Quantum Entanglement - proven?

In summary, quantum entanglement has no maximum distance limit and has been proven through various experiments. However, there are still loopholes and debates surrounding its existence. It is a fundamental aspect of quantum mechanics that allows for continuous transformations between pure states and cannot be explained by standard probability theory.
  • #1
Ward
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Hi,

I have some general questions on Quantum Entanglement?

1. Is there a maximum distance between the two objects before it does not work?
2. Has it actually been proven/tested? If so can anybody provide some further information on this?

Thanks,

Ward
 
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  • #2
Hi
Ward said:
1. Is there a maximum distance between the two objects before it does not work?
No!

Ward said:
2. Has it actually been proven/tested? If so can anybody provide some further information on this?
Yes. Its being used in laboratories for testing different things.

Take a look at here.
 
  • #4
Remember all experiments to date haven't closed all the loopholes in one experiment; rather they have been closed in separate experiments (leaving open one or two of the other loopholes). Although I believe entanglement (non-local reality) does truly exist, these loopholes leave open the possibility of local reality - http://en.wikipedia.org/wiki/Loopholes_in_Bell_test_experiments
 
  • #5
Ward said:
Is there a maximum distance between the two objects before it does not work?
Not only is there no maximum distance but it has been argued that barring loopholes, if the non-local effects observed in Bell-type experiments propagate at any finite speed, then non-locality could be exploited for superluminal communication:
The new hidden influence inequality shows that the get-out won't work when it comes to quantum predictions. To derive their inequality, which sets up a measurement of entanglement between four particles, the researchers considered what behaviours are possible for four particles that are connected by influences that stay hidden and that travel at some arbitrary finite speed. Mathematically (and mind-bogglingly), these constraints define an 80-dimensional object. The testable hidden influence inequality is the boundary of the shadow this 80-dimensional shape casts in 44 dimensions. The researchers showed that quantum predictions can lie outside this boundary, which means they are going against one of the assumptions. Outside the boundary, either the influences can't stay hidden, or they must have infinite speed.
Quantum non-locality based on finite-speed causal influences leads to superluminal signalling
http://www.nature.com/nphys/journal/v8/n12/full/nphys2460.html
http://arxiv.org/pdf/1110.3795v1.pdf
 
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  • #6
StevieTNZ said:
Remember all experiments to date haven't closed all the loopholes in one experiment; rather they have been closed in separate experiments (leaving open one or two of the other loopholes). Although I believe entanglement (non-local reality) does truly exist, these loopholes leave open the possibility of local reality - http://en.wikipedia.org/wiki/Loopholes_in_Bell_test_experiments

I think of it a bit differently, using "proven" in two different senses. I would say that entanglement as a prediction of quantum mechanics has been "proven" in the same sense as the frame invariance of the speed of light as a prediction of relativistic quantum electrodynamics has been "proven". Here "proven" means that non-trivial predictions of the theory have been tested, and the theory has successfully predicted all results to date. "Proven" does not mean that the theory will not be falsified by future observations. The Bell tests are the most spectacular examples of entanglement, but things like the superconducting ground state and the fractional quantum hall state are also examples of entanglement.

Nonlocality, on the other hand is about accounting for experimental results independently of quantum mechanics, taking into account all possible theories beyond quantum mechanics. The spirit here is different and stricter, because the Bell inequalities are derived independently of quantum mechanics. Because I feel that here one should use a stricter notion of "proven", I would say nonlocality can never be proven, so here one typically tries to be precise by stating a null hypothesis, and stating p values.

Here's a talk by Subir Sachdev about current research on entanglement in high temperature superconductivity.
 
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  • #7
Ward said:
Has it actually been proven/tested? If so can anybody provide some further information on this?

You have got some interesting answers here.

However I have got a slightly different take:
http://arxiv.org/pdf/0911.0695v1.pdf

Basically if you want to model physical processes probabilistically you have two choices - standard probability theory and QM.

What separates the two is one allows entanglement and the other doesn't - only QM allows entanglement. The other thing is only QM allows continuous transformations between pure states which is really required for physical processes. If a transformation can be applied for a second it can be applied for half a second an so on. So it turns out if you want this very reasonable requirement, and its hard to see how it can be done without, then you get entanglement.

Thanks
Bill
 
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  • #8
bhobba said:
However I have got a slightly different take:
http://arxiv.org/pdf/0911.0695v1.pdf
This one seems better than the previous papers where QM was merely a kind of probability theory!
The idea of pushing QM to become only a mathematical theory applied to the universe is too bold to be successful (also I don't like it:D), but this paper seems to take an appropriate compromise.
 

1. What is quantum entanglement?

Quantum entanglement is a phenomenon in which two or more particles become connected in such a way that the state of one particle affects the state of the other, even when they are separated by a large distance.

2. How is quantum entanglement proven?

Quantum entanglement has been proven through various experiments, such as the Bell test, which demonstrates that the correlations between entangled particles cannot be explained by classical physics.

3. What is the significance of quantum entanglement?

Quantum entanglement is significant because it allows for instantaneous communication and information sharing between particles, which has potential applications in quantum computing and cryptography.

4. Can quantum entanglement be used for faster-than-light communication?

No, while quantum entanglement allows for instantaneous communication between particles, it does not violate the speed of light limit or allow for communication to occur faster than the speed of light.

5. Is quantum entanglement a proven theory or just a hypothesis?

Quantum entanglement is a proven phenomenon that has been extensively studied and confirmed through numerous experiments. However, there is ongoing research and debate surrounding its full understanding and implications.

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