Quantum Teleportation Achieved Over 16 km In China

Laxori666 writes "Scientists in China have succeeded in teleporting information between photons farther than ever before. They transported quantum information over a free space distance of 16 km (10 miles), much farther than the few hundred meters previously achieved, which brings us closer to transmitting information over long distances without the need for a traditional signal."

Comments

Lightspeed limited, not an ansible

[Anonymous Coward]

Before you think this is awesome, this is not an ansible, information is transmitted at lightspeed only.

Re:Lightspeed limited, not an ansible

[PinkyGigglebrain]

This raises a question that has been on my mind for awhile. I hope I can explain this but I'm not an expert in physics so bear with me.

Also, please do not just say "Your wrong, GTR says that can't happen", you would be "citing authority" and it really kills the validity of your rebuttal. Sort of like saying "God exists because the Bible says so". Please explain WHY its wrong, as in cite what portion of GTR says it can't happen so I can read it and see where how I went wrong.

According to General Theory or Relativity, as defined in the link you posted, if a mass were to suddenly appear at a location in space-time, say in the forward Lagrange point of Jupiter's orbit, it would take X amount of time before the gravity from that mass would affect the orbits of the other planets in the Solar system. X being equal to time it would take for light to travel from the location of the mass to the rest of the planets in the Solar system.

Have I got it right so far?

But my understanding is that, according to GTR, gravity is caused by the deformation of space-time by a mass. So the mass that suddenly appeared would deform space-time around it, thus imposing a gravitational influence on all objects in range.

Here is what has me going "wait, what?"

Also according to GTR space-time can expand/contract at speeds greater than that of c in a vacuum, as described in the "inflation" theory of the early universe and Alcubierre's "warp drive" theory. Since the mass deforms space by "stretching" it wouldn't that mean that the influence of a mass could affect an object at a distance in less time than it would take light to travel that same distance? Since the "fabric" of space-time could alter faster than light can travel across it.

I'm hoping to get some insight into how I could be wrong, because based on what I know I can't see any reason why it can't happen. It could explain why we haven't detected gravity waves using interferometry, if the gravity wave, a distortion of space-time was moving faster than light it wouldn't be able to affect the phase of the light beams.

Thank you in advance to those who actually provide some useful info to help me improve my understanding.

Re:Progress..

[Pharmboy]

And once they get to an economic level that is closer to what the rest of us enjoy in the Western world, they will start caring. When you are hungry, you only want bread. When you are homeless, you only want shelter. When you have plenty to eat and a decent place to live, you want freedom.

Re:Obligatory

[jo_ham]

Dare I say, if you don't find xkcd funny, the material might be somewhat... not aimed at you.

To be delicate.

Especially if you don't find *any* of them funny (although not all of them are designed to be humourous).

Peer Reviewed

[areusche]

http://science.slashdot.org/story/10/04/19/0132246/Chinas-Research-Ambitions-Hurt-By-Faked-Results

This story alone makes me skeptical about any major scientific breakthroughs until someone can peer review the results.

Congrats to the hardworking people on the project, however I will be applauding their work with less skepticism when I hear that MIT, Cornell, CMU, etc confirm the results.

Re:Wait, does this mean...

[buanzo]

Actually... http://en.wikipedia.org/wiki/Photons#Experimental_checks_on_photon_mass they're still not sure :P

Re:Wait, does this mean...

[lgw]

There is no "quantum shit going on" that breaks special relativity. Attention world: Once and for all, quantum theory does not break relativity.

How right you are, and I have an elegant theory of quantum gravity that reconciles quantum mechanics with general relativity. Unfortunately, my proof is too large to fit in this forum post.

Re:This would be interesting for production use...

[Pfhorrest]

Except it's not quite like that.

You and Alice put two shirts in a bag, shake it up, close your eyes, and you each pull out a magic mixed-up shirt which cycles through the color spectrum at random varying speeds (but the same speed on each shirt) until you look at it, at which point it stops cycling on one particular color, and the other stops cycling on the complementary color. You put your shirts in your respective briefcases and go on your trips, and when you get there, you open your briefcase and see your shirt has stopped on red. So now you know that if Alice looks in her briefcase, she will see her shirt has stopped on cyan.

However, the question is again, "so what?"

You don't get to decide whether the shirt is red or blue when you look at it (since the speed it cycles at varies randomly, so you can't very well time it or something), so it's not like you can send a "cyan" to Alice for a "0" and a "red" for a "1". Likewise, when Alice opens her briefcase and sees a cyan shirt, she doesn't even know if you have looked at your shirt or not yet; her shirt might have stopped flashing and just landed on "cyan" by chance when she looked at it (making your shirt stop at "red"), or you may have looked at your shirt and seen "red", making her shirt stop right then too on "cyan".

The only thing that's interesting about these synchronized flashing shirts is the fact that when one stops cycling the other stops at EXACTLY the same time no matter how far away they are. We only know this because when you and Alice do this over and over again and then compare your notes afterward, you always find out that your shirt stopped on one color and hers on the complement. That's interesting because if there was any time delay between one stopping and the other, you would expect the hue-difference between the two shirts to vary with distance: at close distances you'd get close to complimentary colors because they stop at close to the same time, while at larger distances the second shirt would stop slightly later making it slightly off from complementary. And of course if there was no communication between them at all, there would be no correlation between what color you see and what color she sees. But you always see red when Alice sees cyan, and you always see yellow when she sees blue, and you always see green when she sees magenta. Which indicates that anybody looking at either shirt not only stops that shirt but also the other shirt instantaneously.

Which isn't of any practical utility, however, for the reasons described two paragraphs above. But it sure as hell is weird, isn't it?