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No, quantum entanglement does not allow you to communicate faster than light (flownet.com)
51 points by lisper on June 11, 2011 | hide | past | web | favorite | 25 comments



This article is extremely good. We always criticize pop-science journalism but in my mind, this is what good technology journalism looks like. I wish to hell that I could subscribe to a magazine like this instead of the hand-wavy baby talk that and sensationalism they are currently filled with.

I think it's a real shame that even scientists are often getting the baby-talk version of each-other's fields. Biologists, chemists, and astrophysicists should be able to read intelligent summaries of the findings in Quantum Mechanics without having to go to the journals.

The writing is challenging but the concepts themselves are challenging. Too often I think the scientists themselves try to summarize their work into a nice pull quote that sounds mysterious and interesting but they miss out on the opportunity to educate.


Thanks!


The wikipedia article about this goes more in depth http://en.wikipedia.org/wiki/No-communication_theorem


This appears to have previously been posted in a comment on http://news.ycombinator.com/item?id=2644349


I always knew there was something shady about the Illusive Man's tech.


You can communicate faster than light if you use a medium which travels faster than light, like graviton pulses which as far as I know travel infinitely fast.

All you have to do is take a black hole and figure out a way to rotate it at will. The gravity well imprint it leaves in space can be measured at a distance, thus sending a bit of data faster than light.

"You can't communicate faster than light" is about as true as "Men can't fly". It is only a matter of engineering.



tldr


The title says it all. Believe it.


Actually there are many experiments showing it does...

Yes, physics hasn't yet solved how that can work with Relativity, but if you are a scientist you should follow what experiments say, not what you believe.


Experiments that show that you can communicate faster than light using quantum entanglement?

The great misunderstanding about quantum entanglement is that while it seems like the two parties at the other ends can get the same information about the entangled system simultaneously, they can't actually push any information of their choosing through the system. Which makes it useless for communication.

Could you please point us at papers/experiments that show sending information through quantum-entangled particles? If that's true that would be a huge thing.


Why can't the sender of a message just turn his system on and off to represent 0s and 1s?


He can't. It doesn't work that way. I'm not sure what you think the reciever would be able to detect if the sender did that, but there's no detectable signal.

If you provide a more detailed picture of what you're envisaging then I can probably explain exactly what's wrong with it, but please read and understand

http://en.wikipedia.org/wiki/Bell_inequality

and

http://en.wikipedia.org/wiki/Bloch_sphere

along with any subordinate articles you'd need in order to understand these two, before proceeding.


The linked paper (which really is written for a layman), explains exactly that.


List experiments please. :)


I don't know anything about this, so yes I'm naive. But when I read this, I think about the Wright brothers. They were told something was impossible, and it was right up until they did it. So possible to communicate faster than light?? I have no idea, but I hope somebody keeps trying despite what the current accepted science says.


I don't know anything about this, so yes I'm naive. But when I read this, I think about the Wright brothers

Perhaps if you did know something about this you'd understand why this is an annoying sort of comment. Nothing personal, this kind of thing happens a lot.

General public: Hey scientists, is it possible to communicate faster than the speed of light?

Scientists: Gee, I dunno, let's go figure that out.

[many years of hard work]

Scientists: Whew, well we've gone away and done a lot of hard work and it turns out that it's impossible. Here's a twenty-page pamphlet with a few equations which summarises the most relevant points.

General public: Hummmph, well, I haven't bothered to read that pamphlet, but I can't help but think you're being closed-minded and that in fact it might be possible but you're just too dumb to figure it out. [goes back to watching Star Trek]

The most annoying thing about this line of argument is that it's impossible for the voice of conventional wisdom to actually win it. We can't prove that faster than light travel is impossible, nor that there isn't a dragon hiding in your garage (carefully hiding from every observation), nor the nonexistence of ghosts or body thetans.

If you want to start an argument with Every Physicist In The World about whether it's possible to send information faster than the speed of light, it's nice if you familiarize yourself with the arguments as to why it's impossible first. I think you might agree that it's less like the Wright Brothers and more like King Cnut.


The comparison isn't very good. Anyone telling the Wright brothers flight was impossible didn't have science on their side. All they had to do was look out a window and see a bird flying to know that. I suspect "that's a hard problem" morphed into "flight is impossible" over time because it makes their story more inspirational.


Also, there's a difference between "using quantum entanglement to communicate faster than light" and "communicating faster than light".

If I understand it correctly, it's theoretically feasible to achieve the the latter (in effect).

While it's impossible to send information at speeds that exceed c, it should be possible to bend the spacetime (e.g. using worm holes) so that the information would appear to have traveled faster than light.


While it's impossible to send information at speeds that exceed c, it should be possible to bend the spacetime (e.g. using worm holes) so that the information would appear to have traveled faster than light.

Wormholes, it should be noted, are "possible" in only a rather remote sense. If you put a wormhole into the equations of general relativity and say "Hey general relativity, is this a valid solution to your equations" it'll say "Uhhh, sure!". But then if you ask it how to arrange masses in order to actually get that solution it'll say "Haha, you can't do that."


Can you please expand on that last line? I read it two ways and I'm not sure which one you mean.

Does the "you can't do that" refer to getting a how-to-build-a-wormhole recipe from general relativity, i.e. "I can't tell you how to build one, go figure it out yourself".

Or is it more along the ways of "You don't have a worm hole? Well too bad, there's no way you can create one. But hey, it could totally hypothetically exist."

If it's 1) then we could possibly build one (or find it in the universe somewhere) and GR just doesn't tell us how. If it's 2) then we know it can't even be created.


I'm not an expert on wormholes, but: general relativity will tell you how space curves for any ol' distribution of mass you like, and it tells you there ain't no distribution of mass you can arrange that'll give you a wormhole.

On the other hand, we still don't understand the whole relativity/quantum-mechanics overlap region, so it's possible that whatever new physics are waiting for us in that regime just might include wormholes.

I'm really reluctant to say that, though. Many people seem to jump straight from that to drawing pictures of wormhole-hopping spaceships. Sorry, it's very very very very very very very unlikely to happen.


I didn't know that you couldn't arrange mass in any way to get a wormhole.

I've never been able to figure out in my (broken, I'm sure) mental model how you could create a wormhole but I suspected that the people who actually understood physics did know.

Thanks a lot, man. Interesting stuff.


There is a huge difference between something be "impossible" and something being theoretically impossible. The first is an engineering problem. The second is a much deeper level of problem.

The Wright brothers didn't have to overturn any accepted theoretical constructs to build the airplane. On the contrary, the theory at the time said they were on the right track. It was the general public that thought it was impossible.


There's a difference between a theoretical impossibility and a practical impossibility. The latter can be overcome by technological inventions; the first requires new theory. There hasn't really been any new fundamental theory in the last 70 years. Everything has been expansion, deepening, explication, detailing of what was already known, suspected, possible within the conceptual frameworks.




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