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Why quantum entanglement doesn't allow faster-than-light communication (2016)

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Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#61

Post by elcritch »

yetihehe wrote: post #57
mrkeen wrote: post #56

Earlier quoted context omitted.

This is the simplest explanation, but it's also the null hypothesis. I believe that "nothing changes over there" implies not only no spooky action, but also no entanglement.

This is about word used for description of that thing. Just using entanglement is ok, but using "action" suggests that something changes. Words have some meaning and incorrect usage causes misunderstandings.

> Action implies something changes (there is a state called "before" and state called "after"). But nothing changes "over there", we just now know what actually happened (there is no state called "before" or it's value is "unknown", only state called "after").

> using "action" suggests that something changes

By my understanding, the delayed part is important. It implies something did change as the state of the earlier entanglement will be different based on a measurement which occurs after the entangled state has been created. If this is correct, then there has been an "action" at a distance.

Though an alternative understanding could be that the state is set based on a future event which hasn't occurred yet. That would avoid needing an "action" to change the state after the entanglement event, but implies other things.

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#62

Post by nobodyandproud »

Filligree wrote: post #43
stephc_int13 wrote: post #33

Most people don't understand enough about the fundamental properties of modern Physics. What we usually call the speed of light is in fact the maximum speed of information propagation. It is not about light, and you should think about quantum entanglement as a hidden variable, there is no magic there.

I was under the impression that local hidden variable theories had been disproven? It could be nonlocal of course, but that would imply information moving faster than light again. Unless you count the entirety of MWI as "hidden variables", I guess?

Non-Locality doesn’t mean information travels faster than c.

The main article attempts to explain why instantaneous “spooky action at a distance” is real, yet information can’t be relayed this way.

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#63

Post by yetihehe »

elcritch wrote: post #61
yetihehe wrote: post #57

Earlier quoted context omitted.

This is about word used for description of that thing. Just using entanglement is ok, but using "action" suggests that something changes. Words have some meaning and incorrect usage causes misunderstandings.

> Action implies something changes (there is a state called "before" and state called "after"). But nothing changes "over there", we just now know what actually happened (there is no state called "before" or it's value is "unknown", only state called "after"). > using "action" suggests that something changes By my understanding, the delayed part is important. It implies something did change as the state of the earlie…

I suggest using "spooky correlation" to better explain this. It's just a forced correlation of two parameters after all. To make entanglement, we make an experiment where we force system to behave in a way that correlates results of two parameters. When we measure one, we know the other is correlated in a way that was set in our experiment. "Spooky" because it can hold at vast distances and across time.

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#64

Post by addaon »

amingilani wrote: post #4
TheDudeMan wrote: post #2

"3 Body Problem" has so many problems! Wake me up when the next "Expanse"-level sci-fi lands.

To expand on this, it uses quantum entanglement for FTL communication over a distance of 4 light years. Still a great story, though.

> To expand on this, it uses quantum entanglement for FTL communication over a distance of 4 light years. Still a great story, though.

Although I read the book when it first came out, I have basically zero memory of it, so I don't recall if FTL communication is essential to the story. However, having just watched the first season of the Netflix season, I explicitly noticed that even though it mentions use of FTL communication, the story absolutely doesn't need it at any time. There's a local representative of the distant folk who is clearly trusted to make decisions, and could represent the distant folk for all communication purposes.

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#65

Post by azulster »

causi wrote: post #35
endisneigh wrote: post #16

Earlier quoted context omitted.

What’s stupid about it?

It's dumb on two levels. Firstly, for a planet to evolve sapient life it must be inhabitable for, at minimum, millions of years if not billions, therefore if this orbital instability was going to wipe out the trisolarans it would've done it already. Secondly, the trisolarans are hyper-advanced. They turn individual protons into sapient robots and play with antimatter, therefore they can make a damn air conditioner. M…

broad strokes yes, you are right.

however you missed some explanatory details:

!!!SPOILERS BELOW!!!

the trisolarans specifically evolved to survive their chaotic orbit, by being able to completely "dry out" and wait in stasis for a safer time. this is based on how some worms and bacteria on earth have the ability to survive extreme conditions by similar protective stasis methods.

the trisolarans are very intelligent but their advancements are constrained by the need to rebuild the civilization at unpredictable intervals. this actually drives their technological innovation as they are existentially motivated to figure out how to predict the orbital intervals.

its also implied that the trisolarans did not think themselves very far advanced compared to humans, only that they had a few centuries head start on understanding the fundamental nature of physics. they conclude that all they need to do is sabotage our particle colliders to confound our ability to gain any more insight into subatomic mechanics to prevent us from achieving what they have

moving their civilization across interstellar space is far less difficult than it would be for humans mostly because the civilizations can be dehydrated and kept in storage, not needing supplies to live out the years in transit. even so it still takes incredible engineering and resource investment to achieve because the fleet must move semi-autonomously and reliably for centuries because FTL travel is beyond their ability.

it would be impossible to stabilize their orbit because the planet is being chaotically thrown between 3 large stars. they are also not just concerend with surviving the next "hot cycle" they had predicted true apocalypse for even their survivable species. IIRC the planet was doomed to eventually fall into one of the stars based on their predictions

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#66

Post by cwmma »

mrkeen wrote: post #3

The gap I still have in my understanding: One hypothesis is that there is no spooky action. One particle was 'always' going to resolve one way, likewise with the other. Like inspecting 'heads' on one side of a coin 'forces' 'tails' onto the other side. I accept that this coin-hypothesis has been disproved by people who actually know what they're talking about. But to me, this implies that you should build your spooky…

You can not tell whether a particle was measured or not by looking at its entangled pair.

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#67

Post by taeric »

magicalhippo wrote: post #14
honeyed_coffee wrote: post #9

Earlier quoted context omitted.

The spooky part occurs when two parties who share this entangled state know what measurement to perform. If the measurement choice aligns for both parties, their outcomes can be correlated precisely. If the measurement choices are not aligned, the outcomes are also random

> If the measurement choices are not aligned, the outcomes are also random Just to be a bit pedantic, as it can otherwise lead to some confusion: the measurement outcomes are always random. If the particles are entangled, then it is the correlations that are not random.

This is still a part that annoys me. I have asked why you can't use the correlations to facilitate communication, and people always seem to think I'm asking why you can't do this per particle. I get that the the individual measures are basically useless on their own. Question is if the correlations can be confirmed so well, why can't that be used?

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#68

Post by cwmma »

stephc_int13 wrote: post #33

Most people don't understand enough about the fundamental properties of modern Physics. What we usually call the speed of light is in fact the maximum speed of information propagation. It is not about light, and you should think about quantum entanglement as a hidden variable, there is no magic there.

But isn't that the frustrating thing about this, it implies superluminal communications just in a non-useful way. Managing to make the speed of light not be the maximum speed of information propagation but only in a technical and useless way.

Re: Why quantum entanglement doesn't allow faster-than-light communication (2016)

#70

Post by plagiarist »

Workaccount2 wrote: post #27
mrkeen wrote: post #3

The gap I still have in my understanding: One hypothesis is that there is no spooky action. One particle was 'always' going to resolve one way, likewise with the other. Like inspecting 'heads' on one side of a coin 'forces' 'tails' onto the other side. I accept that this coin-hypothesis has been disproved by people who actually know what they're talking about. But to me, this implies that you should build your spooky…

You cannot tell if a particle has been measured or not without...measuring it. The key to understanding this is that _any_ interaction with anything counts as a "measurement" from the particles perspective. I like to think that our simulation has a bandwidth compression algorithm that only decodes the state of a particle when it needs to calculate an interaction. Just like how your dungeon crawler doesn't spawn mobs…

I've had a similar head canon that Planck lengths are the simulation's floating point epsilon.
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