I've been keenly following this area of research and have heard some of the talks and read some papers. I concur with the sketch given by @gaze.
1. The notion of unitarity is a "common sense" rule that implies that you can consistently assign probabilities to possible outcomes in a quantum mechanical experiment (http://en.wikipedia.org/wiki/Unitarity_%28physics%29)
2. The notion of locality states that what happens on Jupiter better not affect how fast your code compiles this morning (or how experiments run on earth). This is an important postulate, because if this weren't true, we might as well give up on doing science as there would be arbitrarily many external influences we couldn't take into account.
All our experiments so far are perfectly consistent with these two principles. Quantum field theory is the brainchild of the marriage of unitarity (from quantum mechanics) and the idea of locality (in field theory). Our world view today ("Standard model of particle physics") is based on this.
In practice, calculating answers using this theory is painfully difficult. YOu will add up thousand pages worth of algebraic terms and then your answer will 'miraculously' reduce to a few terms. This and other observations have inspired researchers to search for underlying structure... leading to what is now being called the 'amplitude revolution' by some people.
> 2. The notion of locality states that what happens on Jupiter better not affect how fast your code compiles this morning (or how experiments run on earth). This is an important postulate, because if this weren't true, we might as well give up on doing science as there would be arbitrarily many external influences we couldn't take into account.
Unfortunately for science, the principle of locality has been violated multiple times with experiments involving quantum entanglement.[1]
I think you are confusing Micro-causality with Einsteinian locality[2], the theory that influences propagate at most as fast as light. Micro-causality is the locality that's associated with quantum field theory and what was discussed in this article. Many theories in the history of science have been proven wrong. And if one of these is, then it will no lead to the end of science as we know it.
I bet my arm that in a Many World Interpretation of Quantum mechanics, those apparent non-localities have not, in fact, have been violated.
We can have a classical analogy to this. Put a blue ball and a red ball in a black box. Shake the box. Without looking, take a ball from the box and put it in a black safe. That way, you should have no idea which ball in in the safe.
Now send the black box to your colleagues on Mars, along with a copy of your experimental protocol. Let them open the box. And, lo and behold, the instant they see the ball, they know which colour your ball is, despite the fact you're separated by several light-minutes. As if information travelled faster than light —no, scrap that, instantaneously.
Quite underwhelming, isn't it? Well, the EPR though (and actual) experiments work on similar principles: there is a common cause. When 2 particles are entangled, it means they share information. When you send those particles away in opposite directions, they carry this information with them, at Slower Than Light speed. Then we perform some experiment on one of the two particles, and we know instantly how some other experiment is likely to turn out with the other particle.
It's that mundane. It only gets confusing when you talk of "probabilities", instead of talking of the square of complex amplitudes… which are a bit different from actual probabilities. In the Copenhagen interpretation of quantum mechanics, we tend to think of the universe as unique, and the laws of physics have some fundamental randomness in them. The Many World interpretation is simpler: no randomness, just a universe that splits in multiple blobs that eventually cease to interact with each other (The split is not instantaneous: it propagates at the speed of light at most).
So, when you perform that experiment with the first particle, you're not telling the second one how to behave. You merely learn which universe you are living in.
---
Now, find a reliably replicated experiment where information was transmitted faster than light, and I will be choking through sheer astonishment.
The way I see it, locality in every Lorentz frame = causality.
What Bell experiments disprove is local realism. In the conventional formulation of quantum physics (quantum mechanics, quantum field theory, etc.) it's realism that takes the fall. Locality is still crucial in the conventional perspective.
Are the terms they reduce to constant, i.e. are they the same variables like spin or charge, no matter the problem? I'm not a physicist - not even close - but I do love a good mathematically general abstraction across a problem space.
1. The notion of unitarity is a "common sense" rule that implies that you can consistently assign probabilities to possible outcomes in a quantum mechanical experiment (http://en.wikipedia.org/wiki/Unitarity_%28physics%29)
2. The notion of locality states that what happens on Jupiter better not affect how fast your code compiles this morning (or how experiments run on earth). This is an important postulate, because if this weren't true, we might as well give up on doing science as there would be arbitrarily many external influences we couldn't take into account.
All our experiments so far are perfectly consistent with these two principles. Quantum field theory is the brainchild of the marriage of unitarity (from quantum mechanics) and the idea of locality (in field theory). Our world view today ("Standard model of particle physics") is based on this.
In practice, calculating answers using this theory is painfully difficult. YOu will add up thousand pages worth of algebraic terms and then your answer will 'miraculously' reduce to a few terms. This and other observations have inspired researchers to search for underlying structure... leading to what is now being called the 'amplitude revolution' by some people.