

Storing Bandwidth with Quantum Teleportation - Strilanc
http://strilanc.com/quantum/2014/05/11/Storing-Bandwidth-with-Quantum-Teleportation.html

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marcosdumay
Well, that's a viable commentary on a possible communication channel. Much
more than what I was expecting. But the one thing that it does not do is store
bandwidth, that's a bad title.

It does store "bandwidth" specifically of the quantum channel, and only
because there is no information going through it.

Anyway, the idea of storing qbits is quite interesting, but I don't think even
that would make quantum cryptography useful.

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frozenport
Author should comment on the difficulty of performing a bell-state
measurement.

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Strilanc
(Author here)

Do you have a link? I don't know much about the engineering details, other
than "It's hard. Every part of it is hard.".

Is it the controlled not that's tricky?

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frozenport
A bell-state measurement is the holy grail of QKD. It can only be done 25% of
the time and with great difficulty 50% of the time. So your channel only works
25% of the time!

For entanglement in a single qubit variable, only three distinct classes out
of four Bell states are distinguishable using such linear optical techniques.
This means two Bell states cannot be distinguished from each other, limiting
the efficiency of quantum communication protocols such as teleportation. If a
Bell state is measured from this ambiguous class, the teleportation event
fails.
>>[http://en.wikipedia.org/wiki/Bell_state#Bell_state_measureme...](http://en.wikipedia.org/wiki/Bell_state#Bell_state_measurement)

