8 ms·

I wonder how long before we see major internet nodes connected via quantum entanglement.

teraflop 11y ago
Entanglement can't be used for communication. https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem
- photonic29 11y ago
  But it can be used for security: http://www.nature.com/news/2008/080827/full/news.2008.1067.html http://www.nature.com/news/2008/080827/full/news.2008.1067.h...
  - Florin_Andrei 11y ago
    Right. So connected the usual way, but using QM for security.
- igravious 11y ago
  I was going to post that link. This is the standard theory, isn't it? Most physicists subscribe to this, regardless of their interpretation of quantum mechanics (Copenhagen, De Broglie–Bohm, and so on?)
  - dogma1138 11y ago
    Yes basically if you build say 2 entangled bytes you'll basically get random data out of them every time you measure / set their state you'll basically get random data. The only way to make the data "make sense" is to share the measurements between both observers on a side channel. But and that's the big but which i don't understand and couldn't get a decent explanation from anyone who i know has some / more understanding that i do in QPT. Yes i understand if you got 2 observers Alice and Bob both of them with a pair of say you got a pair of 12 entangled quantum bytes. Bob can't tell by random measurement if Alice has done something since the state of his 12 qbytes is "random", however if the interpreted say say's Hello World! or I Just Changed It why Bob can't superimpose additional information he has such as the knowledge of the English language to interpolate that Alice actually did something. On top of that the no information theorem is also tied to the no-cloning theorem which conflicts with well with how some one would explain quantum teleportation. The explanation I managed to find is that the no-cloning and no-teleportation theorems do not prevent quantum teleportation but rather classical one which means that you cannot encode a quantum state into a classical system and then clone/teleport that information into another quantum system, but you can do it from one quantum system to another which is where my brains starts to scream. http://courses.cs.washington.edu/courses/cse599d/06wi/lecturenotes4.pdf http://courses.cs.washington.edu/courses/cse599d/06wi/lectur...
- omnipedal 11y ago
  They already teleported information via similar means, so I would hope this doesn't mean FTL communication is impossible.
  - ikeboy 11y ago
    It does mean that, actually.
    - omnipedal 11y ago
      https://en.wikipedia.org/wiki/John_G._Cramer https://en.wikipedia.org/wiki/John_G._Cramer This guy seems to believe otherwise and many other scientific breakthroughs were declared as impossible before they were done, it is unwise to cling to limiting beliefs like that as that kind of attitude prevents technological advancement. In fact, it can be speculated that messages could be sent in the future as well as in the past, and other parallel universes as well.
      - ikeboy 11y ago
        All his experiments have failed. See https://faculty.washington.edu/jcramer/NLS/NL_signal.htm https://faculty.washington.edu/jcramer/NLS/NL_signal.htm People have been trying to use QM to show FTL communication since QM was discovered, it doesn't work. >In fact, it can be speculated that messages could be sent in the future as well as in the past, and other parallel universes as well. Yes, you can speculate whatever you want, that doesn't make it any truer.
        omnipedal 11y ago
        It's only 2015, I think it's a little ridiculous to make far sweeping conclusions about whole realms of science supposedly not working based on limited current understanding of science.
        ikeboy 11y ago
        We've known about QM for 80 years. It's given accurate predictions for all that time. What exactly do you think is limited in currnt understanding of science?
- moron4hire 11y ago
  I don't understand the limitation that "neither Alice nor Bob is allowed, in any way, to affect the preparation of the initial state." Why shouldn't Alice create the initial state? If we can use the quantum entanglement to determine if some Eve has intercepted a message between Alice and Bob, then why can't we use the fact of tampering as the data pipe? Why shouldn't Alice create the initial state and Bob use the quantum entanglement to communicate back? Use two constant photon streams between the two, one from Alice to Bob, one from Bob to Alice. The photons that are emitted are identical--it's notionally a carrier wave. Alice checks to see if Bob "tampers" with the photons. The actual data encoded in the photon itself isn't important. Say I fire a laser beam to the Moon. It's going to take a second and a half to get there. I send one half of my entangled pair to the Moon and I send the other half down a fiberoptic delay line. In 1.5 seconds, I start checking whether or not my entangled photons have been tampered with, and that is the data stream back from the moon.
  - ikeboy 11y ago
    >If we can use the quantum entanglement to determine if some Eve has intercepted a message between Alice and Bob, then why can't we use the fact of tampering as the data pipe? You can't; quantum key distribution requires a classical channel as well. See https://en.wikipedia.org/wiki/Quantum_key_distribution#BB84_protocol:_Charles_H._Bennett_and_Gilles_Brassard_.281984.29 https://en.wikipedia.org/wiki/Quantum_key_distribution#BB84_... >After Bob has measured all the photons, he communicates with Alice over the public classical channel. Edit: also, "I don't understand the limitation that "neither Alice nor Bob is allowed, in any way, to affect the preparation of the initial state." Why shouldn't Alice create the initial state?" If Alice creates the initial state, she can send a message encoded within.
    - therein 11y ago
      I was thinking of that too. Do you think that would add additional latency as the entanglement needs to boot and initialize? It also feels like we would be wasting some bandwidth because the tampering of the pipe will give us 1-bit of information rather than the pipe providing us with four. But hey, it is FTL anyway.

Entanglement can't be used for communication. https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem

photonic29 11y ago
But it can be used for security: http://www.nature.com/news/2008/080827/full/news.2008.1067.html http://www.nature.com/news/2008/080827/full/news.2008.1067.h...
- Florin_Andrei 11y ago
  Right. So connected the usual way, but using QM for security.
igravious 11y ago
I was going to post that link. This is the standard theory, isn't it? Most physicists subscribe to this, regardless of their interpretation of quantum mechanics (Copenhagen, De Broglie–Bohm, and so on?)
- dogma1138 11y ago
  Yes basically if you build say 2 entangled bytes you'll basically get random data out of them every time you measure / set their state you'll basically get random data. The only way to make the data "make sense" is to share the measurements between both observers on a side channel. But and that's the big but which i don't understand and couldn't get a decent explanation from anyone who i know has some / more understanding that i do in QPT. Yes i understand if you got 2 observers Alice and Bob both of them with a pair of say you got a pair of 12 entangled quantum bytes. Bob can't tell by random measurement if Alice has done something since the state of his 12 qbytes is "random", however if the interpreted say say's Hello World! or I Just Changed It why Bob can't superimpose additional information he has such as the knowledge of the English language to interpolate that Alice actually did something. On top of that the no information theorem is also tied to the no-cloning theorem which conflicts with well with how some one would explain quantum teleportation. The explanation I managed to find is that the no-cloning and no-teleportation theorems do not prevent quantum teleportation but rather classical one which means that you cannot encode a quantum state into a classical system and then clone/teleport that information into another quantum system, but you can do it from one quantum system to another which is where my brains starts to scream. http://courses.cs.washington.edu/courses/cse599d/06wi/lecturenotes4.pdf http://courses.cs.washington.edu/courses/cse599d/06wi/lectur...
omnipedal 11y ago
They already teleported information via similar means, so I would hope this doesn't mean FTL communication is impossible.
- ikeboy 11y ago
  It does mean that, actually.
  - omnipedal 11y ago
    https://en.wikipedia.org/wiki/John_G._Cramer https://en.wikipedia.org/wiki/John_G._Cramer This guy seems to believe otherwise and many other scientific breakthroughs were declared as impossible before they were done, it is unwise to cling to limiting beliefs like that as that kind of attitude prevents technological advancement. In fact, it can be speculated that messages could be sent in the future as well as in the past, and other parallel universes as well.
    - ikeboy 11y ago
      All his experiments have failed. See https://faculty.washington.edu/jcramer/NLS/NL_signal.htm https://faculty.washington.edu/jcramer/NLS/NL_signal.htm People have been trying to use QM to show FTL communication since QM was discovered, it doesn't work. >In fact, it can be speculated that messages could be sent in the future as well as in the past, and other parallel universes as well. Yes, you can speculate whatever you want, that doesn't make it any truer.
      - omnipedal 11y ago
        It's only 2015, I think it's a little ridiculous to make far sweeping conclusions about whole realms of science supposedly not working based on limited current understanding of science.
        ikeboy 11y ago
        We've known about QM for 80 years. It's given accurate predictions for all that time. What exactly do you think is limited in currnt understanding of science?
moron4hire 11y ago
I don't understand the limitation that "neither Alice nor Bob is allowed, in any way, to affect the preparation of the initial state." Why shouldn't Alice create the initial state? If we can use the quantum entanglement to determine if some Eve has intercepted a message between Alice and Bob, then why can't we use the fact of tampering as the data pipe? Why shouldn't Alice create the initial state and Bob use the quantum entanglement to communicate back? Use two constant photon streams between the two, one from Alice to Bob, one from Bob to Alice. The photons that are emitted are identical--it's notionally a carrier wave. Alice checks to see if Bob "tampers" with the photons. The actual data encoded in the photon itself isn't important. Say I fire a laser beam to the Moon. It's going to take a second and a half to get there. I send one half of my entangled pair to the Moon and I send the other half down a fiberoptic delay line. In 1.5 seconds, I start checking whether or not my entangled photons have been tampered with, and that is the data stream back from the moon.
- ikeboy 11y ago
  >If we can use the quantum entanglement to determine if some Eve has intercepted a message between Alice and Bob, then why can't we use the fact of tampering as the data pipe? You can't; quantum key distribution requires a classical channel as well. See https://en.wikipedia.org/wiki/Quantum_key_distribution#BB84_protocol:_Charles_H._Bennett_and_Gilles_Brassard_.281984.29 https://en.wikipedia.org/wiki/Quantum_key_distribution#BB84_... >After Bob has measured all the photons, he communicates with Alice over the public classical channel. Edit: also, "I don't understand the limitation that "neither Alice nor Bob is allowed, in any way, to affect the preparation of the initial state." Why shouldn't Alice create the initial state?" If Alice creates the initial state, she can send a message encoded within.
  - therein 11y ago
    I was thinking of that too. Do you think that would add additional latency as the entanglement needs to boot and initialize? It also feels like we would be wasting some bandwidth because the tampering of the pipe will give us 1-bit of information rather than the pipe providing us with four. But hey, it is FTL anyway.