Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Petrochemicals on 10/11/2019 00:32:45

Title: How can quantum entanglement be proven?
Post by: Petrochemicals on 10/11/2019 00:32:45
I know that quantum entanglement is not possible of conveying information without knowing the state of the particles before hand, but is it possible to observe a particle held in static state, get on a bus to the other particle, and then use the particle to relay information. If not how can quantum entanglement be proven without information ?
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 10/11/2019 01:09:47
I know that quantum entanglement is not possible of conveying information without knowing the state of the particles before hand,
The whole point of entanglement is that you donít know the state of either of the particles before hand, but when you discover the state of one of them you immediately know the state of the other.

but is it possible to observe a particle held in static state, get on a bus to the other particle, and then use the particle to relay information.
sorry, donít understand what you are trying to do.

If not how can quantum entanglement be proven without information ?
it canít.
The information you need is:
- that 2 particles are entangled ie they have correlated states.
- the exact type of correlation
- measuring the state of the 2 particles then confirms the correlation.
Title: Re: How can quantum entanglement be proven?
Post by: jeffreyH on 10/11/2019 01:19:43
Two fermions in close proximity cannot share the same quantum state. If their paths then diverge one will be spin up and the other spin down. Measuring one will tell you the state of the other.

However, this trivialises the phenomena. See: https://en.m.wikipedia.org/wiki/Quantum_entanglement (https://en.m.wikipedia.org/wiki/Quantum_entanglement)

EDIT: This is important with respect to local realism.
Title: Re: How can quantum entanglement be proven?
Post by: Petrochemicals on 10/11/2019 01:41:41
.

but is it possible to observe a particle held in static state, get on a bus to the other particle, and then use the particle to relay information.
sorry, donít understand what you are trying to do.

If you knew the state of one particle,  then observing the other particle  you should know how the first particle is behaving. If you cannot do this how is it proven? Surely this could convey information.
Title: Re: How can quantum entanglement be proven?
Post by: Kryptid on 10/11/2019 01:48:52
Surely this could convey information.

The reason you can't use this to convey information is because you can't force the particle to be in a particular state. It's random.
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 10/11/2019 08:35:59
If you knew the state of one particle,  then observing the other particle  you should know how the first particle is behaving. 
As explained by @Kryptid the 2 particles (if we simplify things and take an example of electrons) are in opposite states (to be strictly correct they are in a superposition of correlated but opposite states) but you donít know which state either one is in until you check it out.

Surely this could convey information.
When you check out either one you know the state of the other, in other words acquiring information on one gives you information on the other.

As @jeffreyH says, there are additional complexities, but at a basic level this is how it works.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 10/11/2019 16:23:24
The whole point of a quantum entanglement is that you don't know what spin this particle you measure will have, it has a fifty fifty percentage in a simplest case of being 'up' or 'down', and you can do the a same experiment with a same collection of particles several times to find that sometimes they are 'up' and sometimes they are 'down'.

What you do know is that the other 'particle' split from the original through a beam divider of some sort 'instantly' will know its partners spin as soon as you measure the first one. Measuring it collapses the probabilities it contained, and for its 'twin' too. But before that measurement nothing was sure.
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And yes, the whole question becomes one of how it could 'know instantly' what spin its partner would present. As for information the idea is that this won't be allowed as it is 'ftl'. Information is presumed to have a 'speed' no higher than 'c'. But then you have the injection of 'energy' as you measure it (bump it), and that's something I wonder about. Will its partner gain energy too? Or is there no 'energy' involved in this measuring?

the point of that question is one of if we still can 'separate' them from each other, or if they are 'indivisible'. There is a difference I think? You could also call it a question of 'information'  and 'speeds' ..

And yes, if someone knows of a experiment checking this I would be very interested. But it has to be a classic one in where we separate the particles a fair distance. both in 'splendid isolation' before measuring, also defining their energy before a measurement, then adding whatever 'kinetic energy' we create in our first measurement, comparing it to its twin. As it is our interference with their indeterminate state that defines the 'wave collapse' the 'spin' of the first is not the interesting factor here, we can shoot the first one with a laser if we like as long as we know the energy it contained before. And it's not the spin of its twin that we are interested in anymore, just its energy.

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Title: Re: How can quantum entanglement be proven?
Post by: Petrochemicals on 26/11/2019 22:12:02
Surely this could convey information.

The reason you can't use this to convey information is because you can't force the particle to be in a particular state. It's random.
You see, that sounds a bit defeatist. If you could force/hold a particle until you could convey the other particle/state to one light year distance you can convey information, or you can not prove entanglement anyway
Title: Re: How can quantum entanglement be proven?
Post by: CPT ArkAngel on 27/11/2019 09:08:52
The problem doesn't necessarily involve randomness. The fact is you cannot measure the initial state of any particle because it would break the entanglement (decoherence). If you want to send a signal to someone else, you must use a communication protocol. To use a protocol, you must fix the initial states but then the particles are not entangled anymore.

This also means you cannot prove that energy is exchanged at a speed faster than light, because you must know the initial states to do so.

There is also another big loophole. According to the usual interpretation, when one particle is entangled with another one, they are supposed to be entangled at 100%, meaning they are opposite to one another considering a particular type of state like the spin. The problem is the detectors should become entangled with the particles while they are detected. This would lead to a measurement of a fraction of the original entanglement state mixed with a fractional complement coming from the detector. Solving the wave equation gives an answer which includes everything implicitly without informing you how this works, especially how the detectors are included or if you prefer, in which part they are involved. For example, the initial particles could be entangled only at 50%, meaning if one is up, the other has necessarily a non-zero down component. Then if both detectors are at the same angle and if the measurement is mixed at 50% with the detector component, you can obtain the same results if you suppose a uniform (random-like) distribution of the initial states. In this scenario, the entanglement relations could be a static spatial component with no energy and it can follow classical laws with just a quantization twist. States follow classical laws but with quantized steps... It could be the origin of the Born rule. You may not know the initial states of the particles but you know the states of the detectors...
Title: Re: How can quantum entanglement be proven?
Post by: evan_au on 28/11/2019 08:06:44
Quote from: yor_on
is there no 'energy' involved in this measuring?
Yes, it takes a minimum amount of energy to measure the state of a system.

If there is far more energy/power available from the source than this minimum, then it is possible to power the receiver from the "excess" received power. But then your maximum information transfer rate is much lower than if the receiver were locally powered.
See: https://en.wikipedia.org/wiki/Eb/N0
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 28/11/2019 16:46:05
Hmm, already answered that one I see, still this is slightly different so I'll let it be.

Yes it is petrochemicals. But what you did was all inside 'c', getting on that bus to the other particle to then transmit 'information' by measuring it. Normally one have to presume that neither of those particles have been 'touched' before that moment, but in this case it won't matter presuming another person looking at the other particle at some predefined time, just after you.

the reason to why it won't matter is that the spin is unknowable before a measurement. And as you in this case always will know that it will be a opposite the only thing mattering is your predefined agreement. The only 'information' taken from it will be, if you compare notes afterwards, that those spins once again was opposite.

Another thing about the suggestion is that nothing stops information unless it surpass 'c'. In this case it was all done under 'c' and so a phone call would have been just as easy.
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syntax

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you mix definitions there Petrochemicals, a entanglement is proven through measurements. That is indeed 'information' that physics is interested in. But it doesn't state that by knowing this we also have 'transmitted' information using those  particles spin.

actually it won't matter for it when he look, before you or after. The result will still be the same. Opposite spins. As long as you compare notes that is.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 29/11/2019 14:23:16
What is interesting is if it is 'predefined spins' or a result of probabilities solely. It can be both of course, a 'law' demanding that the spins must be opposite, any which way probability then presents them to us. In that case it becomes slightly different because the spin, even if following probability, should then not be a mean of transferring f.ex kinetic energy when probed.

There is also a possibility of those spins being 'set' at the interaction with f.ex a beam splitter which should lead to the same observation. No 'kinetic energy' transferable. What that would mean is the the spins no longer is a result of 'chance' aka probability

The first one, where it is a 'law' seems to imply that nature don't accept 'identicallity'.
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The whole point of it is the idea where it is the 'observation' that force the outcome of spin. Looked at that way there should be a possibility of kinetic energy being transferable as we then treat both particles as parts of a same 'system'. If that was possible I don't know if that is information or not. It becomes something of a grey zone to me Petrochemicals.

Mathematically is is treated as a result of superpositions of both particles spin. Together it becomes 'null' and for that to happen they can't have a same spin. One spin taking out the other so to speak. That way to treat it also imply that it's a 'whole system' instead of 'unique particles' which makes the idea of kinetic energy being transferable interesting to me.
Title: Re: How can quantum entanglement be proven?
Post by: Petrochemicals on 30/11/2019 01:10:34
Quote from: yor_on
is there no 'energy' involved in this measuring?
Yes, it takes a minimum amount of energy to measure the state of a system.

If there is far more energy/power available from the source than this minimum, then it is possible to power the receiver from the "excess" received power. But then your maximum information transfer rate is much lower than if the receiver were locally powered.
See: https://en.wikipedia.org/wiki/Eb/N0
That sounds like instantaneous energy transfer, thus information.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 03/12/2019 21:02:06
Maybe?

If we treat a entanglement as consisting of two particles over a distance, both gaining energy due to the probing of one then what is 'transferred' isn't anything of a particle nature, it's still 'energy'. What created it was a interaction but the new state of the 'far away particle' won't contain any new information even though being of a higher energy than before the other particles probing. And whatever type of information you can get from that particle will need to be a result of interactions under 'c', as for example probing that one too, to see if it reached a new energy. So all of it falls under 'c' as far as I get it, except the initial probing that created a new state.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 08/12/2019 20:55:30
What I think it would confirm, or disprove, is the idea in where you look at 'both particles' as 'separate' with a faster than light communication. If it gains energy then it should be 'one particle', and to then argue that they are separate and need ftl to 'exist' seems counterintuitive to me.
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Actually, if the last one is true then it should put our notions of what a 'space' is upside down. I've seen some involved in quantum logical computers state that it will be impossible to create machines involving more than just a few entangled particles due to the impossibility of error corrections. And if so a 'system' of complex entanglements also becomes 'forbidden territory', just as black holes can be seen to be. And you can't use it for transferring energy either without you needing to create complex configurations of particles. It's on the whole a impractical use of transfer anyway.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 08/12/2019 21:28:11
What that could be seen to state is that decoherence is the reason why we exist, and that it holds even on a quantum mechanical scale, not due to (what) magnitude of (geometrical) scale but to magnitude of possibilities.

If one think that one through it then seem possible (in theory) to decouple a geometrical space from a probability space. Meaning that the (magnitude of) probability of something may lead to a geometrical space? And that one is truly weird.
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What it falls down to is how you would see those 'interactions' producing a 'outcome. Because that is what it is about. In normal binary computing there are error corrections inbuilt in the code creating your operative system. In a quantum computer it's about 'super positions' instead, allowing each 'quantum bit' to be undefined until 'measured', it's neither one nor null, but the slightest interference will set it, and without you being able to correct it. So either we define the interference possible to the existence of a geometrical space containing 'particles',  or,   a probability space doesn't need a geometrical space, although its outcomes do.
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Maybe it's better as a question?

Must a probability have a geometrical space to exist?
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 08/12/2019 22:30:31
If it gains energy then it should be 'one particle', and to then argue that they are separate and need ftl to 'exist' seems counterintuitive to me.
There is no evidence that one particle gains energy if energy is added to the other.
That would mean there would be a theoretical means of detecting a signal and refute the no signalling theorem (unless of course QM is not a complete theory, in which case hidden variables apply and the no signalling theorem is invalid).
Letís take for example 2 electrons entangled with opposite (or even the same) spin. To measure the spin of one we have to pass it through a spin detector which causes it to deviate from its path. If energy was transferred to the other electron we would expect it to deviate from its path before being measured, but it doesnít.

If one think that one through it then seem possible (in theory) to decouple a geometrical space from a probability space. Meaning that the (magnitude of) probability of something may lead to a geometrical space? And that one is truly weird.


Must a probability have a geometrical space to exist?
I donít follow what you are trying to say.
Probability space is a description of the probability of some event or sequence of events occurring. Those events (even QM events) occur in geometric space, which is where we observe their occurrence - if that isnít too circular.
Yes, it is possible to discuss probability in the abstract, but what do you mean by probability existing?
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 10/12/2019 08:59:10
" That would mean there would be a theoretical means of detecting a signal  "

You're thinking of using different energy levels as a mean of communication? That's interesting and would show Petrochemicals approach to be correct. And I think it would be possible presuming we create several entanglements foreknowing their 'base energy' to then measure them. So then it shouldn't be possible at all as we define useful communication to be limited to 'c'. So do you know of any experiments taking into consideration the amount of energy injected in a measurement Collin?
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the reason is about how one should think of it, a entanglement as a 'indivisible particle' or as 'individuals' showing a correlation. In the first case 'injections' should 'transfer', in the other it's not necessary.

Because I still want to know if it happens, or not.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 10/12/2019 09:08:10
And the rest of it is just speculation Collin, It was something that struck me as I wrote. And it goes back to the way relativity express itself.
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andf by that I mean that I still need to think about it before I'm saying more :)
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 10/12/2019 10:14:20
More explicitly. If it could be seen as 'indivisible system' it would question what we mean by our geometry, and nota bene, that it do even if the 'communication' we wonder about isn't 'useful' And so energy injected becomes interesting in this case, because it can't be a 'indivisible system' if the energy injected isn't existing in your other measurement.. The idea behind it all is that this is a 'instantaneous action' although non-useful, which, if one now want to argue that the wave collapse is faster than the 'energy' one injected will get into a really absurd argumentation of what one then should mean by 'instantaneous'.

It clears up one thing I think, testing for it, and I totally missed the way you could use it for communication. But then again, I came to it from another perspective.
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Actually, arguing that the wave collapse is faster than the injection pretty much states that you don't need a injection for the collapse. That is, a reaction without a action.
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 10/12/2019 12:08:22
" That would mean there would be a theoretical means of detecting a signal  "

You're thinking of using different energy levels as a mean of communication? So do you know of any experiments taking into consideration the amount of energy injected in a measurement Collin?
What I'm saying is that the no signal theorem says such communication - using energy or anything else - is not possible. The spin experiment I described shows there is no energy transfer.
If you look at the QM descriptions of the particle states you will see that there is no suggestion that anything changes for the particles, just our knowledge of the states.

the reason is about how one should think of it, a entanglement as a 'indivisible particle' or as 'individuals' showing a correlation. In the first case 'injections' should 'transfer', in the other it's not necessary.
Not sure what you mean by 'indivisible particle'. QM says that the 2 particles are described by a single wavefunction, but that's not the same thing as an indivisible or connected particle. It is however, the same as 2, as yet unmeasured, particles showing a correlation.
As @alancalverd has said in the many worlds thread, the descriptions in QM are about how we handle probabilities and correlations.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 10/12/2019 12:55:44
Which experiment are you referring to Collin? As far as I know the spin doesn't depend on the energy of a entanglement?

The last part goes back to a discussion I had with JP.
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If you know of such a experiment and can link I would be pleased.
btw: that should tell you how long I've been wondering about it, me referring to JP :)

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Heh :)
I'm lazy, I should have checked it up earlier, a lot earlier.

https://www.technologyreview.com/s/417362/physicist-discovers-how-to-teleport-energy/

Then again, it shouldn't be able to transmit information, just as you state. I'll need to look into that, and so do you I guess.
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 10/12/2019 15:24:46
As far as I know the spin doesn't depend on the energy of a entanglement?
No, it doesnít, but the measurement does cause a change of direction (momentum) of the measured electron (as I described in previous post) which is not reflected in the momentum of the other electron.

https://www.technologyreview.com/s/417362/physicist-discovers-how-to-teleport-energy/
You have to be careful regarding what is written in reports of experiments rather than what is written in the actual paper. I read this paper way back and read:
ďHere it should be emphasized that this output energy existed not at A but at B even before the start of the protocol and was hidden in- side the zero-point fluctuation of B. Of course, this zero-point energy is not available by usual local operations for B. However, by using a local operation dependent on Aís information, it becomes possible to dig out Bís zero-point energyĒ
In other words, no energy is transmitted.

It is worth remembering that quantum teleportation is not a transfer of a particle from one place to another, but a duplication of the state of one particle imposed on another, using data transmitted over a classical link.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 11/12/2019 00:37:24
Sure, I'm not saying that it it will be there just because a paper suggest a theoretical possibility. But what it say, as far as I've read, is that the injection adds 'energy' that wasn't there before, and that it will be this added energy that is lifted out.

" the process of teleportation involves making a measurement on each one an entangled pair of particles. He points out that the measurement on the first particle injects quantum energy into the system. He then shows that by carefully choosing the measurement to do on the second particle, it is possible to extract the original energy."

I told why I was interested , and that the idea of communication wasn't wherefrom I came to it. That seems to be your angle of attack on this,  but mine was just a question of it was possible to extract 'energy' from the injection of  energy done by a measurement.
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But yes, you make a interesting point there. If now momentum isn't 'replicated', why should energy be so?
Let's assume that energy is 'replicated' but not momentum, what would be the reason?
Another question I'm afraid :)

And I suppose one would have to differ between light and mass when it comes to that. A added momentum to light should just blueshift it I think? But when it comes to a proper mass particle it should also be 'deflected' by the measurement, as you say.


Do you have a link to where that is tested Collin? Where they checked for it I mean?
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 11/12/2019 00:43:55
And I don't get where you get this 'classical link' in that paper, or maybe you're pointing out what both you and me actually agree on. That it shouldn't be possible to transmit useful information other than classically.  Seem's like we're talking of two different subjects.
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 11/12/2019 10:03:40
And I don't get where you get this 'classical link' in that paper,
The classical link is standard for all quantum teleportation, itís the way it works. It will be mentioned somewhere in the paper, but probably in passing. Remember, you are not transferring an electron from A to B, just duplicating the state of A to the state of B.
See this diagram:
https://en.m.wikipedia.org/wiki/File:Quantum_teleportation_diagram.PNG

I told why I was interested , and that the idea of communication wasn't wherefrom I came to it. That seems to be your angle of attack on this,  but mine was just a question of it was possible to extract 'energy' from the injection of  energy done by a measurement.
No, my angle isnít to do with communication, but transfer of energy. As the paper points out, no energy is transferred from A to B.
Yes, the measurement extracts energy (at the remote location) that wasnít accessible by other means. Thatís what the paper says.

Do you have a link to where that is tested Collin? Where they checked for it I mean?
It is standard method for measurement of spin. Pass the electron through a mag field it deviates either N or S (up or down). Of course, if you rotate the magnets you get a different basis and different measurement which causes a lot of confusion for some people. Same happens with photon polarisation.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 11/12/2019 16:47:51
Seems we have to agree on disagreeing here Collin, as far as I get you you define it as only (theoretically) extracting the energy of the 'second particle'? Or do you read it as it extract more that that, but not the injected energy?

When I read " As the paper points out, no energy is transferred from A to B.
Yes, the measurement extracts energy (at the remote location) that wasnít accessible by other means. Thatís what the paper says. "

then  I get confused?

If it only extract the energy of the 'second particle' without that particle having gained anything by being entangled the whole paper makes no sense. That's the energy of a untangled particle in such a case.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 11/12/2019 16:52:32
And yes, forgot about that one, but have they measured the deviations?
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And you keep referring to the standard classical approach for this paper? There is no stl (slower than light) information involved in it as far as I've seen?
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 11/12/2019 17:08:32
 " The relationship between energy and information has been investigated extensively in the context of computation energy cost including a modern analysis of Maxwellís demon [1]-[2]. In this Letter, we show a new energy-information relation from a different point of view. Recently, it has been reported that energy can be transported by local operations and classical communication while retaining local energy conservation and without breaking causality [3]-[5]. Such protocols are called quantum energy teleportation (QET) and are based on ground-state entanglement of many-body quantum systems including spin chains [3], cold trapped ions [4] and quantum fields [5].

By performing a local measurement on a subsystem A of a many-body sys-tem in the ground state, information about the quantum fluctuation of A can be extracted. Because the post-measurement state is not the ground state in general, some amount of energy is infused into A as QET energy input during this measurement, and the ground-state entanglement gets partially broken. Next, the measurement result is announced to another subsystem B of the many-body system at a speed much faster than the diffusion velocity of the energy infused by the measurement. Soon after the information arrives at B, energy can be extracted from B as QET energy output by performing a local operation on B dependent on the announced measurement data. The root of the protocols is a correlation between the measurement information of A and the quantum fluctuation of B via the ground-state entanglement. Due to the correlation, we are able to estimate the quantum fluctuation of B based on the announced information from A and devise a strategy to control the fluctuation of B. By the above-mentioned selected local operation on B, the fluctuation of B can be more suppressed than that of the ground state, yielding negative energy density around B in the many-body system.

The concept of negative energy density has been investigated in quantum field theory for a long time [6]. Quantum interference among total energy eigenstates can produce various states containing regions of negative energy density, although the total energy remains nonnegative. The regions of negative energy density can appear in general many-body quantum systems by fixing the origin of the energy density such that the expectational value vanishes for the ground state. In spite of the emergence of negative energy density, the total energy also remains nonnegative for the general cases. In the QET protocols, during the generation of negative energy density at B, surplus positive energy is transferred from B to external systems and can be harnessed as the QET output energy. Here it should be emphasized that this output energy existed not at A but at B even before the start of the protocol and was hidden inside the zero-point fluctuation of B. Of course, this zero-point energy is not available by usual local operations for B.

However, by using a local operation dependent on Aís information, it becomes possible to dig out Bís zero-point energy by pair creation of the positive output energy from B and the negative energy of B. Hence, we do not need to hire any physical carrier of energy from A to B like electric currents and photons, at least, during short-time QET processes. Needless to say, after the completion of QET process, the positive energy of A compensates for the negative energy of B during late-time free evolution of the many-body system. The amount of output energy from B is upper bounded by the amount of input energy to A. "
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 11/12/2019 17:15:17
But it also seem to allow for a communication FTL?
Didn't think about that before you posted your objection Collin.
I'm not sure at all about this paper, but then again it's about that 'coin of exchange' as JP used to call it

 'energy'
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From my own point of view It shouldn't be doable, if one gain a information protocol (FTL) by it. So if this works then there has to be something more involved in it, making it impossible to use as a information source.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 11/12/2019 18:18:29
Although, thinking of it, all entanglements where you 'know' when to measure on the 'second particle' involves a slower than light arrangement, where you set a time for A and a time for B.  So there is always a 'classical conection' between the two, even if not measured on yet.
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that is to say, to 'construct' a entanglement is to use classical information. Or better expressed, measuring on them getting a outcome, is a result of a prearranged construction and order of causality. And that one is still classical even if the opposite 'spins' found are instantaneous.
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 11/12/2019 22:57:59

but have they measured the deviations?
Yes, should be in most textbooks. You get an eye diagram, one line above one below axis depending on whether up or down spin.

And you keep referring to the standard classical approach for this paper? There is no stl (slower than light) information involved in it as far as I've seen?
Classical means light speed or slower, not just stl.
Classical is mentioned right up front.
From paper:
ďAbstract
Protocols of quantum energy teleportation (QET), while retaining causality and local energy conservation, enable the transportation of energy from a subsystem of a many-body quantum system to a distant subsystem by local operations and classical communication through ground-state entanglement. ........Ē


Look at the diagram I sent, it shows the classical data channel which is part of all teleportation experiments.

Seems we have to agree on disagreeing here Collin, as far as I get you you define it as only (theoretically) extracting the energy of the 'second particle'? Or do you read it as it extract more that that, but not the injected energy?
No, the paper says extract the same amount of energy at B as was input at A. I have highlighted in the quote you gave:
" The relationship between energy and information has been investigated extensively in the context of computation energy cost including a modern analysis of Maxwellís demon [1]-[2]. In this Letter, we show a new energy-information relation from a different point of view. Recently, it has been reported that energy can be transported by local operations and classical communication while retaining local energy conservation and without breaking causality [3]-[5]. Such protocols are called quantum energy teleportation (QET) and are based on ground-state entanglement of many-body quantum systems including spin chains [3], cold trapped ions [4] and quantum fields [5].

By performing a local measurement on a subsystem A of a many-body sys-tem in the ground state, information about the quantum fluctuation of A can be extracted. Because the post-measurement state is not the ground state in general, some amount of energy is infused into A as QET energy input during this measurement, and the ground-state entanglement gets partially broken. Next, the measurement result is announced to another subsystem B of the many-body system at a speed much faster than the diffusion velocity of the energy infused by the measurement. Soon after the information arrives at B, energy can be extracted from B as QET energy output by performing a local operation on B dependent on the announced measurement data. The root of the protocols is a correlation between the measurement information of A and the quantum fluctuation of B via the ground-state entanglement. Due to the correlation, we are able to estimate the quantum fluctuation of B based on the announced information from A and devise a strategy to control the fluctuation of B. By the above-mentioned selected local operation on B, the fluctuation of B can be more suppressed than that of the ground state, yielding negative energy density around B in the many-body system.

The concept of negative energy density has been investigated in quantum field theory for a long time [6]. Quantum interference among total energy eigenstates can produce various states containing regions of negative energy density, although the total energy remains nonnegative. The regions of negative energy density can appear in general many-body quantum systems by fixing the origin of the energy density such that the expectational value vanishes for the ground state. In spite of the emergence of negative energy density, the total energy also remains nonnegative for the general cases. In the QET protocols, during the generation of negative energy density at B, surplus positive energy is transferred from B to external systems and can be harnessed as the QET output energy. Here it should be emphasized that this output energy existed not at A but at B even before the start of the protocol and was hidden inside the zero-point fluctuation of B. Of course, this zero-point energy is not available by usual local operations for B.

However, by using a local operation dependent on Aís information, it becomes possible to dig out Bís zero-point energy
by pair creation of the positive output energy from B and the negative energy of B. Hence, we do not need to hire any physical carrier of energy from A to B like electric currents and photons, at least, during short-time QET processes. Needless to say, after the completion of QET process, the positive energy of A compensates for the negative energy of B during late-time free evolution of the many-body system. The amount of output energy from B is upper bounded by the amount of input energy to A. "
Remember, all you are doing is measuring the state of A, sending info about that to B so that you can operate on B and put it into the same state as A. See above where it says ďby using a local operation dependent on Aís information, it becomes possible to dig out Bís zero-point energyĒ.

But it also seem to allow for a communication FTL?
I donít see that it says that anywhere. Can you point it out?

Although, thinking of it, all entanglements where you 'know' when to measure on the 'second particle' involves a slower than light arrangement, where you set a time for A and a time for B.  So there is always a 'classical conection' between the two, even if not measured on yet.
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that is to say, to 'construct' a entanglement is to use classical information. Or better expressed, measuring on them getting a outcome, is a result of a prearranged construction and order of causality. And that one is still classical even if the opposite 'spins' found are instantaneous.
Thatís not what is being done here.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 15/12/2019 18:46:24
I see your point Collin. You define this experiment as resting on a classical channel if I read you right. That you will need to foreknow the energy put into the entangled system to be able to extract the same energy at 'B'. If it is that way it leads to the idea of using it as a (FTL) communication meaningless, which I have to admit please me :) Didn't think of that question in form of communication before I read your post.

and no matter what, it is what I originally was wondering about, how one should think of a entanglement. As being 'two particles correlated' or as being 'one indivisible'. Because if you can treat this 'system' in such a way that it allow you to extract more energy than what 'B' initially, before the measurement on 'A', contained then there it is a difference, at least to me.
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The difference being that although you can't disprove the idea of something getting correlated at its origin, aka a beam through a beam splitter, the later improvement in where energy injected at 'A' while measuring it becomes extractable at 'B' points to it not being so. Unless you want to question causality / time but that will only make it even more complicated.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 15/12/2019 18:50:06
But it also makes the idea of a particles 'intrinsic energy' questionable, doesn't it? After all, everything, presuming f.ex light (photons) and atoms to be 'time less' should be entangled at a Big Bang.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 15/12/2019 19:01:05
And I'm still not sure how to read that paper?
The wording creates a ambivalence.

As this " Next, the measurement result is announced to another subsystem B of the many-body system at a speed much faster than the diffusion velocity of the energy infused by the measurement."

First of all it defines it as being a 'speed', wherefrom comes that conclusion?
And a diffusion velocity of energy inside one particle?

you can read that as if it is meant to be a transfer FTL, but I don't see how that conclusion comes to be.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 15/12/2019 22:46:33
And Collin, do me the favor of presuming that I do know the difference between the speed of light in a vacuum as defined locally versus something above that limit.
Title: Re: How can quantum entanglement be proven?
Post by: yor_on on 15/12/2019 23:12:03
Damn, this is incredibly embarrassing. I already wrote about this at another site a long time ago. And there I had no problem with the classical definition you use although I found some problems with the idea of it 'lifting out energy' of this vacuum. Here's another paper from him where he describes it more in detail, and where he state what you state too, that it involves a classical channel.

http://www.tuhep.phys.tohoku.ac.jp/~hotta/extended-version-qet-review.pdf

I'll blame it on senility being a burden we all will share :)
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Hmm, I've been away from entanglements for a rather long time. I mean really thinking about it.
Here's a twist.

=========================
"
    If I get it right the idea is that without a sub-channel for each entanglement the 'receiver', inadvertently, might end up as the sender?

    Assume that I have a 'timer' at the receivers end, and ten entanglements. The sender send one sub-message, defining a time rate, which the receiver then set the timer to. The timer then proceed to measure each of the entanglements successively according to the defined time rate. Would that still be a 'indeterministic flow', or is it something more I'm missing here?

    ...

    This is tricky.

Yep, a bit!

If you set up a prearranged timing between A and B, the net "energy" received by B will approach zero in all cases. Hotta's trick is to tell B the proper measurement basis for each individual trial. Because each AB pair is different, of course! A pre-arranged plan gets you nothing, the results are simply random! Instead, A tells B what to expect, and B responds accordingly knowing the now predetermined outcome.

It is important to note that is is NOT true that applying some energy at A causes energy to appear at B. It does not matter how much energy is invested by A, that does not change what occurs at B. That is NOT the mechanism.

Honestly, this is a very complex subject and all I can really tell you is that calling it Energy Teleportation is misleading as a lay term. This is a scientific label, and you should not take it too seriously. "
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What one might do is to connect it to Jeffreys post about 'Quantum Bayesianism'. https://en.m.wikipedia.org/wiki/Quantum_Bayesianism   versus  ' the many worlds theory ' https://www.thoughtco.com/many-worlds-interpretation-of-quantum-physics-2699358

And why you might want to do this should be depending on how you look at those theories. If you go out from a definition in where your expectations defines the outcome, or at least influence it, then the idea of each arrangement having its own unique identity?

From the position of A, everything will be delivered as arranged once and for all by this first stl (including at 'c':) 'sub-channel' presenting the arrangement, if I'm thinking right here. From the position of 'B' though, measuring as defined by 'A', (assuming causality to exist between them and so a possibility for those to define each others time) it then becomes a test of those ideas. In a many worlds theory you can't define your own as the 'primary' link of a chain of bifurcations, even though we take it for granted as that is what probability state. So presuming probability to hold, there should be a possibility of finding that sequential prearranged ordering of measurements to deliver you energy, as it seems to me. (as a statistical possibility)

In the other case where your expectation influence the experiment, then it comes down to what those expectations are, doesn't it?
 

In other words, it comes down to the statistics of those experiments, done until you get a significant amount of them. That is if I'm thinking right here? All of this presuming the paper to be correct otherwise.

Or, a entanglement is independent of those theories?
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Actually it becomes even murkier than that if you define it such as with a sub channel working you can lift our 'energy' of a vacuum. Energy conservation ignored, it's still about your intention, isn't it? The sub channel doing one thing, enabling you by it's expressed intention to find energy that otherwise wouldn't be found. I have to admit that I find that paper hard to swallow. And yes, that's also the way I connected it to 'Quantum Bayesianism' versus 'many worlds'.
Title: Re: How can quantum entanglement be proven?
Post by: Colin2B on 16/12/2019 09:02:38
And Collin, do me the favor of presuming that I do know the difference between the speed of light in a vacuum as defined locally versus something above that limit.
I would always do that, but with my TNS education hat on I am always looking at how our interested readers are interpreting what they read here, or might misinterpret.
I agree quantum teleportation is poorly named and had almost said the same thing; quantum photocopying more like.