

Storing Bandwidth with Superdense Coding - Strilanc
http://strilanc.com/quantum/2014/05/03/Storing-Bandwidth-with-Superdense-Coding.html

======
beloch
Bandwidth can be stored in this manner only for as long as qubits can be
stored. At present, most quantum memories realized in experiments have a
storage time of well under a second. Some last slightly longer, but with big
tradeoffs. Stopping decoherence in quantum memories is hard enough that it
will likely be a very long time before classical bandwidth becomes the
bottleneck!

~~~
Strilanc
Relevant, though not yet practical: quantum error correction [1]. There's a
threshold we have to get over, then it gets a lot easier.

 _edit_ and a reddit commenter mentioned this link saying that the current
record for storing a qubit is 39 minutes [2]. Which is about three orders of
magnitude larger than I would have expected, if you discount "just shoot the
photon into space!" solutions.

1:
[http://en.wikipedia.org/wiki/Quantum_error_correction](http://en.wikipedia.org/wiki/Quantum_error_correction)

2: [http://www.livescience.com/41217-long-quantum-bit-
achieved.h...](http://www.livescience.com/41217-long-quantum-bit-
achieved.html)

------
leakybucket
Though I appreciate the idea of 'storing bandwidth' by just sending lots of
qubits ahead of time, that ignores the extra communication overhead needed of
tracking them: When Bob receives a qubit from Alice, he needs to know which of
his qubits it's paired with. That implies that Alice needs to send not just
her qubit, but also some kind of identifier that will allow Bob to match up
the received qubit to its proper Bell pair. That identifier, and any protocol
overhead needed to keep these identifiers in sync between bob and alice, will
consume bandwidth, and reduce the 2x gain.

~~~
oh_sigh
Wouldn't you just be able to pair it in a FIFO order?

