4 ms·

Quantum information teleported between distant atoms

18 points by dhimes 18y ago

grandalf 18y ago
how fast does the information get transmitted? Is it instant or at the speed of light?
- pmjordan 18y ago
  There still seems to be a bit of an argument about this, but the prevaling view appears to be that no actual information is being transmitted as such, so the question is nonsensical. (you cannot influence or predict to which state the wavefunction will collapse without changing the wavefunction) But to answer what you meant to ask, the wavefunction collapse is believed to be instantaneous in the entangled systems. See also: http://en.wikipedia.org/wiki/Quantum_entanglement http://en.wikipedia.org/wiki/Quantum_entanglement I know the article mentions that entanglement of atoms will allow transfer of quantum information, but I'm ashamed to say that despite my physics degree I can't figure out how they're going to transfer, say, the result of a quantum computation onto an already-entangled atom without breaking the entanglement link. (university was the last time I looked at any QM though, so I'm a bit rusty on the specifics) Maybe they mean doing so during the entanglement process, in which case the benefit is that you now have two particles holding the wave function of the result (or rather a related one holding the same information), and being atoms, they could represent the quantum equivalent of mass storage. I think it's safe to say they're well over a decade away from that, though.
- davidmathers 18y ago
  No information is transmitted. It's like this with every article about entanglement. If I have a red chip and a black chip and I mail one to you and one to your friend in New York then as soon you open your envelope and see a red chip the information "the envelope in New York contains a black chip" will be "teleported" from New York to your brain. Or not.
  - davidmathers 18y ago
    Here's a great interview I linked to last time there was an entanglement article on HN: http://www.signandsight.com/features/614.html http://www.signandsight.com/features/614.html And Eliezer Yudkowsky linked to his own explanation: http://www.overcomingbias.com/2008/05/spooky-action-a.html http://www.overcomingbias.com/2008/05/spooky-action-a.html The HN item was: http://news.ycombinator.com/item?id=276058 http://news.ycombinator.com/item?id=276058
    - captainobvious 18y ago
      Uhh doesn't Eliezer Yudkowsky's account explicitly discount the envelope explanation?
      - davidmathers 18y ago
        That was a metaphor not an explanation. What's actually happening is pretty much incomprehensible, but is just as unrelated to the transmission of information as my metaphor.
        Eliezer 18y ago
        What gets "teleported" is indexical information, information about which Everett branch "you" happen to be in. One might say that you are in the envelope - different versions of you in different envelopes. It may sound odd, but it makes a whole lot of completely unphysical behavior in the "collapse" "theory" evaporate in a puff of smoke.
- RK 18y ago
  The teleportation requires a classical, light speed signal to instruct the information recipients which type of measurement to perform. http://en.wikipedia.org/wiki/Quantum_teleportation http://en.wikipedia.org/wiki/Quantum_teleportation michael_nielsen is really the guy to ask. He "wrote the book": http://books.google.com/books?id=66TgFp2YqrAC&dq=Nielsen+Chuang http://books.google.com/books?id=66TgFp2YqrAC&dq=Nielsen...

18 points by dhimes 18y ago

grandalf 18y ago

how fast does the information get transmitted? Is it instant or at the speed of light?

pmjordan 18y ago
There still seems to be a bit of an argument about this, but the prevaling view appears to be that no actual information is being transmitted as such, so the question is nonsensical. (you cannot influence or predict to which state the wavefunction will collapse without changing the wavefunction) But to answer what you meant to ask, the wavefunction collapse is believed to be instantaneous in the entangled systems. See also: http://en.wikipedia.org/wiki/Quantum_entanglement http://en.wikipedia.org/wiki/Quantum_entanglement I know the article mentions that entanglement of atoms will allow transfer of quantum information, but I'm ashamed to say that despite my physics degree I can't figure out how they're going to transfer, say, the result of a quantum computation onto an already-entangled atom without breaking the entanglement link. (university was the last time I looked at any QM though, so I'm a bit rusty on the specifics) Maybe they mean doing so during the entanglement process, in which case the benefit is that you now have two particles holding the wave function of the result (or rather a related one holding the same information), and being atoms, they could represent the quantum equivalent of mass storage. I think it's safe to say they're well over a decade away from that, though.
davidmathers 18y ago
No information is transmitted. It's like this with every article about entanglement. If I have a red chip and a black chip and I mail one to you and one to your friend in New York then as soon you open your envelope and see a red chip the information "the envelope in New York contains a black chip" will be "teleported" from New York to your brain. Or not.
- davidmathers 18y ago
  Here's a great interview I linked to last time there was an entanglement article on HN: http://www.signandsight.com/features/614.html http://www.signandsight.com/features/614.html And Eliezer Yudkowsky linked to his own explanation: http://www.overcomingbias.com/2008/05/spooky-action-a.html http://www.overcomingbias.com/2008/05/spooky-action-a.html The HN item was: http://news.ycombinator.com/item?id=276058 http://news.ycombinator.com/item?id=276058
  - captainobvious 18y ago
    Uhh doesn't Eliezer Yudkowsky's account explicitly discount the envelope explanation?
    - davidmathers 18y ago
      That was a metaphor not an explanation. What's actually happening is pretty much incomprehensible, but is just as unrelated to the transmission of information as my metaphor.
      - Eliezer 18y ago
        What gets "teleported" is indexical information, information about which Everett branch "you" happen to be in. One might say that you are in the envelope - different versions of you in different envelopes. It may sound odd, but it makes a whole lot of completely unphysical behavior in the "collapse" "theory" evaporate in a puff of smoke.
RK 18y ago
The teleportation requires a classical, light speed signal to instruct the information recipients which type of measurement to perform. http://en.wikipedia.org/wiki/Quantum_teleportation http://en.wikipedia.org/wiki/Quantum_teleportation michael_nielsen is really the guy to ask. He "wrote the book": http://books.google.com/books?id=66TgFp2YqrAC&dq=Nielsen+Chuang http://books.google.com/books?id=66TgFp2YqrAC&dq=Nielsen...