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I've been hearing about qubits for awhile now and don't really understand the significance of having quantum entanglement in a network. Can you entangle multipl

I've been hearing about qubits for awhile now and don't really understand the significance of having quantum entanglement in a network. Can you entangle multiple clients in a mesh, and add or remove entanglements? Is that even possible in the future with this? Or can you manufacture entanglement with each connection, where you initiate the entanglement with a client, and maintain that connection during transport? I'm really just curious if you can use this technology, and literally replace the methods of connections and transport as we use them now, or if this is simply a single function method.

Xcelerate 14y ago
Two cool things: 1) You can have perfectly encrypted communication that no one can eavesdrop on (not even theoretically). 2) You can transmit twice as much classical information using superdense coding: http://en.wikipedia.org/wiki/Superdense_coding http://en.wikipedia.org/wiki/Superdense_coding
- EthanHeilman 14y ago
  >1). You can have perfectly encrypted communication [..] I thought we already had this with quantum encryption (although there a few attacks against it) http://en.wikipedia.org/wiki/Quantum_cryptographyhttp://en.wikipedia.org/wiki/Quantum_cryptography http://en.wikipedia.org/wiki/Quantum_cryptographyhttp://en.w... You can buy real off the shelf devices that will give you quantum encryption. >[..] that no one can eavesdrop on (not even theoretically). Why does this follow? How do we know that there are no measurables that could be used to eavesdrop? >2) You can transmit twice as much classical information using superdense coding: http://en.wikipedia.org/wiki/Superdense_coding http://en.wikipedia.org/wiki/Superdense_coding I think you are right that this is probably the primary advantage, but this article keeps talking about "quantum information" and not entanglement. Can this actually send quBits or just bits?
- droithomme 14y ago
  > You can have perfectly encrypted communication that no one can eavesdrop on (not even theoretically). That is an interesting observation because there is a flip side to it. I can sell you some ordinary looking gear that contains a quantum entanglement based eavesdropper. You can have your device in a cave 20 miles below the earth's surface in a bunker running off diesel generators, with no connections outside the bunker, and here I am, watching everything you do.
  - ZoFreX 14y ago
    Can someone with a greater understanding of quantum physics chime in here - is this correct?
    - btilly 14y ago
      It is not correct. Quantum entanglement is easy to break, and once broken will not re-establish on its own.
  - tgb 14y ago
    How would you do that? Quantum teleportation requires the transmission of 2 classical bits for every qubit, by the only method I know about.
- Daniel_Newby 14y ago
  > You can have perfectly encrypted communication that no one can eavesdrop on (not even theoretically). Not exactly. Quantum "cryptography" assures you that only one party received the data, but not who that other party is. There is no authentication. To prevent a man in the middle attack, you have to use a conventional message authentication code, and the system as a whole is no stronger than the MAC algorithm.
  - Xcelerate 14y ago
    Well, I was implying a few things such as a secure channel already being set up and running.
sp332 14y ago
You can transport quantum states with quantum networks. So you can do a quantum computation in one place, transmit the quantum data somewhere else, do more processing, etc. and then only measure & collapse the waveform when you're done.

Xcelerate 14y ago

Two cool things: 1) You can have perfectly encrypted communication that no one can eavesdrop on (not even theoretically). 2) You can transmit twice as much classical information using superdense coding: http://en.wikipedia.org/wiki/Superdense_coding http://en.wikipedia.org/wiki/Superdense_coding

EthanHeilman 14y ago
>1). You can have perfectly encrypted communication [..] I thought we already had this with quantum encryption (although there a few attacks against it) http://en.wikipedia.org/wiki/Quantum_cryptographyhttp://en.wikipedia.org/wiki/Quantum_cryptography http://en.wikipedia.org/wiki/Quantum_cryptographyhttp://en.w... You can buy real off the shelf devices that will give you quantum encryption. >[..] that no one can eavesdrop on (not even theoretically). Why does this follow? How do we know that there are no measurables that could be used to eavesdrop? >2) You can transmit twice as much classical information using superdense coding: http://en.wikipedia.org/wiki/Superdense_coding http://en.wikipedia.org/wiki/Superdense_coding I think you are right that this is probably the primary advantage, but this article keeps talking about "quantum information" and not entanglement. Can this actually send quBits or just bits?
droithomme 14y ago
> You can have perfectly encrypted communication that no one can eavesdrop on (not even theoretically). That is an interesting observation because there is a flip side to it. I can sell you some ordinary looking gear that contains a quantum entanglement based eavesdropper. You can have your device in a cave 20 miles below the earth's surface in a bunker running off diesel generators, with no connections outside the bunker, and here I am, watching everything you do.
- ZoFreX 14y ago
  Can someone with a greater understanding of quantum physics chime in here - is this correct?
  - btilly 14y ago
    It is not correct. Quantum entanglement is easy to break, and once broken will not re-establish on its own.
- tgb 14y ago
  How would you do that? Quantum teleportation requires the transmission of 2 classical bits for every qubit, by the only method I know about.
Daniel_Newby 14y ago
> You can have perfectly encrypted communication that no one can eavesdrop on (not even theoretically). Not exactly. Quantum "cryptography" assures you that only one party received the data, but not who that other party is. There is no authentication. To prevent a man in the middle attack, you have to use a conventional message authentication code, and the system as a whole is no stronger than the MAC algorithm.
- Xcelerate 14y ago
  Well, I was implying a few things such as a secure channel already being set up and running.

sp332 14y ago

You can transport quantum states with quantum networks. So you can do a quantum computation in one place, transmit the quantum data somewhere else, do more processing, etc. and then only measure & collapse the waveform when you're done.