
IBM shows off quantum computing advances, says practical qubit computers close - ukdm
http://www.extremetech.com/extreme/120229-ibm-shows-off-quantum-computing-breakthroughs-says-qubit-computers-are-close
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DennisP
Probably the most important application: quantum simulation. Solving any but
the simplest quantum mechanics problems takes more computation than we can
muster, but a quantum computer could do it easily. (Iirc, Feynmann wrote about
this idea.)

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palish
Here is Feynman's paper on that subject:
[http://www.cs.princeton.edu/courses/archive/fall04/cos576/pa...](http://www.cs.princeton.edu/courses/archive/fall04/cos576/papers/feynman82/feynman82.pdf)

It's unfortunately the best quality I can find for free. The rest are locked
behind paywalls (which is a tragedy).

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spicyj
This copy looks to be somewhat better:

<http://www.eecs.berkeley.edu/~christos/classics/Feynman.pdf>

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Flow
"According to IBM, 250 qubits would be able to store “more bits of information
than there are atoms in the universe.” This in itself is truly awesome — but
then when you factor in that a quantum computer could perform logic on all of
that data, in parallel, instantaneously"

If this is correct, does this really imply that there are more dimensions than
the 4 we are aware of?

Shouldn't the calculations then be seen in other those extra-dimensions as
well? (Thinking that this could be used to detect extra dimensional life and
perhaps communication with them)

Or does it simply mean that matter has more states than there are particles in
the universe? :-/

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michael_nielsen
Unfortunately, the statement is incorrect. Holevo proved in 1973 that n qubits
can only store n classical bits of information. See:
<http://en.wikipedia.org/wiki/Holevo%27s_theorem>

The statement about performing logic on all that data in parallel is
misleading, at best.

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Flow
Ok, thank you.

I was thinking of <http://en.wikipedia.org/wiki/Hidden_variable_theory> and
that those could be properties of particles skewed into extra dimensions.

This is way over my math and physics skill, but it's still very fascinating.

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zitterbewegung
According to <http://en.wikipedia.org/wiki/Bells_theorem> Hidden variable
theories don't make sense.

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onemoreact
<http://en.wikipedia.org/wiki/Bells_Theorem> works
<http://en.wikipedia.org/wiki/Bells_theorem> does not.

Anyway, that's not quite true, you can get there by giving up principle of
locality or counterfactual definiteness. And in theory nothing requires the
principle of locality to be true.

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michael_nielsen
The actual paper: <http://arxiv.org/abs/1202.5533>

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Intermernet
Yay! Revolutionary tech within our grasp and we're concerned it can decrypt
our VPN traffic! Nice priorities guys.

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jmsduran
I'm pretty sure once quantum computing takes off engineers will be able to
safely port an already existing encryption protocol onto it, it is not a major
concern to me.

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fuzionmonkey
The point being made is that public-key encryption techniques assume that it
is difficult to factor large numbers. Even with modern computers, this takes a
very long time. But this wouldn't be true with quantum computers.

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Zaak
The most popular and well-studied public-key encryption systems use factoring,
but there are lots of other proposed schemes. The ability to quickly factor
products of large primes would cause a temporary upset while alternative
systems are brought in as replacements.

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dmarquis
Its not quite as easy as just swapping out schemes. As I understand it a
practical quantum computer would break all proposed public key encryption
methods except those based on lattice problems. Lattice based cryptography is
still in the preliminary stages of research and is at the moment extremely
slow compared to the currently popular encryption methods.

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bh42222
One of the things quantum computing might be applicable to is protein folding.
If we can compute exactly how a protein would/should fold in linear time...
well that could potentially lead to a cure for EVERYTHING.

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nextparadigms
Is there any way they could be used to replace our PC's in the future, for
general tasks?

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wmf
For most problems, quantum computing is not faster. But when it is
(theoretically) faster, it is _much_ faster. Perhaps we may see quantum
coprocessors one day.

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tobiasSoftware
Obligatory XKCD: <http://xkcd.com/678/>

