[ExI] D-Wave's Quantum Computer

[Eugen Leitl]

On Thu, May 23, 2013 at 07:17:58AM +0100, Anders Sandberg wrote:
> 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

There is a curious lack of quantum algorithms, and they all
seem to make use of quantum parallelism (evaluating multiple
branches simultaneously, until entanglement collapses when
you make your measurement to obtain your results).

Even if QC is really all-purpose, it seems to have curious
strengths and weaknesses, and makes VHDL look like a cakewalk.

> gates that implement universal reversible operations. I don't think
> they would be amazingly effective, but they could do it.

My opinion hasn't changed so far: if QC really works (in
the sense of more bang for a given budget of atoms and Joules
vs. classical computation, including nanoelectronics, whic
I don't think is true) it's not really practical.

There might be a mixed domain with spintronics, if you can
combine spin-polarized currents, spin valves and qubits in
solid state close to room temperature. If it works, the
size of qubit registers will be likely small (as you
you said about error correction, and associated power
budget), so no computers the size of a galaxy on top of your palm.