[Petrochemicals (OP)]

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 ?

[Colin2B]

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 don’t 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, don’t understand what you are trying to do.

If not how can quantum entanglement be proven without information ?

it can’t.
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.

[jeffreyH]

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

EDIT: This is important with respect to local realism.

[Petrochemicals (OP)]

.

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, don’t 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.

[Kryptid]

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.

[Colin2B]

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 don’t 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.

[yor_on]

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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[Petrochemicals (OP)]

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

[CPT ArkAngel]

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...

[evan_au]

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

[yor_on]

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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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.

[yor_on]

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.

[Petrochemicals (OP)]

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.

[yor_on]

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.

[yor_on]

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.

[yor_on]

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?

[Colin2B]

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).
Let’s 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 doesn’t.

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 don’t 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 isn’t too circular.
Yes, it is possible to discuss probability in the abstract, but what do you mean by probability existing?

[yor_on]

" 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.

[yor_on]

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 :)

[yor_on]

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.