Re:Cambridge launches UK’s first quantum network
by lallysingh on Tuesday July 10, 2018 @04:04PM
(#17501587)
But you can then twiddle with these photons after exchange right?
Use them to communicate after?
Otherwise what's the point?
Re:Cambridge launches UK’s first quantum network
by roywiggins on Tuesday July 10, 2018 @05:24PM
(#17502317)
The theorem says that you specifically can't communicate with entanglement alone. It's spooky, but just non-spooky enough to forbid building an ansible. If you poke one part of an entangled pair, you can't actually force which state you will get. You will get a measurement, and the other can be measured as well and they will both be observed in some state- but you can't push one leftwards to get the other to go rightwards.
If you could, high speed traders would not bother with microwave links.
Quantum networks are (in theory) impossible to snoop on without detection, so they are useful for distributing cryptographic keys. They might be useful to pass quantum states around between quantum computers if they're reliable enough.
Quantum mechanics allows for superdense coding, where you get a bit more than one bit per particle, but it's probably not really helpful.