Curious about an idea of a modified polariser to send signals with QE

[tade]

So I'm curious about an idea of using a specially modified polariser to send signals with quantum entanglement, curious to know what's more there is to learn about the idea, for better or worse, its possibilities or impossibilities.

Ok so like in the Bell tests, measuring the spin of an elementary particle, and it has being likened to a coin flip, a 50/50 on either side, heads or tails.

But say we have a specially modified or fabricated polariser which can nudge the measurement results from 50/50 either way to 52/48. As the special polariser has been materially fabricated and synthesized with an anisotropic bias at the molecular level.

And then we are conducting Bell tests, with Alice and Bob monitoring the results at their respective ends. And then if Alice were to swap her polariser from a normal standard one to the special anisotropic one, Bob might be able to tell that she has done so, hence it being a form of signalling.

And I think that a 52/48 shift might be pretty interesting, it can be kinda small or really large depending on the angle you're viewing it from (and using "angle" in a metaphorical sense and not in literal physical one lol)

So I'm just curious and wondering about this idea, and also interested to know if it has been explored before.

 

[DrChinese]

So I'm curious about an idea of using a specially modified polariser to send signals with quantum entanglement, curious to know what's more there is to learn about the idea, for better or worse, its possibilities or impossibilities.

Ok so like in the Bell tests, measuring the spin of an elementary particle, and it has being likened to a coin flip, a 50/50 on either side, heads or tails.

But say we have a specially modified or fabricated polariser which can nudge the measurement results from 50/50 either way to 52/48. As the special polariser has been materially fabricated and synthesized with an anisotropic bias at the molecular level.

And then we are conducting Bell tests, with Alice and Bob monitoring the results at their respective ends. And then if Alice were to swap her polariser from a normal standard one to the special anisotropic one, Bob might be able to tell that she has done so, hence it being a form of signalling.

And I think that a 52/48 shift might be pretty interesting, it can be kinda small or really large depending on the angle you're viewing it from (and using "angle" in a metaphorical sense and not in literal physical one lol)

All Bob ever sees is a mixture of random outcomes, regardless of what Alice does. Kinda hard to send a message with that.

And yes, you can fashion a setup where there is a bias as you imagine. But that doesn't make any difference. The correlations come only when you compare Alice AND Bob's results. Which requires standard signaling (limited by light speed of course).

 

[tade]

All Bob ever sees is a mixture of random outcomes, regardless of what Alice does. Kinda hard to send a message with that.

And yes, you can fashion a setup where there is a bias as you imagine. But that doesn't make any difference. The correlations come only when you compare Alice AND Bob's results. Which requires standard signaling (limited by light speed of course).

oh interesting, though, I think that I'm not looking at any correlations, but just Bob observing some changes only from his own end, changes brought about by Alice swapping the polarisers.

 

[PeterDonis]

Bob observing some changes only from his own end, changes brought about by Alice swapping the polarisers

Bob cannot observe any change at his end based on Alice making changes at her end. He just sees random outcomes regardless. The only way for Bob to know that Alice has made a change at her end is for Alice to send a signal (at no greater than the speed of light) to tell him.

 

[tade]

Bob cannot observe any change at his end based on Alice making changes at her end. He just sees random outcomes regardless. The only way for Bob to know that Alice has made a change at her end is for Alice to send a signal (at no greater than the speed of light) to tell him.

so why doesn't swapping the polarisers lead to a change in the random outcomes

 

[DrChinese]

oh interesting, though, I think that I'm not looking at any correlations, but just Bob observing some changes only from his own end, changes brought about by Alice swapping the polarisers.

Alice sees:
HTTHHTTHHTT

Bob sees:
HTTHHTTHHTT

If Alice changes her polarizer (or doesn't even have one at all!), it doesn't affect Bob's results (as far as can be anyone knows) because they are RANDOM. All Bob ever sees is a random mix of H and T (or 0/1 or U/D or whatever). While you may not care about the correlations, that is what entanglement gives you: a precise estimate of Alice/Bob correlations.

 

[tade]

Alice sees:
HTTHHTTHHTT

Bob sees:
HTTHHTTHHTT

If Alice changes her polarizer (or doesn't even have one at all!), it doesn't affect Bob's results (as far as can be anyone knows) because they are RANDOM. All Bob ever sees is a random mix of H and T (or 0/1 or U/D or whatever). While you may not care about the correlations, that is what entanglement gives you: a precise estimate of Alice/Bob correlations.

though I was thinking that Bob's end might change from 50/50 to 52/48

 

[PeterDonis]

why doesn't swapping the polarisers lead to a change in the random outcomes

Because they are random, and random outcomes can't be controlled.

though I was thinking that Bob's end might change from 50/50 to 52/48

No. Bob's ratio of random outcomes only depends on the setting of Bob's polarizer, not on the setting of Alice's.

 

[tade]

No. Bob's ratio of random outcomes only depends on the setting of Bob's polarizer, not on the setting of Alice's.

hmm how about say Bob's photons being in entangled correlations with what Alice is doing, her polariser swapping

 

[PeterDonis]

how about say Bob's photon being in an entangled correlation with what Alice does

If you want to talk about that (very different) scenario, you will need to figure out how to entangle Bob's photon with "what Alice does" and then describe such a scenario so it can be analyzed.

 

[tade]

If you want to talk about that (very different) scenario, you will need to figure out how to entangle Bob's photon with "what Alice does" and then describe such a scenario so it can be analyzed.

so I imagine that the photons are entangled as per usual, though when it comes to the measurements, Alice has the available option to midway-through swap to the special polariser type, which as mentioned earlier, I'm wondering about the possibilities of the scheme, perhaps such as the possibility of creating such a polariser, and of it not breaking the entanglement

 

[PeterDonis]

so I imagine that the photons are entangled as per usual, though when it comes to the measurements, Alice has the available option to midway-through swap to the special polariser type, which as mentioned earlier, I'm wondering about the possibilities of the scheme, perhaps such as the possibility of creating such a polariser, and of it not breaking the entanglement

This just looks like the same scenario you posed in the OP, which has already been answered.

 

[tade]

This just looks like the same scenario you posed in the OP, which has already been answered.

hmm, seems like we're stuck in a comments loop

 

[tade]

This just looks like the same scenario you posed in the OP, which has already been answered.

hmm, seems like we're stuck in a comments loop

as i have replied to every single reply so far

 

[PeterDonis]

hmm, seems like we're stuck in a comments loop

as i have replied to every single reply so far

That doesn't mean you have added any substance.

 

[tade]

That doesn't mean you have added any substance.

ok, let's take a look at it again then

well, I'm thinking that maybe you might want to not effectively loop back to #8, of you saying "No.", and me asking "hmm how about.." and then it loops back again, and not sure if it really addresses the question, a "vicious circle"

though not meaning to say that someone is at fault, i think that its just the way that it has ended up.

 

[PeterDonis]

me asking "hmm how about.."

Read my response to that in #12 again. If you thought you were proposing some different scenario, you were wrong, and you need to go back and think again.

 

[tade]

ok, let's take a look at it again then

well, I'm thinking that maybe you might want to not effectively loop back to #8, of you saying "No.", and me asking "hmm how about.." and then it loops back again, and not sure if it really addresses the question, a "vicious circle"

though not meaning to say that someone is at fault, i think that its just the way that it has ended up.

hey @DrChinese maybe let's start from #7 and try it out

 

[PeterDonis]

hey @DrChinese maybe let's start from #7 and try it out

The response from @DrChinese in post #6 already answers post #7. So does my response in post #8.

 

[tade]

The response from @DrChinese in post #6 already answers post #7. So does my response in post #8.

oh, from #7 to #6, an instant loop-back

though I'm not sure if it does address, but no worries, i think we can just elaborate and add-on points without much issue

 

[tade]

Read my response to that in #12 again. If you thought you were proposing some different scenario, you were wrong, and you need to go back and think again.

hmm, well, in that case, how about you elaborate on the latter part of #8 referencing on my hopefully elaborations or clarifications of #9 and #11

 

[PeterDonis]

how about you elaborate on the latter part of #8 referencing on my hopefully elaborations or clarifications of #9 and #11

I don't think you quite understand: there are no "elaborations or clarifications" in your posts #9 or #11. Nothing you say in those posts changes my response in post #8 at all. You might want to go re-read that response again and again until its meaning sinks in. I don't think you have fully realized that meaning. It is very general.

i think we can just elaborate and add-on points without much issue

So far you have had zero success in doing this.

 

[tade]

I don't think you quite understand: there are no "elaborations or clarifications" in your posts #9 or #11. Nothing you say in those posts changes my response in post #8 at all. You might want to go re-read that response again and again until its meaning sinks in. I don't think you have fully realized that meaning. It is very general.So far you have had zero success in doing this.

hey cool it with the shade man lol

and just to clarify, by "at all", do you mean keeping #8 just exactly as it is, and no like, adding some elaboration?

 

[PeterDonis]

by "at all", do you mean keeping #8 just exactly as it is, and no like, adding some elaboration?

Yes. The last sentence of post #8 is perfectly straightforward and explicit and needs no elaboration.

 

[tade]

Yes. The last sentence of post #8 is perfectly straightforward and explicit and needs no elaboration.

oh i see, though i feel that despite being straightforward and explicit it could probably benefit more from some elaboration

 

[PeterDonis]

though i feel that despite being straightforward and explicit it could probably benefit more from some elaboration

What kind of elaboration would you like?

 

[tade]

What kind of elaboration would you like?

hmm, well, in that case, how about you elaborate on the latter part of #8 referencing on my hopefully elaborations or clarifications of #9 and #11

oh I'm referring to this

 

[PeterDonis]

i'm referring to this

I've already responded to that. Rather than keep pointing to prior posts that have not gotten across whatever point you think you are trying to make, try making a new post that tries a different way of getting across whatever point you think you are trying to make.

 

[tade]

I've already responded to that. Rather than keep pointing to prior posts that have not gotten across whatever point you think you are trying to make

Yeah no worries I know you already have, I'm just answering your question

 

[tade]

try making a new post that tries a different way of getting across whatever point you think you are trying to make.

ok hmm let's see, I'm finding it kinda hard because of how you're so unequivocal, #22, #24, and not sure what I could do, as I've never encountered anything like this before.

but let me try...

 

[tade]

try making a new post that tries a different way of getting across whatever point you think you are trying to make.

so you said that Bob's ratio of random outcomes only depends on the setting of Bob's polarizer, not on the setting of Alice's, and I was wondering about the entanglement between Alice and Bob, so I was thinking that maybe you could explain about the entanglement together with why Bob's ratio doesn't depend on Alice's settings, and/or about how the inclusion of the special 52/48 polariser may or may not affect things

 

[tade]

@vanhees71 hi, hope I'm not bothering, cos i noticed that you've seen the thread, and i think you're also interested in the field, and so just wondering would like to ask what you think about the OP, thanks

 

[vanhees71]

I've very often expressed my opinion on this topic. For me it is very clear that there's no possibility to send signals faster than light using quantum entanglement. The reason is that this impossibility is implemented in relativistic quantum field theory by the socalled microcausality principle. In my scientific community, high-energy particle/nuclear physics, that's what's called "locality", and this excludes any causal connections between space-like separated events.

The observed long-ranged correlations between space-like separated measurements are due to the preparation of the system in the entangled state and not due to any "spooky action at a distance" of one measurement apparatus at position A on the part of the system at B or the measurement apparatus used at B.

Since thus relativistic local QFT realizes locality via the microcausality constraint on local observables, what one has to give up according to Bell's theorem is "realism", i.e., the assumption that all observables always take determined values, which are only appearing probabilistic because of our ignorance of some "hidden variables".

Whether there are non-local deterministic (realistic) relativistic models in accordance with the observations I don't know.

 

[Nugatory]

But say we have a specially modified or fabricated polariser which can nudge the measurement results from 50/50 either way to 52/48.

Some of the difficulty here is that this nudging violates a basic principle of quantum mechanics, the Born rule. Thus the question is somewhat analogous to asking “say we have a device that violates conservation of energy. Can we use it to build a perpetual motion machine?” and the answer will be the same as you’re hearing in this thread: “Assume what you want, but we still can’t build a perpetual motion machine”.

 

[tade]

Some of the difficulty here is that this nudging violates a basic principle of quantum mechanics, the Born rule. Thus the question is somewhat analogous to asking “say we have a device that violates conservation of energy. Can we use it to build a perpetual motion machine?” and the answer will be the same as you’re hearing in this thread: “Assume what you want, but we still can’t build a perpetual motion machine”.

oh i see, maybe can you elaborate more about the basis behind the Born rule and its exclusion of nudging, thanks