This would be interesting as a distant star would exhibit red-shift unlike something as close as our sun. So until further data such as this, we just have the single experiment. Which from my limited understanding, would give the data to draw some solid conclusions. Exciting stuff, and I could only speculate upon the results, though somebody more up upon the matter may well have some better insights.
Though it may well be a way to measure distances more accurately would be my limited take away from this. Maybe not, but certainly something going on here that will enhance our understanding of physics on all levels.
I gather this experiment somehow entangles photons from the sun with photons produced by the experimenters, but they're already here when that happens right? So how does the distance come into play. I think I'm probably looking at it too "classically".
It looks like the keyword in the title was light "sources" that are 150 Million Kilometers apart. I didn't catch that at first.
Exactly. They are testing if photons on Earth are the same as those produced in the Sun - a very simple test of the translation invariance of the laws of quantum physics.
> If you couldn't entangle them, what would that mean?
If such experiments failed despite repeated efforts, then maybe the laws of quantum physics are not invariant under translation as far as 150M kilometers.
Note that we communicate with Voyager crafts for instance using classical EM waves, so presumably the laws of classical EM work the same as far as the edge of the solar system.
To me, the surprise is that identical pairs always take the same path.
Oh no. It is definitely possible to entangle two photons from two different sources. Say two hydrogen atoms emit a photon each; then you just need a non-linear crystal to entangle them, or use linear crystals and post-select good results. Here is a recent example for the latter for quantum repeaters , though this has been done for decades now. And making two different photon sources indistinguishable (or controllably-distinguishable) is like the first thing you do in a quantum optics lab.
> I also understood entanglement...
That's not a correct way to think of entanglement. Two particles are (maximally) entangled if
(1) you do the same measurement on the two particles, the results are (perfectly) correlated.
(2) if you do orthogonal measurements on the two particles, the results are (perfectly) uncorrelated.
And all this happens in a way that no local classical theory can explain.
The important part of the paper is the first result about two-photon interference. It shows that two photons from Sun and Earth can be made indistinguishable from each other and hence show maximum interference. This is evidence for the postulate of quantum theory that all photons (or other fundamental particles) can be made identical to each other.
 that take care of all prerequisite conditions of Bell's theorem. Also called loop-hole free Bell experiments. See https://en.wikipedia.org/wiki/Bell_test_experiments#Hensen_e...