6 ms·

They don't go into details, but I assume the implications for communications are new ways to make entangled particles for quantum cryptography, not FTL communic

by quux 14y ago

They don't go into details, but I assume the implications for communications are new ways to make entangled particles for quantum cryptography, not FTL communication or something else that's considered impossible. Right?

themgt 14y ago
Well, from my read, it'd be theoretically possible to transmit at near-infinite bandwidth using quantum entanglement (since you just keep adding more entangled particles). There'd still be the latency of at least the speed of light though
- adrianbg 14y ago
  Entanglement alone can't be used to transmit information. If this is the first time long-range entanglement has been possible then the communications advances they're talking about would include anything that requires parties to share entanglement over a distance. So quantum encryption, key exchange, superdense coding (is that even likely to be useful?) etc. Someone who knows what they're talking about want to weigh in here?
- fudged71 14y ago
  "In Quantum entanglement, part of the transfer happens instantaneously. Repeated experiments have verified that this works even when the measurements are performed more quickly than light could travel between the sites of measurement" http://en.wikipedia.org/wiki/Quantum_entanglement http://en.wikipedia.org/wiki/Quantum_entanglement
  - adrianbg 14y ago
    Yeah it occurs instantaneously but because you can't influence either particle without destroying the entanglement you can't use it to communicate faster than the speed of light. http://curious.astro.cornell.edu/question.php?number=612 http://curious.astro.cornell.edu/question.php?number=612
- yeison 14y ago
  Entangled particles communicate instantaneously through space. That is to say, communication faster than the speed of light. This was actually one of the reasons that Einstein did not want to accept quantum theory. In fact, he proposed quantum entanglement as an argument against the validity of quantum theory. According to quantum theory, transfer of information faster than the speed of light should be possible (via quantum entanglement). Therefore, quantum theory was incorrect/incomplete- that was Einstein's reasoning. There would still have to be an entanglement step. The photons need to be coupled. This is currently accomplished by a laser across long distances. I suppose that in this sense there is a latency at the speed of light to add new particles. But once the photons have been entangled they can communicate instantaneously.
  - iliis 14y ago
    No. Sorry to shatter the dream of FTL communication. You cannot achieve it with entangled particles. While it seems like there is some transfer of information going on its much better to think of two entangled photons as a pair of dice which will roll the same number wherever they are. Spooky, yes. Useful for cryptography, certainly. But sadly no FTL communication. At best its FTL transmission of complete noise. Edit: See http://en.m.wikipedia.org/wiki/Quantum_teleportation http://en.m.wikipedia.org/wiki/Quantum_teleportation for more. Edit 2: If you say that the particles themselve are 'communicating' ftl, then you are perfeclty correct, yes. Unfortunatly one cannot use this behaviour to transmit arbitrary data.
    - znowi 14y ago
      Ah, that's too bad. I was about to imagine future hackers who would tap into a secret FTL communication with their own particles to steal entangled data :)
    - tobias3 14y ago
      I think this was on HN recently. http://arstechnica.com/science/2012/10/quantum-entanglement-shows-that-reality-cant-be-local/ http://arstechnica.com/science/2012/10/quantum-entanglement-...
    - 14y ago

by quux 14y ago

themgt 14y ago

Well, from my read, it'd be theoretically possible to transmit at near-infinite bandwidth using quantum entanglement (since you just keep adding more entangled particles). There'd still be the latency of at least the speed of light though

adrianbg 14y ago
Entanglement alone can't be used to transmit information. If this is the first time long-range entanglement has been possible then the communications advances they're talking about would include anything that requires parties to share entanglement over a distance. So quantum encryption, key exchange, superdense coding (is that even likely to be useful?) etc. Someone who knows what they're talking about want to weigh in here?
fudged71 14y ago
"In Quantum entanglement, part of the transfer happens instantaneously. Repeated experiments have verified that this works even when the measurements are performed more quickly than light could travel between the sites of measurement" http://en.wikipedia.org/wiki/Quantum_entanglement http://en.wikipedia.org/wiki/Quantum_entanglement
- adrianbg 14y ago
  Yeah it occurs instantaneously but because you can't influence either particle without destroying the entanglement you can't use it to communicate faster than the speed of light. http://curious.astro.cornell.edu/question.php?number=612 http://curious.astro.cornell.edu/question.php?number=612
yeison 14y ago
Entangled particles communicate instantaneously through space. That is to say, communication faster than the speed of light. This was actually one of the reasons that Einstein did not want to accept quantum theory. In fact, he proposed quantum entanglement as an argument against the validity of quantum theory. According to quantum theory, transfer of information faster than the speed of light should be possible (via quantum entanglement). Therefore, quantum theory was incorrect/incomplete- that was Einstein's reasoning. There would still have to be an entanglement step. The photons need to be coupled. This is currently accomplished by a laser across long distances. I suppose that in this sense there is a latency at the speed of light to add new particles. But once the photons have been entangled they can communicate instantaneously.
- iliis 14y ago
  No. Sorry to shatter the dream of FTL communication. You cannot achieve it with entangled particles. While it seems like there is some transfer of information going on its much better to think of two entangled photons as a pair of dice which will roll the same number wherever they are. Spooky, yes. Useful for cryptography, certainly. But sadly no FTL communication. At best its FTL transmission of complete noise. Edit: See http://en.m.wikipedia.org/wiki/Quantum_teleportation http://en.m.wikipedia.org/wiki/Quantum_teleportation for more. Edit 2: If you say that the particles themselve are 'communicating' ftl, then you are perfeclty correct, yes. Unfortunatly one cannot use this behaviour to transmit arbitrary data.
  - znowi 14y ago
    Ah, that's too bad. I was about to imagine future hackers who would tap into a secret FTL communication with their own particles to steal entangled data :)
  - tobias3 14y ago
    I think this was on HN recently. http://arstechnica.com/science/2012/10/quantum-entanglement-shows-that-reality-cant-be-local/ http://arstechnica.com/science/2012/10/quantum-entanglement-...
  - 14y ago