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I had thought that quantum entanglement could not be used for communication because the state that is transmitted is random, and cannot be controlled at either

I had thought that quantum entanglement could not be used for communication because the state that is transmitted is random, and cannot be controlled at either end. But, there are quotes in this article to the contrary. e.g.: “Such a network will enable secure communication without having to worry about eavesdropping, and allow distant quantum computers to connect,” says Tittel. Was my understanding mistaken?

alexmingoia 10y ago
Somewhat related, China has launched the first quantum communications satellite which is meant to prevent eavesdropping using Quantum Key Distribution, http://www.nytimes.com/2016/08/17/world/asia/china-quantum-satellite-mozi.html?_r=0 http://www.nytimes.com/2016/08/17/world/asia/china-quantum-s...
lmm 10y ago
It isn't directly usable for communication, but you can use the shared random state as a one-time pad for provably-secure communication over nonsecure conventional channels.
- d_theorist 10y ago
  Oh! Because both ends have access to the same random bits. Thanks.
semi-extrinsic 10y ago
I took a quantum optics course once. It's true what you say that entanglement can't be used to communicate (by itself), hence no problems with relativity, speed of light etc. This is known as the No-communication theorem: https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem But together with a conventional communications channel (e.g. radio signals), you can use quantum entanglement to create a secure communications channel. This combination is called quantum teleportation (as opposed to just quantum entanglement): https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation
- socmag 10y ago
  Right, "Did you get it?" doesn't need to confirm the information transferred
fu9ar 10y ago
If all you send is more like a checksum or a quantum salt, a few bits of entirely-secure-in-transit entropy in the encryption key could be enough to guarantee secure end-to-end communications in the moment.

alexmingoia 10y ago

Somewhat related, China has launched the first quantum communications satellite which is meant to prevent eavesdropping using Quantum Key Distribution, http://www.nytimes.com/2016/08/17/world/asia/china-quantum-satellite-mozi.html?_r=0 http://www.nytimes.com/2016/08/17/world/asia/china-quantum-s...

lmm 10y ago

It isn't directly usable for communication, but you can use the shared random state as a one-time pad for provably-secure communication over nonsecure conventional channels.

d_theorist 10y ago
Oh! Because both ends have access to the same random bits. Thanks.

semi-extrinsic 10y ago

I took a quantum optics course once. It's true what you say that entanglement can't be used to communicate (by itself), hence no problems with relativity, speed of light etc. This is known as the No-communication theorem: https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem But together with a conventional communications channel (e.g. radio signals), you can use quantum entanglement to create a secure communications channel. This combination is called quantum teleportation (as opposed to just quantum entanglement): https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation

socmag 10y ago
Right, "Did you get it?" doesn't need to confirm the information transferred

fu9ar 10y ago

If all you send is more like a checksum or a quantum salt, a few bits of entirely-secure-in-transit entropy in the encryption key could be enough to guarantee secure end-to-end communications in the moment.