Quantum entanglement of a single particle has been observed by researchers

In these types of quantum reality-probing experiments, any problems of experimental design that affect the validity of the findings are referred to as loopholes, as though there's some awkward legal wrangling going on, because the experiments were conceived originally to determine whether the controversial Bell's inequalities hold. The inequalities were designed to test Bell's theorem which states that any hidden variables (things not yet observed that have a causal influence on experimental outcome) are required to be non-local if they are to hold with the predictions of quantum mechanics. Non-local here means 'spooky action at a distance'.

Showing the inequalities to be violated (incorrect by experiment) was originally controversial because Einstein and Bohr had differing notions of what the quantum mechnical theory implied about reality. They engaged in a lengthy, open discussion about it which was never resolved. Einstein believed in local realism, in which there is no spooky action at a distance and properties like position and momentum exist even when not being measured. Bohr, on the other hand, insisted that there simply wasn't an underlying reality and that only when measurements are made are properties like position and momentum condensed out of the quantum mechanical reality. So, you see, the significance of the experiment is in line with the underlying nature of reality; by closing another loophole, we get closer to what's what.

[The rest here is historical context.]

The familiar refrain, "God does not play dice," is almost always taken out of context - within its original statement, Einstein was also talking about a kind of telepathy required with it - the non-local aspect of quantum mechanics. Einstein said in 1954 'it is not possible to get rid of the statistical character of the present quantum theory by merely adding something to the latter, without changing the fundamental concepts about the whole structure'. He was saying he lost conviction in using a hidden variable theory to replace quantum mechanics.

Bohr's view, like Einstein's later view, is more in line with modern thinking. A team led by Aspect in 1981-82 ruled out either locality or objective reality, by testing the inequalities experimentally. This left possible a non-local reality. In 2006, a group tested Leggett's inequality, and showed it to be violated, which refined experimentally what the nature of reality is, though showed only that realism and a certain type of non-locality are incompatible, without ruling out all possible non-local models. (Nature, April 2007) Aspect remarked that philosophically, the 'conclusion one draws is more a question of taste than logic'.

Current thinking is that "collapse" is a hack. We've always talked about the wavefunction collapsing but never been able to describe the onotology of collapse. Non-locality seemed for a time to explain why that is so: because collapse happened non-locally, it could happily violate the law of non-contradiction from the viewpoint of a Lorentz-invariant observer.

The alternative to collapse is decoherence due to entanglement with a heat bath. There are still unexplained issues with this, in my view, but that may simply be because I don't fully understand how the ontology of the classical world is constructed by this process, or why once that ontology is constructed the beings that are governed by its laws are only capable of being aware of the foundations via the most indirect kind of inference.

In any case, this experiment shows some of the power of "entanglement" vs "collapse" as an account of measurement. If "collapse" is a short-hand for measurements that involve "entanglement with a heat bath" then it is possible perform a measurement that involves entangling part of a wavefunction with a coherent signal (the local oscillator in a homodyne detector) without doing to it what we would call "collapse". That appears (to me at least) to be what is happening in the present case. No magic involved.

I very much like this avenue of thought, as a layperson.

I forget where I read it, fairly recently somewhere... but something along the lines of measurement == entanglement.

The idea is that you set up a stream of entangled particles and arrange it so that, for example, one stream is available at Earth at the same moment that the entangled particles are available on Mars.

Then if you somehow gain the ability to twiddle the state of one end and measure the state of the other, you can communicate instantaneously.

But the first step to doing this is to develop a brand new physics where it is actually possible. Results that confirm/refine the current understanding won't ever enable it.

>> Could you explain how this would be faster than light? Wouldn't the particles be traveling at the speed of light?

As maxerickson says, you emit streams of entangled particles from a central location heading in opposite directions. People equidistant from that location can communicate instantaneously. Alice modulates the wave function collapse by either taking a measurement or not. Say measuring indicates a 1 and non-measurement indicates a 0. Bob over at the other end uses his ability to distinguish a collapsed wave function from a non-collapsed one to get 1's and 0's out the other end. Because the measurement induced wave function collapse is instantaneous this will be faster than light communication. Bob can tell weather Alice is measuring or not, right now.

I stand by my assertion that physicists can not tell the difference. I'll also add that the reason is that there is no difference. But by all means continue to downvote without a counterexample.