
Quantum hard drive breakthrough - lelf
http://phys.org/news/2015-01-quantum-hard-breakthrough.html
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gradi3nt
This is a misleading headline! This 'hard drive' needs to be in a
superconducting magnet and held at 2K. I'm not aware of any desktop chassis
that comes with a a cryostat...

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hyperbovine
You were expecting to pop down to Best Buy and pick up a couple? All
scientific breakthroughs are like this.

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JD557
Can someone here give a quick explanation on how this would work?

Assuming that everything is stored as qubits and that their internal state is
used as a way to increase storage (and they found a way to make the internal
state not change over time), wouldn't reading from disk destroy this internal
state (not to mention give a random output)?

Have they found a way to measure a qubit in some way without possible loss of
information?

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xnull1guest
Does anyone know if you get a bump from PSPACE closer to EXPSPACE with a
quantum harddrive similar to how BQP gets you closer to EXPTIME from PTIME?

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adrianN
BQP doesn't really get you closer to EXPTIME at all. We don't even know yet
whether it gets you closer to NP. In general, quantum computers only have a
quadratic speed-up as far as we know.

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xnull1guest
PTIME <= BQP <= EXPTIME

This is what I mean by 'closer'.

I had to use EXPTIME rather than NP because of Savitch's Theorem.

> In general, quantum computers only have a quadratic speed-up as far as we
> know.

Not really true? In the time setting, there's the case of sampling problems,
hidden subgroup problems, the evaluation of linear systems, etc. There are
also many other settings (Merlin-Arthur-like round complexity) and
communication complexity where exponential and even superexponential increases
can be had.

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ttol
This is super interesting. Right now we are limited by communication due to
latency from speed of light. With quantum entanglement, does that mean no
latency over great distances? Or is there a latency involved, even in quantum
entanglement?

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zem
no, there's a theorem that states you cannot use quantum entanglement for
communication: [http://en.wikipedia.org/wiki/No-
communication_theorem](http://en.wikipedia.org/wiki/No-communication_theorem)

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Filligree
With one exception, you could use them for a synchronised random number
generator.

It's not as useful as you'd hope, since a cryptographic PRNG theoretically
does the same thing (and you need to individually transport the bits ahead-of-
time), but you can at least be sure the numbers are random and no-one is
spying. Whether or not that counts as communication is up to you.

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ucho
Having quantum entangled particles stored in some crystal sounds better than
requiring direct optical cable connection between peers for some kinds of
quantum computer resistant communication.

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vinceguidry
You still need direct connection and you still need to do key exchange.
Whether you're exchanging keys or quantum particles for the purpose of
generating keys is immaterial for the purposes of security.

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marktangotango
Yay another break through that's supposed to revolutionize computing. I'm
still waiting for my memsistor instantly on memory.

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sp332
Just use flash as RAM then.

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marktangotango
I was ironically highlighting the hype cycle[1] that's common with these types
of 'break through' announcements. Thanks for the down votes though.

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

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sp332
This isn't hype though. No one is pretending that you can buy this tech in "5
years". Every lab that wants this tech is expected to build it themselves
because you can't just buy it anywhere - it's almost anti-hype!

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sitkack
This is great news for a capture everything NSA. Maybe light up every web cam
and every microphone on the planet. What I would do is form a backdoor deal
with HD manufacturers so that I got a generation ahead of regular consumer
tech. The NSA would need to keep HD shipments from manufacturers off their
books.

With its ~20 Billion dollar budget, the NSA could easily hoover (ha) up a
large percentage of the entire hard drive market. It could spend 5% of its
budget to capture %5 of the HD stream.

