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Researchers quantum teleport particle of light six kilometres

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Re: Researchers quantum teleport particle of light six kilometres

#61

Post by socmag »

semi-extrinsic wrote: post #47
d_theorist wrote: post #36

I had thought that quantum entanglement could not be used for communication because the state that is transmitted is random, and cannot be controlled at either end. But, there are quotes in this article to the contrary. e.g.: “Such a network will enable secure communication without having to worry about eavesdropping, and allow distant quantum computers to connect,” says Tittel. Was my understanding mistaken?

I took a quantum optics course once. It's true what you say that entanglement can't be used to communicate (by itself), hence no problems with relativity, speed of light etc. This is known as the No-communication theorem: https://en.wikipedia.org/wiki/No-communication_theorem But together with a conventional communications channel (e.g. radio signals), you can use quantum entanglement to create a secure communication…

Right, "Did you get it?" doesn't need to confirm the information transferred

Re: Researchers quantum teleport particle of light six kilometres

#62

Post by lossolo »

nabla9 wrote: post #54
phkahler wrote: post #3

>> Researchers teleport particle of light six kilometres I'm sure they did nothing of the sort. At best they transferred an unknown state of a photon to another photon six kilometers away, then confirmed via measuring both.

Not so fast. There is a good reason to call it quantum teleportation and not quantum facsimile. When you move matter from one place to another it moves, it's not copied. When move classical information (or state) , you can retain the original or multiply it many times. Quantum teleport demonstrates interesing aspects of quantum information that makes it work like material thing. When information (quantum state) moves…

It does not work as material thing that is teleported. When you make measurement quantum function collapses and something that we don't know is happening and it's not teleporting anything because state is changed faster than speed of light, and no information or material can travel faster than that. This is a known paradox. Anton Zeilinger (father of quantum entanglement) is describing this in his books in more detail.

Re: Researchers quantum teleport particle of light six kilometres

#63

Post by aparent »

bbctol wrote: post #60
brazzledazzle wrote: post #42

Earlier quoted context omitted.

Is "measurement" or "observation" a simplified term for a complex process? It can't be as simple as a human "looking" at something since there's nothing special about humans (that I know of). I really wish I had the time and capability to understood how quantum entanglement really works. It seems a lot like magic if you take the layman explanations at face value.

To "observe" can mean any sort of interaction between the particle and a larger, connected physical system. To observe something, you have to have a physical interaction with it (it is hit by a photon of light which then hits your eyes, to use the most basic example) and so its quantum state decoheres into a particular state. Most scientists are fine with the idea that it doesn't matter if the larger physical system…

>seems for just a second like a normal, intuitive process that's just been obscured through poor explanation--then you learn a little more and realize it's far more bizarre than you'd imagined.

This is a great explanation of the process of learning about quantum mechanics.

A good test once you start to think you have figured things out is to check how your own conceptual model deals with Bell violations or experiments like: https://en.wikipedia.org/wiki/Quantum_eraser_experiment

Re: Researchers quantum teleport particle of light six kilometres

#64

Post by empath75 »

brazzledazzle wrote: post #42
jdmichal wrote: post #28

I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…

Is "measurement" or "observation" a simplified term for a complex process? It can't be as simple as a human "looking" at something since there's nothing special about humans (that I know of). I really wish I had the time and capability to understood how quantum entanglement really works. It seems a lot like magic if you take the layman explanations at face value.

Basically an observation is when an isolated particle becomes entangled with a larger system of particles (ie, a measurement device or person). At that point, it starts to behave more classically from the perspective of the system with which it is now entangled.

Re: Researchers quantum teleport particle of light six kilometres

#65

Post by wruza »

brazzledazzle wrote: post #42
jdmichal wrote: post #28

I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…

Is "measurement" or "observation" a simplified term for a complex process? It can't be as simple as a human "looking" at something since there's nothing special about humans (that I know of). I really wish I had the time and capability to understood how quantum entanglement really works. It seems a lot like magic if you take the layman explanations at face value.

More people-oriented answers: http://physics.stackexchange.com/questions/3158

Shortest answer to that question: http://physics.stackexchange.com/a/3162

>Imagine at home you put one glove in your coat without looking (and noticing it's only one of the two). After exiting the train you notice it's cold and you pull out that single glove. At this very instant you know it's either the left or the right glove, and you therefore know which one is left at home. However, no information was transmitted by your "measurement". Of course in quantum mechanics this is more complicated because of the not entirely measurable wave function, but this is the basic idea.

Re: Researchers quantum teleport particle of light six kilometres

#66

Post by nothrabannosir »

wruza wrote: post #65
brazzledazzle wrote: post #42

Earlier quoted context omitted.

Is "measurement" or "observation" a simplified term for a complex process? It can't be as simple as a human "looking" at something since there's nothing special about humans (that I know of). I really wish I had the time and capability to understood how quantum entanglement really works. It seems a lot like magic if you take the layman explanations at face value.

More people-oriented answers: http://physics.stackexchange.com/questions/3158 Shortest answer to that question: http://physics.stackexchange.com/a/3162 >Imagine at home you put one glove in your coat without looking (and noticing it's only one of the two). After exiting the train you notice it's cold and you pull out that single glove. At this very instant you know it's either the left or the right glove, and you the…

There are a lot of (justified) comments on that answer. A crucial point of quantum uncertainty is that it's different from classical intuition. Particles behave like waves (e.g. cause interference with themselves) until observed. That doesn't happen with the glove.

Re: Researchers quantum teleport particle of light six kilometres

#67

Post by empath75 »

phkahler wrote: post #3

>> Researchers teleport particle of light six kilometres I'm sure they did nothing of the sort. At best they transferred an unknown state of a photon to another photon six kilometers away, then confirmed via measuring both.

Particles do not have individual identity.

https://en.wikipedia.org/wiki/Identical_particles

Since there is always some degree of uncertainty w/r/t location and velocity, there's no way to tell which particle is which over time.

Re: Researchers quantum teleport particle of light six kilometres

#68

Post by skywhopper »

Not satisfied with asking me to subscribe to their newsletter before I've even read one article, this site _also_ popped up a request that I allow them to send me desktop notifications. Do people actually fill these things out? Why does ScienceBulletin think I might even want these things?

Re: Researchers quantum teleport particle of light six kilometres

#69

Post by marcosdumay »

asimuvPR wrote: post #14
wybiral wrote: post #9

Earlier quoted context omitted.

Until someone reads them and their meanings collapse. :)

At least we have a link that point to where this comment is at any time. ;-)

We just don't have any idea where the thread is going...

Re: Researchers quantum teleport particle of light six kilometres

#70

Post by empath75 »

Rooster61 wrote: post #5

The title of the article, while probably not intentional clickbait, is incorrect. Only the quantum state of the photon was "teleported", not the photon itself. The original photon was in fact destroyed, and only the information about its state was transmitted.

There is no way to distinguish photons from each other. If it has the same state as the original photon, it's the original photon.
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