European Researchers Propose Quantum Network Between Earth and ISS

New kalalau_kane writes with this tidbit from Extreme Tech: "A group of European researchers has proposed the largest quantum network yet: Between Earth and the International Space Station. Such a network would see entangled photons transmitted over a distance of 250 miles — two or three times greater than previous quantum communication experiments. Not only will this be the first quantum experiment in space, but it will allow the scientists to see if entanglement really is instantaneous over long distances, and whether it's affected by gravity." The proposal (licensed CC BY).

Re:10,000 times faster than the speed of light?

[UnHolier than ever]

It is instantaneous, but you can't measure zero - all you can measure is "it took less than x picoseconds" where x depends on your timer's precision, and from this infer "it went at least this fast".

Re:Oooh gravity experiment

[iggymanz]

wrong, it is actual science and the way things behave, and the equations are complete (outside of realm of heavy space-time curvature such as near black hole). It is just different from the mental model most humans have. Nothing stopping anyone from taking prerequisite basic calculus and then basic quantum mechanics course.

Re:Not Much Advantage Gained

[femtobyte]

Presumably, the ability to shoot a beam of light >250 miles, without needing to build a 250-mile-long evacuated beamline, is a major advantage gained. The Earth is surrounded by this annoying thing called "the atmosphere," which wreaks havoc with light traveling only a few miles; the faster you can get out of the atmosphere (by, e.g., shooting straight up), the easier it'll be to get any useful amount of light to the other end.

Re:Always a letdown.

[nsaspook]

Can someone please explain to me why this can't be used for instantaneous communication purposes?

Because that would require FTL transfer of energy/information.

It's like if three people were in a room and #3 put a nickle in #1's pocket and a dime in #2's pocket completely randomly. They all know there is only the possibility of a nickle or a dime but 1&2 won't know what coin until they actually look in the pocket.

#1 flies to Mars on a rocket.
#2 stays on earth and looks in his pocket. He now knows instantaneously the value of the coin in #1's pocket on Mars.

Not faster than light

[Roger W Moore]

What the article fails to point out is that actually nothing is travelling faster than light. This is the fancy equivalent of shining a bright laser on the moon and moving it around so that it appears that the bright spot on the surface moves at a velocity in excess of c. There is no problem with this because no information is transmitted from one point on the moon to another point on the moon faster than c - the only information which is transmitted is from the person pointing the laser to the moon. In the same way no data is transmitted between the two people making the measurements because neither has any control over the outcome of their measurement.