Bubble Boy wrote:I thought quantum physics like this particular example meant distance wasn't a factor? I was under the impression one of the key attractions for this type of research was that it could provide instantaneous communications not limited by distance. Like someone else mentioned previously, possibilities like real time control over a Mars rover and such.
Right, that's what I was gathering the implication to be. Problem is, something like that still violates relativity (or can, anyway) as far as I understand it (which isn't very far, admittedly).
QT does not allow FTL transmission of information.
When a set of particles is A entangled with set B, and one takes a reading of the quantum properties of one set, one immediately knows the properties of the other regardless of distance. However, the readings are randomized, so one cannot use it for communication.
Unless one further entangles set A with a "message" to form a compound signal, and transmits this; the message can be extracted from the compound signal using B. Only, the signal moves at c. You need B to extract the initial message or it is impossible to read.
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Quantum teleportation involves the measurement of a photon, transmission of the result of that measurement, and some tweaking with an entangled particles during and after the measurement to reproduce the quantum state of the originally measured particle. It's easy to see that there will be no instantaneous communication because of the intermediate step; the reason QT is significant at all is because the classically transmitted measurement data does not encompass the original quantum state of the measured particle (nor can it).
Invictus ChiKen wrote:Okay so if I get this right....
We now have a very fancy long range modem right?
Or, rather, as I've been following for the last several years as they perfect this stuff, they are moving closer to a perfect way of transmitting data without interception and decryption being a problem. Unless you have the key already or are part of the network, you cannot read the signal without it being complete nonsense.
-- Asuka
