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Quantum Teleportation Sends Information 143 Kilometers
SchrodingerZ writes "Scientists from around the world have collaborated to achieve quantum teleportation over 143 kilometers in free space. Quantum information was sent between the Canary Islands of La Palma and Tenerife. Quantum teleportation is not how it is made out in Star Trek, though. Instead of sending an object (in this case a photon) from one location to another; the information of its quantum state is sent, making a photon on the other end look identical to the original. 'Teleportation across 143 kilometres is a crucial milestone in this research, since that is roughly the minimum distance between the ground and orbiting satellites.' It is the hope of the research team that this experiment will lead to commercial use of quantum teleportation to interact with satellites and ground stations. This will increase the efficiency of satellite communication and help with the expansion of quantum internet usage. The full paper on the experiment can be found [note: abstract only, full article paywalled] in the journal Nature."
I'll try.
If two events are "time like" then one event occurs before the other *in*all*reference*frames*. i.e. the earlier event could cause the later event. Note that being time like doesn't require the two events to be causally linked but if A causes B then events A and B will be time like
If two events are "space like" then they cannot be causally linked because it is impossible for a signal traveling at the speed of light to get from the first event to the second event in the available time. It also turns out that for space like events different inertial observers don't even agree on which event occurred first. But this causes no problems because events C and D are not causally linked.
If an observer can travel faster than light then the above no longer holds. An observer traveling faster than light will no longer necessarily agree that A happens before B even if A causes B. An appropriate observer can wait for B to happen and then stop A from happening even though it was A that caused B. It is this paradox that leads physicists to assume that faster than light communication is impossible.
The idea of a maximum speed isn't really that crazy anyway. There are only two possible universes, one where there is a maximum speed - which implied time dilation and everything else we see in special relativity - and one where there is no maximum speed - which you get if you take the limit as c approaches infinity in the special relativity equations and turns out to be the newtonian universe. If there is no maximum speed then there is universal time and therefore all events can be uniquely assigned a time and all observers will agree on the ordering.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
It's mathematically proven that if our current understanding of quantum mechanics is correct that quantum teleportation does not allow faster than light communication. That's not the quite the same thing.
It is the hope of the research team that this experiment will lead to commercial use of quantum teleportation to interact with satellites and ground stations. This will increase the efficiency of satellite communication...
You can't send information via quantum teleportation, so exactly how do they plan to use it in satellite communication?