There is absolutely no doubt that if the reader applies an intuitive classical interpretation of the term "state" to what physicists mean by a quantum state, then the reader will end up with some wrong impressions (and some right ones). The fact is that there are certain things that are going on that just don't map well on to normal, classical language. And this is not the readers fault; he's a normal, lay human being, and really smart people have been fighting over how to interpret the (unambiguous) experimental data for almost a century now without reaching a consensus.
Now, it would probably be better if physicists used the term "qustate" to refer to the state, and that they used this press releases, and that they said stuff like "when Alice makes her measurement, the qustate of Bob changes instantaneously". That way no one would go applying their classical intuition about what a "state" ought to be to the density matrix. Instead, they would ask "what's a 'qustate'?", and someone would say "well, it's sort of like a classical state...but it's not the same...and it's sorta like an epistemic probability distribution...but also not really...and the difference are subtle and very profound and you have to be careful and it takes a good amount of studying before you can understand." And that would be great and maybe a few more people would go actually read about it. But as it stands physicists are more than happy to allow laymen to misinterpret their terminology when it leads to their work sounding more exciting and getting more funding. There is definitely something of a Motte-and-Bailey going on. ( http://slatestarcodex.com/2014/11/03/all-in-all-another-bric... )
> On the other hand, if Bobs makes a measurement after Alice measurement, the result should "agree" with the result Alice measurements. So, has something changed?
Actually, the mere agreement of Alice and Bob's measurement doesn't really give evidence that anything on Bob's side has changed. If I jumble a blue marble and a red marble in an urn and then put them in separate brown bags and give you one at random, then when you look in your bag that will instantly determine what I'll get when I look in mine, but it didn't change anything about my bag in the normal, physical sense.
The way in which quantum mechanics differs from this situation is subtle but significant.
Yes, I think you hit the nail on the head here.
After a few curses of quantum mechanics (with the Sakurai book) and working in the field I still not sure if the press release is misleading or just wrong.
One of the important details is that Bob can't do any experiment to distinguish the photon before Alice measurement and the state of the photon after Alice measurement. If it's not possible for him to distinguish the states, has it really changed?
On the other hand, if Bobs makes a measurement after Alice measurement, the result should "agree" with the result Alice measurements. So, has something changed?
I think that the press release it's completely misleading and perhaps wrong.