This question comes from someone who is interested in Physics but with no theoretical background.
In 1936, EPR presented the thought experiment which later came to be known and quantum entanglement.
I understand that the thought experiment reflects the bizarre conclusions of quantum theory, i.e. observation of a state of a particle at one place would let that observer know the state of the correlated particle (light years away) even without observing it. And since quantum theory says that the state of a particle is always in a fuzzy state unless you observe it, this implies that the other particle is getting affected without even observing it…… hence spooky action at a distance …… which doesn't quite fit with traditional Newtonian physics.
The EPR theory as a thought experiment is quite understandable to me.
What I do not understand is, why did scientists, decades later, build tunnels of several kilometers and sent two entangled particles to each end, and then measure the state of those particles to ascertain quantum entanglement.
I mean, what were they expecting —– were they expecting the states of the particles to be not in co-relation? How would they explain for that?
As far as I have understood the EPR experiment was a thought experiment that kind of throws quantum theory in an uncomfortable position. But its an experiment that cannot be disproven —- co-relates are co-relates. It just puts the philosophy of quantum mechanics to doubt.
And you cannot communicate information through entanglement anyway. So my question again : why the experiments?
PS : Please, if possible, provide me with relevant links to learn more about this topic. I don't trust random blogs on the net, and the Wikipedia article is just difficult to understand.
Best Answer
Even for things that seem very clear from the theory, you will want to check them. You asked
Well, of course they were expecting the entanglement. But finding that this is NOT there, would have been a huge thing - Quantum Mechanics needed to be amended!! As much sense as a theory might make, it must be subject to experimental verification in all aspects.
Similarly, most physicists were convinced for decades that the Higgs boson must be there and still we build ever larger experiments looking for it, since if we had NOT found the Higgs boson, we would have to re-think a large bit of what we know about particle physics.