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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).
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".
I doubt the extra 400km you get from doing it on the ISS is the point, because picking two points on the earth's surface that are opposite each other would be 12740km apart so the extra 3% is hardly significant.
Probably of more interest is that the ISS is doing an average speed of around 27,800 km/h which is sufficient for relativistic effects to noticeably come into play. In addition the ISS is in a different frame of reference to anything on the ground. These factors are much more interesting than the extra distance.
Very few scientific advances have been made without a few Unforeseen Consequences, but that's no reason for Apprehension or Questionable Ethics so we may just need to Forget About Freeman.
Can someone please explain to me why this can't be used for instantaneous communication purposes?
QE is rather like being married. You know that whatever you decide, your partner will want to do the opposite. However, no actual communication is involved.
Basic explanation. So I have two entangled particles, and we move them apart so you have one and I have one. At this point we have no idea what the spin on either of them is, in fact it is not determined till we try and measure it, but they must be different. I now measure the spin on mine and find it is +1, meaning yours is -1 "instantly". You can now measure the spin on yours to confirm that.
The problem is because the spin of the particle is undetermined until I read it and when I do read it the result will be random, there is no way to transmit any useful information.
Not yet. anyway. Someone will borrow another sci fi concept and magically make it work.
No they won't. There is a certain cult that treats science as a religion and refuses to understand that there are basic laws of physics that constrain us. FTL communication causes a litany of paradoxes and trying to turn quantum entanglement into a FTL communication device shows a fundamental lack of understanding of what is going on.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
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.