

Quantum computer leap - mikecane
http://phys.org/news/2012-05-quantum.html

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da-bacon
Sorry, but no this is not a quantum computer leap. It's a cute paper but
woefully far from a complete solution.

Some problems 1) the procedure appears to require 100 percent detection of
photons (there is no analysis of this in the paper). This is not practical and
ends up being a source of decoherence (the very thing this paper is supposed
to avoid) 2) the scheme depends for its gates and construction of a graph
state (a kind of resource quantum state) on precise settings of polarized beam
splitters, something which will certainly have errors and hence...decoherence
again. 3) the author shows how to create a graph state but makes no mention of
why this state will persist. Why won't it deco here while waiting for the
necessarily adaptive measurement?

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kibwen
_“If a quantum computer existed now, we could solve problems that are
exceptionally difficult on current computers, such as cracking codes
underlying Internet transactions.”_

At least he's being up-front about it, but I'm a little concerned that this
consistently seems to be the most prominent projected use of quantum
computers. What _else_ are they good for, besides allowing exceptionally
wealthy actors to bypass our privacy protections?

~~~
inportb
They are _also_ good for allowing exceptionally wealthy actors to protect
their privacy against other exceptionally wealthy actors who use quantum
computers.

~~~
sp332
Quantum computing is not the same thing as quantum key distribution. QKD is
already in use "in the field". QC is still pretty useless and only exists in
labs.

------
da-bacon
<http://arxiv.org/abs/1111.1319> for the pre print version of this pay walled
publically funded research.

