experiments with quantum entanglement (spooky action.) One of the experiments is really exciting when two physicists transmitted an entangled photon across normal phone lines.

If you have entanglement of two particles or catlike structure, when one changes, the other entangled object instantly changes as well.

You could have a modem of some type that negotiates by sending out an entangled photon over your phone line (or satellite) to a server anywhere in the world, where the server would store and monitor the entangled photon. Now when your computer changes the state of the photon (say, as positive spin or negative negative spin for 0 or 1) the server would instantly see those changes as well. Zero latency no matter where in the universe you are.

Other really cool experiments are exploring dynamically creating entanglement, dissolving it, then recreating it at a later time. This would allow you to make unbreakable encryption. You would have a single qubit in a random state, impossible to predict and impossible to guess, until you bring a "key" that entangles with the qubit, unlocking the encryption. It would be 100% secure unless you can break the known laws of physics somehow... in which case you'd probably win a Nobel prize in physics anyway.
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Doc HM
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Nov 10, 2010, 07:53 PM
 
I thought entanglement only worked because it did not violate causality (or the light speed issue, hence spooky action) because while it is certainly possible for an object to travel faster than the speed of light (or even infinitely fast, it is not possible to use this to transmit any information. (given scientists rather broad definition of information in this case).
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olePigeon  (op)
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Nov 10, 2010, 08:14 PM
 
Oh shucks, you're right. I thought there was a whole new cool experiment.

While the entanglement is instantaneous, the information required to construct the second photon must still be transmitted over traditional means.

Still, this could mean completely secure communications. You could create a packet system around entangled photons, ensuring the information arrives at its destination exactly how you sent it.


Maybe they'll find some loophole for transmitting information that way. Not faster than light, but a way to "cheat" by abusing space-time to make shortcuts.
"…I contend that we are both atheists. I just believe in one fewer god than
you do. When you understand why you dismiss all the other possible gods,
you will understand why I dismiss yours." - Stephen F. Roberts
     
Doc HM
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Nov 11, 2010, 06:34 PM
 
Originally Posted by olePigeon View Post
Maybe they'll find some loophole for transmitting information that way. Not faster than light, but a way to "cheat" by abusing space-time to make shortcuts.
Maybe they will: Science: Light Pulse faster than Light
Experiments in making light move faster than light.
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Oneota
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Nov 11, 2010, 08:09 PM
 
So is this the same thing as ansibles and philotes?
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olePigeon  (op)
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Nov 11, 2010, 08:16 PM
 
Originally Posted by Doc HM View Post
Maybe they will: Science: Light Pulse faster than Light
Experiments in making light move faster than light.
Yeah, but it requires sending it along a beam of light moving at c, so you still can't send information faster than light.

It's funny because after you measure it, you can find waves that happen before you sent the pulse; effect preceding cause.
"…I contend that we are both atheists. I just believe in one fewer god than
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olePigeon  (op)
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Nov 11, 2010, 08:25 PM
 
Originally Posted by Oneota View Post
So is this the same thing as ansibles and philotes?
If they could actually transmit information, it'd be an Ansible. I guess strings would be Philotes, but String Theory is the Intelligent Design of particle physics. The LHC is going to be testing some of the conjecture behind string theory. It's already created quark-gluon plasma, which hasn't been seen since the initial big bang.

No Higgs boson so far, but all the data is being studied, so we don't know yet. They do believe they found a new quark, though.
"…I contend that we are both atheists. I just believe in one fewer god than
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Oneota
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Nov 11, 2010, 08:52 PM
 
Originally Posted by olePigeon View Post
If they could actually transmit information, it'd be an Ansible. I guess strings would be Philotes, but String Theory is the Intelligent Design of particle physics. The LHC is going to be testing some of the conjecture behind string theory. It's already created quark-gluon plasma, which hasn't been seen since the initial big bang.

No Higgs boson so far, but all the data is being studied, so we don't know yet. They do believe they found a new quark, though.
I guess I don't understand the physics well enough to know why it couldn't be used to transmit information. Aren't they saying that if one of the entangled photons changes, its mate also changes instantaneously, regardless of where it is? Couldn't that be pretty easily harnessed to encode binary communications, at a minimum (and, depending on how many states these photons can be changed into, possibly beyond binary)?
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olePigeon  (op)
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Nov 11, 2010, 09:35 PM
 
Originally Posted by Oneota View Post
I guess I don't understand the physics well enough to know why it couldn't be used to transmit information. Aren't they saying that if one of the entangled photons changes, its mate also changes instantaneously, regardless of where it is? Couldn't that be pretty easily harnessed to encode binary communications, at a minimum (and, depending on how many states these photons can be changed into, possibly beyond binary)?
We don't have a device that can remotely observe two particles simultaneously and report back instantly. At any point when you measure one photon, you break entanglement. If Bob has X photon entangled with Mary's Z photon, how does Mary tell Bob that it changed? Is it correct? Is it wrong? As far as the information is considered, until Mary verifies with Bob, there's no way to tell what position the photon is in. Mary can't use entanglement to tell Bob because then Bob runs into the same problem.

Basically, you'd need to use quantum entanglement to report on the results of the first entangled photons without violating the laws of physics... a report that would in itself need to be observed and reported on instantly, of which the results of that report would need to be observed and reported instantly, et cetera, et cetera for infinity.

IF you could send the information instantly, that would mean it's faster than light. If Mary simply moved toward Bob's photon, she could observe the results before Bob even sent it! It'd violate causality.

Effect proceeding cause can be observed, but only in special circumstances like sending a pulse in a beam of light, and it doesn't really violate causality. Imagine of a beam of light like one of those horizontal escalator conveyer belt things at an airport... then stick it on a truck moving 60 Mph. Now you have a letter you wanna give someone that's at the end of the road 10 miles away. You could run down that conveyer belt, technically going faster than 60 Mph, but the truck will always be going 60 Mph, and it'll still take 10 minutes to get to the person to deliver your letter. Just because you're running down the conveyer belt doesn't mean the truck will get there any faster. Your letter will get to that person when the truck gets there in 10 minutes, no faster, no matter how fast you run up and down that conveyer belt.
"…I contend that we are both atheists. I just believe in one fewer god than
you do. When you understand why you dismiss all the other possible gods,
you will understand why I dismiss yours." - Stephen F. Roberts
     
Rev-O
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Nov 13, 2010, 01:37 PM
 
Originally Posted by olePigeon View Post
String Theory is the Intelligent Design of particle physics.
that line cracked me up! Of course Michio Kaku swears up and down that string theory, ahem, M Theory, is provable and has predictive quality. And what more evidence do you need than the word of a media savvy attention whore of a physicist that believes aliens have been visiting us?
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