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You've compounded their lazy science reporting by making quite a few mistakes yourself in your description: 1. There is no duplication or copying of informatio

You've compounded their lazy science reporting by making quite a few mistakes yourself in your description: 1. There is no duplication or copying of information, the original particle's state is destroyed. Copying is impossible when dealing with general quantum states[1]. (You may be thinking of measuring an entangled pair to randomly produce a stream of classical bits on each side that is the precise inverse of what is produced on the other side. This is not quantum teleportation.) 2. There is a very real notion of teleportation here, in that you take a particle with a quantum state A, and manipulate it in such a way that it stays where it is while causing a particle of the same type in a different place to be in precisely the state A, without actually moving the first particle to the second location. Yes, it's not likely to ever be used to beam anybody anywhere, but for photons it's very much like teleportation. 3. The two particles are not "literally the same", or even figuratively the same. The particles when measured will result in the other particle ending up in the opposite of the measured state, and this inversion persists even if we do operations that preserve the quantum state. [1]: https://en.wikipedia.org/wiki/No-cloning_theorem https://en.wikipedia.org/wiki/No-cloning_theorem

TheRealPomax 10y ago
"Duplication" was the wrong term, I should have said "destructive-read/write", which I did in another comment. 2. There is no teleportation in the common man, sci-fi interpretation. In order to effect the information transferral we need three times as many particles as we're transferring the information of. Per particle whose state is to be tranferred, we need two entangled particles and a target particle. To translate that to the "teleporting a thing" case, if you were to teleport a cake, you'd need a cake, two (entangled) cake-equivalent mass collections, and a target "generic particle collection" to be turned into "your cake" after running the QT algorithm. It's only teleportation if you pretend that triplicate wasted-once-used mass isn't there, which we can't do: it's there, and this is QT, not 'regular' teleportation (ignoring the fact that there is no such thing outside of works of fiction =) 3. fair enough, I simplified that the wrong way. https://en.wikipedia.org/wiki/Quantum_entanglement https://en.wikipedia.org/wiki/Quantum_entanglement and https://en.wikipedia.org/wiki/Quantum_entanglement#Applications https://en.wikipedia.org/wiki/Quantum_entanglement#Applicati... might work better as highlighting links here, although something like "Quantum Computation and Quantum Information" by Nielsen and Chuang would be a much better reference.
- adamsea 10y ago
  What common sci-fi man?
bduerst 10y ago
> The particles when measured will result in the other particle ending up in the opposite of the measured state, and this inversion persists even if we do operations that preserve the quantum state. This is the part that I don't get - what's the physics mechanism behind this? It sounds very Schrodinger's cat. It also sounds like a great way to tell if your information has been unknowingly accessed when it's travelling between two supposedly secure locations.
- johncolanduoni 10y ago
  Outside of the realm of speculative theories about how measurement works (none of which have managed to really shed any light on the matter yet), there's not much known here other than "that's what happens when you use the prescribed rules for measuring a quantum system on a particular quantum state we call entangled." I promise if we ever get a concrete answer to that question it'll get posted to HN shortly thereafter XD. > It also sounds like a great way to tell if your information has been unknowingly accessed when it's travelling between two supposedly secure locations. That's actually one of the currently possible applications of quantum mechanics to cryptography[1]. There are already multiple commercial implementations! [1]: https://en.wikipedia.org/wiki/Quantum_key_distribution https://en.wikipedia.org/wiki/Quantum_key_distribution
dave_sullivan 10y ago
It's still the consensus that we can't (even theoretically) send a bit of information this way, right? Like, no quantum telegraph? So we measure the particles and find that they are in inverse states. I assume there's a reason for this, but why are we sure that we're not just reading off a random number generator that's set from the same seed?
- johncolanduoni 10y ago
  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.
  - trentlott 10y ago
    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.
    - johncolanduoni 10y ago
      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).
      - mratzloff 10y ago

TheRealPomax 10y ago

"Duplication" was the wrong term, I should have said "destructive-read/write", which I did in another comment. 2. There is no teleportation in the common man, sci-fi interpretation. In order to effect the information transferral we need three times as many particles as we're transferring the information of. Per particle whose state is to be tranferred, we need two entangled particles and a target particle. To translate that to the "teleporting a thing" case, if you were to teleport a cake, you'd need a cake, two (entangled) cake-equivalent mass collections, and a target "generic particle collection" to be turned into "your cake" after running the QT algorithm. It's only teleportation if you pretend that triplicate wasted-once-used mass isn't there, which we can't do: it's there, and this is QT, not 'regular' teleportation (ignoring the fact that there is no such thing outside of works of fiction =) 3. fair enough, I simplified that the wrong way. https://en.wikipedia.org/wiki/Quantum_entanglement https://en.wikipedia.org/wiki/Quantum_entanglement and https://en.wikipedia.org/wiki/Quantum_entanglement#Applications https://en.wikipedia.org/wiki/Quantum_entanglement#Applicati... might work better as highlighting links here, although something like "Quantum Computation and Quantum Information" by Nielsen and Chuang would be a much better reference.

adamsea 10y ago
What common sci-fi man?

bduerst 10y ago

> The particles when measured will result in the other particle ending up in the opposite of the measured state, and this inversion persists even if we do operations that preserve the quantum state. This is the part that I don't get - what's the physics mechanism behind this? It sounds very Schrodinger's cat. It also sounds like a great way to tell if your information has been unknowingly accessed when it's travelling between two supposedly secure locations.

johncolanduoni 10y ago
Outside of the realm of speculative theories about how measurement works (none of which have managed to really shed any light on the matter yet), there's not much known here other than "that's what happens when you use the prescribed rules for measuring a quantum system on a particular quantum state we call entangled." I promise if we ever get a concrete answer to that question it'll get posted to HN shortly thereafter XD. > It also sounds like a great way to tell if your information has been unknowingly accessed when it's travelling between two supposedly secure locations. That's actually one of the currently possible applications of quantum mechanics to cryptography[1]. There are already multiple commercial implementations! [1]: https://en.wikipedia.org/wiki/Quantum_key_distribution https://en.wikipedia.org/wiki/Quantum_key_distribution

dave_sullivan 10y ago

It's still the consensus that we can't (even theoretically) send a bit of information this way, right? Like, no quantum telegraph? So we measure the particles and find that they are in inverse states. I assume there's a reason for this, but why are we sure that we're not just reading off a random number generator that's set from the same seed?

johncolanduoni 10y ago
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.
- trentlott 10y ago
  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.
  - johncolanduoni 10y ago
    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).
    - mratzloff 10y ago