Why quantum entanglement doesn't allow faster-than-light communication (2016) • Hacker News Board

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

#41

Post by endisneigh » Thu, Mar 28, 2024, 1:38 PM UTC

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…

> 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.

This is not a fact to begin with, and in the book their civilization was repeatedly wiped out.

> 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. Manufacturing habitats to isolate them from the effects of their orbit would be easier than almost every single other thing they do in the entire series, including transporting their whole species across interstellar distances. Some of the things they do would be harder than keeping their planet in a stable orbit by force.

This is not the failure mode they’re concerned with.

You also seem to drastically overestimate their capabilities.

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

#42

Post by gosub100 » Thu, Mar 28, 2024, 1:42 PM UTC

elcritch wrote: post #11

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…

> 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. The quantum erasure experiment is to my mind the best example of the spooky action at a distanc…

Delayed-choice blew my mind at first, but then learning that light-speed particles experience length contraction kind of debunks the "they traveled backwards in time" interpretation, at least from the photons perspective. They traveled 0 distance.

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

#43

Post by Filligree » Thu, Mar 28, 2024, 1:44 PM UTC

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?

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

#44

Post by Filligree » Thu, Mar 28, 2024, 1:48 PM UTC

gosub100 wrote: post #42

elcritch wrote: post #11

Earlier quoted context omitted.

> 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. The quantum erasure experiment is to my mind the best example of the spooky action at a distanc…

Delayed-choice blew my mind at first, but then learning that light-speed particles experience length contraction kind of debunks the "they traveled backwards in time" interpretation, at least from the photons perspective. They traveled 0 distance.

Photons don't travel at all, yeah, in a literal sense. It's still useful to measure travel length in 3-space, but that's more an analogy than a real event.

In four-dimensional space-time they 'travel' along a 0-length path; the correct formulation of Pythagoras' formula becomes "distance = t^2 - x^2 - y^2 - z^2".

Which would be an imaginary number for a spacelike path, yes, e.g. from one side of your table to the other. It's a useful imaginary number -- we call it 'length' -- but it doesn't correspond to a path that actually exists.

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

#45

Post by roywiggins » Thu, Mar 28, 2024, 1:49 PM UTC

youlweb wrote: post #29

Can we simply tell that the entanglement was collapsed on the other end? That would be sufficient to transmit information. If planet x is habitable when I get there, I measure/collapse this specific particle, whose counterpart is back on earth in a detector named "habitable". When the detector fires on earth because this particle was measured/collapsed on planet x, people on earth know planet x is habitable. There's…

This doesn't work, but if it did, you could use it to front-run stock market movements. No need to go to space to find an application.

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

#46

Post by gaze » Thu, Mar 28, 2024, 1:49 PM UTC

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’t tell if a particle has been measured or not.

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

#47

Post by slfnflctd » Thu, Mar 28, 2024, 1:49 PM UTC

mrkeen wrote: post #40

Workaccount2 wrote: post #27

Earlier quoted context omitted.

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 don't dispute this, but it's indistinguishable from the 'no spooky action' hypothesis. I can invent a story that the coin in my pocket has two sides, each of which is in a superposition of heads and tails. If you disprove that by repeatedly looking at both sides and noting that they always end up different, then I can invent the story that the observed side tells the unobserved side what to become. If you disprove…

I've never quite grasped this stuff to my satisfaction, and I strongly suspect part of why is because of some really bad popular examples (metaphors, allegories, thought experiments, whatever) which contain factually or logically incorrect language.

This comment chain is a prime example of the ways quantum mechanics are (mis)understood and how many of us struggle to fully reason out the implications of each piece of it. I hope we can all learn something.

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

#48

Post by gaze » Thu, Mar 28, 2024, 1:49 PM UTC

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…

No, you can’t tell if a particle has been measured or not _period_, without many identical copies of the same state and repeating the experiment many times.

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

#49

Post by [deleted] » Thu, Mar 28, 2024, 1:50 PM UTC

youlweb wrote: post #29

Can we simply tell that the entanglement was collapsed on the other end? That would be sufficient to transmit information. If planet x is habitable when I get there, I measure/collapse this specific particle, whose counterpart is back on earth in a detector named "habitable". When the detector fires on earth because this particle was measured/collapsed on planet x, people on earth know planet x is habitable. There's…

[deleted]

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

#50

Post by gaze » Thu, Mar 28, 2024, 1:52 PM UTC

cwillu wrote: post #36

youlweb wrote: post #29

Can we simply tell that the entanglement was collapsed on the other end? That would be sufficient to transmit information. If planet x is habitable when I get there, I measure/collapse this specific particle, whose counterpart is back on earth in a detector named "habitable". When the detector fires on earth because this particle was measured/collapsed on planet x, people on earth know planet x is habitable. There's…

Any time you feel tempted to treat collapse as an objective state of a single particle, remember that the collapse interpretation is mathematically indistinguishable from the multiverse interpretation. There's no test for whether collapse has happened other than measuring at both ends and comparing notes… and noticing that nature appears to be cheating somehow.

You can’t tell AT ALL if there was entanglement with one trial. You need to prepare the same state many many times and compare correlations many many times to establish correlations to within some error bound.