Is quantum entanglement at a distance evidence that entanglement can't be the answer

[robinpike]

When Alain Aspect in 1982 (and others since and before) performed quantum mechanical experiments (such as entanglement) to test Bell's inequality, the results were in agreement with quantum theory and not local hidden variables. And the same agreement with quantum theory was obtained even when the entangled states had become separated by kilometer sized distances.

 

The fact that the results were not affected by distance, doesn't this, ironically, suggest that quantum theory is not the explanation?

 

Rather than support quantum entanglement, shouldn't such results suggest that the explanation - by some means - is through 'local hidden variables'? Since a local hidden variable explanation would not be affected by distance. Despite the conclusion of Bell's inequalities that that explanation must be logically invalid.

[Delta1212]

So despite the evidence that it is impossible for it to be the result of local hidden variables, you think it must be local hidden variables?

 

You're essentially saying that the fact that quantum entanglement isn't affected by distance proves that it can't be non-local, which doesn't make any sense.

[robinpike]

So despite the evidence that it is impossible for it to be the result of local hidden variables, you think it must be local hidden variables?

 

You're essentially saying that the fact that quantum entanglement isn't affected by distance proves that it can't be non-local, which doesn't make any sense.

 

Erm, no? I'm saying the opposite...

 

Despite the logical argument saying that local hidden variables cannot be the answer, the physical evidence suggests otherwise.

[imatfaal]

 

Erm, no? I'm saying the opposite...

 

Despite the logical argument saying that local hidden variables cannot be the answer, the physical evidence suggests otherwise.

 

Quite the opposite - we do experiments that would give one answer if there were local hidden variables and a different answer if there were entanglement. The observations show much more likely entanglement - or some other essentially non-local effect. There are still tiny lacunae which means that the possibility space of local hidden variables is not completely, utterly, once and for all, and no-returns closed out - but the overwhelming likelihood is non-locality.

 

It is odd; live with it - but use the maths and get right answers so we will worry about interpretations and deeper insight when more empirical info is available. The balance of evidence at present is fairly clear - when we get new empirical observations that may change. But the endless speculation that something must be wrong due to your gut-feeling, einstein's uneasiness etc is worthless - we go with the preponderance of evidence

[Strange]

When Alain Aspect in 1982 (and others since and before) performed quantum mechanical experiments (such as entanglement) to test Bell's inequality, the results were in agreement with quantum theory and not local hidden variables. And the same agreement with quantum theory was obtained even when the entangled states had become separated by kilometer sized distances.

 

The fact that the results were not affected by distance, doesn't this, ironically, suggest that quantum theory is not the explanation?

 

Not really, after all that is what is predicted by quantum theory (non locality).

 

 

Rather than support quantum entanglement, shouldn't such results suggest that the explanation - by some means - is through 'local hidden variables'? Since a local hidden variable explanation would not be affected by distance. Despite the conclusion of Bell's inequalities that that explanation must be logically invalid.

 

A "local" [hidden] variable is one that is limited by the speed of light (that is what "local" means). So local hidden variables would be affected by distance.

[robinpike]

 

Not really, after all that is what is predicted by quantum theory (non locality).

 

 

A "local" [hidden] variable is one that is limited by the speed of light (that is what "local" means). So local hidden variables would be affected by distance.

 

Ah yep, thank you Strange and Imatfaal - so that wasn't a very good start by me then!

 

So starting again...

 

The fact that the experimental results for entanglement are not affected by distance, doesn't this suggest that there is no entangled state. That at the point of creation, the particles are already set in their states, as then distance becomes irrelevant?

 

Does such a result raise any concerns as to the validity of quantum entanglement as the explanation?

[Delta1212]

It is either evidence for local hidden variables or for quantum entanglement being a non-local effect.

 

The evidence points toward it being a non-local effect and not being local hidden variables.

 

We go where the evidence points, not where we think it would have made more sense for the evidence to point.

[Strange]

That at the point of creation, the particles are already set in their states, as then distance becomes irrelevant?

 

That is the sort of "hidden variable" that is shown not to be possible. What Bell's inequality rules out is locally realistic variables: i.e. it cannot be limited to the speed of light (local) and it cannot be fixed, even if unknown (realistic).

[robinpike]

It is either evidence for local hidden variables or for quantum entanglement being a non-local effect.

 

The evidence points toward it being a non-local effect and not being local hidden variables.

 

We go where the evidence points, not where we think it would have made more sense for the evidence to point.

 

Yes that is sensible. So the evidence of the end result supports quantum entanglement as 'what is being measured' agrees with what was predicted. But did that prediction mention anything about distance?

 

So my question - or concern - is around that, the results being unaffected by distance.

 

My understanding of quantum mechanics / entanglement is limited.

 

First, just out of interest... Did the theory of quantum mechanics predict that entanglement will be unaffected by distance? Or is it the case that the initial theory made no judgement / statement about distance, it was initially unknown, and the theory has been updated to agree with experimental fact by including it as a principle of the theory?

 

Does quantum mechanics now have a mechanism as to why distance has no relevance to the outcome of the experiment?

 

If not, i.e. the mechanism is still unknown, is there any surprise (as a general consensus of the physics community), that distance has no relevance to the outcome of the experiment?

 

Thanks

Edited June 17, 2016 by robinpike

[Strange]

Did the theory of quantum mechanics predict that entanglement will be unaffected by distance?

 

 

Yes, that was why EPR thought it must be a flaw in the theory.

 

 

 

Does quantum mechanics now have a mechanism as to why distance has no relevance to the outcome of the experiment?

 

The fact that quantum mechanics is non-local is the mechanism.

[Enthalpy]

Hidden variables were refuted by other experiments. They are not refuted by Aspect's experiment, which only compares distances and times between the detectors.

 

The kind of experiment refuting hidden variables is that you see a correlation both with linear and with circular detectors of photon polarizations. If the photon pair decided its linear polarization at emission, the circular detectors wouldn't see a corelation, and if the photons decided their circular polarization at emission, the linear detectors wouldn't see a correlation.