[Alan McDougall (OP)]

Can Causality be violated by say instantaneous quantum entanglement?

Spooky action as Einstein called it or quantum non-locality and entanglement have shown fundamental particles can interact instantaneously regardless of the distance between them. Alter the spin of one particle alters the spin of its twin in the other direction instantaneously.

Causality is fundamental to how the universe works, entropy for instant is intertwined with causality etc.

What are your thoughts on the matter?

Alan

[imatfaal]

Alan - it is an old and untrue chestnut that you can alter the spin of an entangled particle over a great distance.  An entangles pair of particles will be in an indefinite state - in a quantum superposition; the two particles are in a non-classical state where they can seem to be in a mish-mash /combination of states.   if you measure one particle and determine its state the other is (and seeminly always has been) in the opposite state.  But what you cannot say is that the partner changes state (you cannot possibly have measured/have known the state of the distant partner as that would have collapsed the system into two determined states already) - what happens is that the state becomes defined

[Alan McDougall (OP)]

Alan - it is an old and untrue chestnut that you can alter the spin of an entangled particle over a great distance.  An entangles pair of particles will be in an indefinite state - in a quantum superposition; the two particles are in a non-classical state where they can seem to be in a mish-mash /combination of states.   if you measure one particle and determine its state the other is (and seeminly always has been) in the opposite state.  But what you cannot say is that the partner changes state (you cannot possibly have measured/have known the state of the distant partner as that would have collapsed the system into two determined states already) - what happens is that the state becomes defined

I think I know what you mean , that the two particle measures are really like two hands gloves, when you observe the one, the other is always opposite.

However, I am sure that this argument, put forward by no less than Albert Einstein has been disproved.

Alan

[imatfaal]

Alan - it is an old and untrue chestnut that you can alter the spin of an entangled particle over a great distance.  An entangles pair of particles will be in an indefinite state - in a quantum superposition; the two particles are in a non-classical state where they can seem to be in a mish-mash /combination of states.   if you measure one particle and determine its state the other is (and seeminly always has been) in the opposite state.  But what you cannot say is that the partner changes state (you cannot possibly have measured/have known the state of the distant partner as that would have collapsed the system into two determined states already) - what happens is that the state becomes defined

I think I know what you mean , that the two particle measures are really like two hands gloves, when you observe the one, the other is always opposite.

However, I am sure that this argument, put forward by no less than Albert Einstein has been disproved.

Alan

I have given the simplest argument shorn of any details - but it is roughly correct.  I can promise you the notion that you can take an entangled pair, then set spin of particle A, and immediately have spin of particle B taking opposite value IS FALSE. 

[Alan McDougall (OP)]

Alan - it is an old and untrue chestnut that you can alter the spin of an entangled particle over a great distance.  An entangles pair of particles will be in an indefinite state - in a quantum superposition; the two particles are in a non-classical state where they can seem to be in a mish-mash /combination of states.   if you measure one particle and determine its state the other is (and seeminly always has been) in the opposite state.  But what you cannot say is that the partner changes state (you cannot possibly have measured/have known the state of the distant partner as that would have collapsed the system into two determined states already) - what happens is that the state becomes defined

I think I know what you mean , that the two particle measures are really like two hands gloves, when you observe the one, the other is always opposite.

However, I am sure that this argument, put forward by no less than Albert Einstein has been disproved.

Alan

I have given the simplest argument shorn of any details - but it is roughly correct.  I can promise you the notion that you can take an entangled pair, then set spin of particle A, and immediately have spin of particle B taking opposite value IS FALSE. 

Please give source which scientifically proved that " quantum entanglement and non-locality are false?

Alan

[imatfaal]

Alan - this is exactly what I was getting at in the other thread.  No where have I said that quantum entanglement is false.   You need to do a lot of basic reading - what you are describing is not entanglement, it is the common and erroneous conception of what entanglement is.   You cannot change the spin (etc) one of a pair of entangled by acting on the other - what happens is that a nondeterminate quantum mechanical state of superposition is determined into a more classical definite state. 

Alter the spin of one particle alters the spin of its twin in the other direction instantaneously.

You are incorrect.

https://en.wikipedia.org/wiki/Quantum_entanglement

[yor_on]

It's not two gloves Alan, it is only one glove You 'touch' any part of it and its wave function collapse, giving us two particles with opposite spin.

[yor_on]

Don't know what to make of probability though. Take a look at http://xxx.lanl.gov/abs/1111.3328 .What it state seem to be that probability isn't enough in itself. There has to be a underlaying 'reality' for a wave function to exist. In a entanglement it must exist, measuring it you can't state what spin you first will measure, up or down, only that the 'opposite end' of that entanglement either way must have the opposite spin of what you measure.

Using that you can define a entanglement as one wave function, with a equal 'probability' of giving you up, or down. But if a wave function has a hidden demand of being 'real', as that pdf suggest, instead of a mathematical, statistically proven, artifact, then what should a probability mean?

[Alan McDougall (OP)]

It's not two gloves Alan, it is only one glove You 'touch' any part of it and its wave function collapse, giving us two particles with opposite spin.

I know that , but it is imatfaan that thinks that this is the case, I agree with you?

[Alan McDougall (OP)]

Quote from: Alan
    Alter the spin of one particle alters the spin of its twin in the other direction instantaneously.

quote from:imatfaan
You are incorrect.

https://en.wikipedia.org/wiki/Quantum_entanglement

I see how I am incorrect, sloppy wording by me!

When I stated "Alter the spin", I should have said "Measure the Spin" and the other entangled particle always has the reverse spin, semantics really you knew what I meant?

I will use the same above wikipedia link as you did, below

Quantum entanglement occurs when particles such as photons, electrons, molecules as large as buckyballs,and even small diamonds interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description (state), which is indefinite in terms of important factors such as position,momentum, spin, polarization, etc. "(I agree until measured the state of the particle is unknown, my comment Alan)"

Quantum entanglement is a form of quantum superposition. When a measurement is made and it causes one member of such a pair to take on a definite value (e.g., clockwise spin), the other member of this entangled pair will at any subsequent time be found to have taken the appropriately correlated value (e.g., counterclockwise spin).

Thus, there is a correlation between the results of measurements performed on entangled pairs, and this correlation is observed even though the entangled pair may have been separated by arbitrarily large distances. In quantum entanglement, part of the transfer happens instantaneously.

Repeated experiments have verified that this works even when the measurements are performed more quickly than light could travel between the sites of measurement: there is no slower-than-light influence that can pass between the entangled particles.

Recent experiments?? have shown that this transfer occurs at least 10,000 times faster than the speed of light which does not remove the possibility of it being an instantaneous phenomenon, but only sets a lower limit.

Alan

[yor_on]

If we ignore those tries for defining a 'speed' to a entanglement, instead defines it as instant, then one still have to answer what probability now will mean, if that link is correct? Statistically probability means a probability for every action and reaction. It doesn't separate what is possible from what is 'impossible'. more than by the probability given something to happen. But if a wave function only can be real when we find action and reaction realized, then all descriptions of a zero probability, as for example a probability of everything in the universe being entangled, impossible to verify, or why not the wave function of the universe, now should describe something without a wave function. Suddenly the wave function becomes something more than statistics it seems to me?

There is also the problem with me choosing a alternative measurement of a experiment. Depending on that the outcome changes. Either we then have several possible wave functions, all real, of which the one I 'specify' by my measurement becomes a outcome, or? But it makes sense to me to think of a wave function as something 'real', although the way we will define that 'reality' still must become statistics to me.

[dlorde]

I think I know what you mean , that the two particle measures are really like two hands gloves, when you observe the one, the other is always opposite.

However, I am sure that this argument, put forward by no less than Albert Einstein has been disproved.

That would be the 'hidden variable' explanation, the idea that the spin of each particle is determined at entanglement, but unknown until one is measured. You're right that this has been falsified.

An alternative way of thinking of it was mentioned elsewhere on these forums - it's as if there are two pairs of 'potential' particles with opposite spins, and when you make a measurement, you're randomly selecting one pair to be 'real'...

[AndroidNeox]

Entanglement is required by causality. Action at a distance violates relativity because it depends on the existence of a universe time standard (simultaneity).

[Alan McDougall (OP)]

Entanglement is required by causality. Action at a distance violates relativity because it depends on the existence of a universe time standard (simultaneity).

As far as I know there is no such thing as  ' universal time standard" .This was Isaac Newtons idea of how time worked. Einstein "General relativity" proved this wrong Maybe I have misunderstood what you have stated?

If a reaction is instantaneous, what caused it to happen at the exact some moment in time?

Alan

[yor_on]

I think you two agree, reading you?

Simultaneity may have existed just after a Big Bang, if we assume that 'place' to be perfectly isotropic, uniform and homogeneous. If it was it seems to me that you can define it as being at rest with itself. If that is true we can define that state as one single frame of reference. Then all clocks was perfectly synchronized at that 'time'. but as soon that you introduce two frames of reference, comparing, you must find time dilations, Lorentz contractions. If you don't accept this definition you can still define both as belonging to a same 'frame of reference', no matter what distance you find between them.

As always we forget the third part though, you measuring, using that local clock and ruler.

[Alan McDougall (OP)]

I think you two agree, reading you?

Simultaneity may have existed just after a Big Bang, if we assume that 'place' to be perfectly isotropic, uniform and homogeneous. If it was it seems to me that you can define it as being at rest with itself. If that is true we can define that state as one single frame of reference. Then all clocks was perfectly synchronized at that 'time'. but as soon that you introduce two frames of reference, comparing, you must find time dilations, Lorentz contractions. If you don't accept this definition you can still define both as belonging to a same 'frame of reference', no matter what distance you find between them.

As always we forget the third part though, you measuring, using that local clock and ruler.

Before our universe emerged out of the primordial singularity, time did not exist, so I think that in reality only in this state, the only true, "actual single discrete moment" that ever existed, was then. After all if time did not flow, then, the primordial singularity, was stuck in a "moment" (Sloppy wording sorry for that.). Until something caused it to emerge and create our universe, (Big Bang/Emerge/ you choose?) No third party was there as far as I know?

Just a note of mine! There was never such an events a "big bang", this is as best,  loose terminology, in my opinion.

Alan

[yor_on]

I think so too Alan To get something, as this universe, you must have a arrow existing to express outcomes in. So that original 'moment in time' must start when we get a first outcome. What was before that I don't know, quantum logic? But it should have nothing to do with our definitions of a arrow.

Statistics is a little like a detective to me, studying the past to define a future. Then, using this definition we must have a arrow to get to QM. So, one could also presume that the logic defined through such a arrow might be something preexisting, although not defined in specific outcomes, even before a Big Bang?

[Pmb]

Can Causality be violated by say instantaneous quantum entanglement?

Spooky action as Einstein called it or quantum non-locality and entanglement have shown fundamental particles can interact instantaneously regardless of the distance between them. Alter the spin of one particle alters the spin of its twin in the other direction instantaneously.

Causality is fundamental to how the universe works, entropy for instant is intertwined with causality etc.

What are your thoughts on the matter?

Alan

It can't be said that the measurement of the spin of one particle causes something to happen with the other one simultaneously. Recall that simultaneous is observer dependant so what is simultaneous in one frame is not simultaneous in another frame
(depending on the frame of course). Griffith discusses this in his QM text.

[yor_on]

Pete , would you agree to that causality, and a arrow of time, must exist for both observers, to get to a logic?

Meaning that you can exchange definitions (coordinate systems), and relate them through Lorentz transformations? If that is true, then we have a arrow as I see it, and pointing in one direction (locally defined), as well as 'globally'. I have still to see someone (not you, just someone:) define a arrow going 'backwards' experimentally. Also, to me 'simultaneity' is not the same as 'the arrow of time'. I think of a arrow as something defining a logic. We can play it backwards and it 'must' make sense then too, if it didn't it would fail as a logic.

[yor_on]

Although, if you take such a reasoning under Planck scale, it becomes meaning less, as I think. We get this arrow from frames of reference, assuming one single frame then to be related to Planck scale we lose that arrow under, and at, it.