High School How Could Quantum Communications Operate at Light Speed Given Relativity?

[darthgoon]

TL;DR

How would a quantum walkie-talkie work, if you took one of the radios onto the Starship Enterprise, at warp?

I feel like the emerging idea of quantum communications; is that you can exchange data via the synchronous states of entangled particles, across any distance, in real-time.
But, there's also this dilation in the physical world, at the speed of light, according to relativity.

So- how would the data exchange work between entangled particles, with one moving through space at the speed of light, relative to the other?

If there's a simple answer to this, i'll eat my hat.
I'm going to go buy a hat, sterilize and quarantine it for two weeks; and then eat it.

 

[PeterDonis]

The scenario you describe is inconsistent with the laws of physics, since particles of matter cannot move at the speed of light relative to each other. So it is pointless to ask what the laws of physics predict about it.

If there's a simple answer to this, i'll eat my hat.

The simple answer is above. Let us know how your hat tastes.

 

[PeterDonis]

I feel like the emerging idea of quantum communications; is that you can exchange data via the synchronous states of entangled particles, across any distance, in real-time.

Your feeling is incorrect. You cannot use quantum entanglement to exchange information faster than light.

 

[darthgoon]

Your feeling is incorrect. You cannot use quantum entanglement to exchange information faster than light.

And then i found this explanation- https://www.forbes.com/sites/chador...faster-than-light-communication/#517393603a1e

Which I guess, makes good enough sense to me, as a layman.

And i get the "compare notes" idea, in order to actually know if the data was actually a purposefully forced state. But that's the problem with radio, too.
So, what if you treat it like radio, you just play everything over the speaker, even if some of it is static. Couldn't you expect that some of it will be the audio you're trying to hear?

(I'm a village idiot/science nerd, thinking in very high-level ideas here)

 

[phinds]

So, what if you treat it like radio, you just play everything over the speaker, even if some of it is static.

ALL of it would be totally random "static". There is NO information content transmissible by entanglement.

 

[Dale]

So, what if you treat it like radio, you just play everything over the speaker, even if some of it is static.

But all of it is static. Since you have only static then you don’t have communication

 

[phinds]

@darthgoon what you seem to be not quite getting is that you can't modify a characteristic of one element of an entangled pair and so automatically make the other one of the pair take on the opposite characteristic. THAT is what you would have to be able to do to communicate via entangled pairs.

BUT ... all you can actually do is MEASURE one of elements and then know, because they are entangled, that what ever random value you got in that measurement, subsequent measurement of the other element will produce the opposite result. So what you get on BOTH ends is random values from each measurement, it's just that if you compare them later, you'll find that the characteristic of one element turned out to be the opposite of the other element. You can only find THAT out by sending information at no more than light speed, not faster.

 

[PeroK]

And then i found this explanation- https://www.forbes.com/sites/chador...faster-than-light-communication/#517393603a1e

Which I guess, makes good enough sense to me, as a layman.

And i get the "compare notes" idea, in order to actually know if the data was actually a purposefully forced state. But that's the problem with radio, too.
So, what if you treat it like radio, you just play everything over the speaker, even if some of it is static. Couldn't you expect that some of it will be the audio you're trying to hear?

(I'm a village idiot/science nerd, thinking in very high-level ideas here)

Here's a simple way to look at it:

Suppose you want to send your friend a message at a predetermined time using a pair of entangled particles.

Your code is: 1 = do something; 0 = do nothing.

You want your friend to do something (so you want to send him the message "1"). You go to your entangled particle and measure it. But, you get "1", so you know your friend will get "0". Bad luck! You just sent the wrong message - if we can put it like that. You know what data your friend will see, but it's not the data you wanted to send.

In measuring your particle you cannot control the outcome. You cannot control your friend's outcome, so you cannot send a message.

 

[Nugatory]

I feel like the emerging idea of quantum communications; is that you can exchange data via the synchronous states of entangled particles, across any distance, in real-time.

That’s not what quantum communications is about; as the posts above have explained, you can’t exchange data that way.

However there are other possible applications, and usually that’s what people mean when they talk about quantum communication. For example you and I could repeat the process @PeroK describes above one thousand times. When we’re done we both have a random string of one thousand ones and zeros so haven’t told each other anything yet... but we each know what the other’s string is by looking at our own. We can use these as encryption keys for messages that we send using ordinary methods. It’s not as exciting as faster-than-light communication, but if you’re trying to build a secure communication system it’s still pretty cool.

 

[darthgoon]

So I actually learned a lot about entanglement in this thread... I'm fixing to make a hat out of pancakes, and eat it. It's going to be chocolate chips... And delicious.

But you all seemed to zero in on the side note in my nonsensical question.

I'm not so much wondering if entanglement can specifically be used as a radio. I was using that as a reference for the idea that real-time communications across space, might exist. And how it would work at acceleration.

But I think I have an answer; in that, that style of communication cannot exist at acceleration in the first place.

 

[PeterDonis]

I was using that as a reference for the idea that real-time communications across space, might exist.

And what you've been told in this thread is that they don't. You can't communicate faster than light.

 

[PeterDonis]

that style of communication cannot exist at acceleration in the first place.

It also can't exist without acceleration. It can't exist, period.

 

[darthgoon]

It also can't exist without acceleration. It can't exist, period.

Ohhh... Never say never.

 

[PeterDonis]

Never say never.

Either you accept that our best current laws of physics are the only tool we currently have to answer your question, or you don't.

If you do, then we can say "never", since that's what our best current laws of physics say.

If you don't, then there's no point in asking the question in the first place, since if you're allowed to say things can violate our best current understanding of the laws of physics, we have no basis for answering your question at all.

 

[darthgoon]

If you don't, then there's no point in asking the question in the first place, since if you're allowed to say things can violate our best current understanding of the laws of physics, we have no basis for answering your question at all.

I think there's good reason to ask the question anyway. Because, how could you ever get where you want to go, without first knowing where you are?

"Either you accept you're going to fall of the edge of the earth, if you sail that far, or you don't..."
Was probably once a sentence someone else once said too.

 

[weirdoguy]

"Either you accept you're going to fall of the edge of the earth, if you sail that far, or you don't..."
Was probably once a sentence someone else once said too.

So you're comparing totally non-scientific belief with physics based on thousands of experiments? It's not a good strategy if you really wan't to learn something.

 

[darthgoon]

So you're comparing totally non-scientific belief with physics based on thousands of experiments?

No, I'm making an analogy to other definitive statements, in history, that would exemplify the short-sightedness of any sort of ultimatum of a statement.

I don't disagree with any of the physics in this thread. I think if anyone took the time to read it, that would be obvious.

Homeboy up above, seems to want to stomp on his keyboard to disagree with me, for the sake of disagreeing with someone that he thinks he can call stupid. You're starting to look a lot like him, right now, too...

 

[darthgoon]

If you can't take my pre-descriptively nonsensical question with as much seriousness as it deserves, and respond in kind, on topic...
Stay off my thread.

 

[weirdoguy]

No, I'm making an analogy to other definitive statements, in history,

And in that analogy you compare totally non-scientific belief with physics based on thousands of experiments.

Homeboy up above, seems to want to stomp on his keyboard to disagree with me, for the sake of disagreeing with someone that he thinks he can call stupid.

No, he just kindly tells you how exactly science works. You came here to learn, didn't you? If yes then you should know that when you say something that is not true then you will be corrected. In science, if you ask a question then you have to have the basis on which you can answer this question. Here this basis is physics and physics says (based on thousands of experiments) that there is no faster than light communication. If you dismiss physics then you are left with nothing. And you can't answer your question based on nothing.

If you can't take my pre-descriptively nonsensical question with as much seriousness as it deserves, and respond in kind, on topic...

If you can't take answers from experts like PeterDonis, with as much seriousness as they deserve...

 

[PeterDonis]

I think there's good reason to ask the question anyway.

Asking the question is one thing. Ignoring the answers you get is another. You are doing the latter.

Thread closed.