Researchers quantum teleport particle of light six kilometres

Re:Researchers quantum teleport particle of light six kilome... by johncolanduoni on Wednesday September 21, 2016 @06:56PM (#12553006)

Quantum teleportation is actually kind of the opposite. You transmit a quantum state (which if your particle is as simple as a photon, can be used to create a copy of the particle) by using an already-separated entangled pair and sending two classical bits any boring old way (fiber, wire, smoke signals).

If you don't get the classical information on the receiving end, any attempts to read the quantum state will garble the quantum transmission such that it'll be indistinguishable from random noise. Since those classical bits are limited by the speed of light, so is the overall transmission of the state.

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Re:Researchers quantum teleport particle of light six kilome... by trentlott on Wednesday September 21, 2016 @07:46PM (#12553253)

So why does the reciver need the two bits?

I'm not prone to study too deeply because I've learned (apparently) very bad analogies or schemes for entanglement.

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Re:Researchers quantum teleport particle of light six kilome... by johncolanduoni on Wednesday September 21, 2016 @08:00PM (#12553315)

The teleportation process involves using a measurement to entangle the receiver's side of the pair with the original state in a useful way. Since measurements are probabilistic (and the measurement is along two qubits) there are four outcomes of this measurement with four different kinds of "garbling" of the transmission (one of which is no garbling).

The receiver needs the two bits to choose which of four kinds of garbling occurred, so it can correct them with the appropriate post-processing (if necessary).

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Re:Researchers quantum teleport particle of light six kilome... by mratzloff on Wednesday September 21, 2016 @08:54PM (#12553514)

So it's kind of like a traditional error-correcting code, just sent along a separate channel?

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Re:Researchers quantum teleport particle of light six kilome... by johncolanduoni on Wednesday September 21, 2016 @09:31PM (#12553672)

Sort of. The only issue with that interpretation is that either piece of data in isolation conveys none of the original information, even probabilistically. A better analogy would be sending two classical bits by different channels, with the desired bit being the XOR of the two, and one of the bits being chosen by a random number generator.

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