[ExI] D-Wave's Quantum Computer
Anders Sandberg
anders at aleph.se
Thu May 23 06:17:58 UTC 2013
On 2013-05-22 22:22, Kelly Anderson wrote:
> Even in the most optimistic scenarios, are quantum computers general
> purpose computing machines? Or are they simply machines that are
> capable of solving a certain class of problem extremely rapidly?
As far as I understand, they can be general purpose. You just use gates
that implement universal reversible operations. I don't think they would
be amazingly effective, but they could do it.
Incidentally, since we are talking quantum computation. I have been
trying to track down a proper source on minimum energy dissipation for
it. As far as I get it, by virtue of reversibility QCs can run with no
dissipation - they do not erase bits, so the Landauer limit doesn't
apply. But error correction will be necessary, and error correction
schemes involve dirtying ancilla bits - these bits will have to be
erased, at a thermodynamic cost. Does anybody know a paper placing
bounds on how many ancillas are necessary? I know there are theorems
stating that if the error probability per gate is under a certain
constant in-the-large fault-tolerant computation is possible, but most
of these constructions seem to have huge numbers of gates (literally
millions per bit). Does anybody know a paper that instead minimizes the
number of expected erasures?
Oh, and while still quantum:
http://news.sciencemag.org/sciencenow/2013/05/physicists-create-quantum-link-b.html?ref=hp
Entanglement between particles separated in time. Unsurprising, yet
totally rad.
--
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University
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