On 5/17/2013 1:21 PM, John Clark wrote:
On Fri, May 17, 2013 at 2:24 PM, meekerdb <meeke...@verizon.net
<mailto:meeke...@verizon.net>> wrote:
> This is what makes one think the D-wave may just be a special purpose machine,
There is no "may be" about it, as I said D-wave's chip is a special purpose machine, but
if it can solve the protein folding problem that's one hell of a special purpose.
But as I understand the problems its solve quickly, they are like Ising and satisfiability
problems - they are essentially minimization over a set of binary choices. I don't think
protein folding can be put in that form because the folds can be at different angles, not
just fold/not-fold.
> For example if you wanted to find the EM field that minimizes the energy
for a
give configuration of charges that's a had problem for a general purpose
computer
using the best digital algorithm, but it's a trivial problem for a special
purpose
computer that just puts charges in those places and measures the field.
Yes then you could forget about calculation and just measure the electric field at any
point you were interested in, but what if you were given the complicated shape of the
electric field and wanted to know the configuration of positive and negative charges
that would produce it? More practically how do you arrange the 20 amino acids, some of
which attract each other while others repel, so that they have the least energy; that is
to say, if I want to form a given shape what linear sequence of amino acids do I need so
that they all fold up into that given shape? Solving this problem would have huge
implications for medicine and for the development of advanced Nanotechnology, but it's a
problem too big for conventional computers but perhaps not for a adiabatic quantum
computer of D-Wave's sort if it had a few thousand qubits or so.
Yes, I'm aware that protein folding is the holy grail of quantum computing - along with
breaking everybody's security codes.
> I'd like to see a paper on its theory of operation.
To my knowledge such a paper does not yet exist, at least not a detailed definitive one.
The paper I gave a link to was about the results of it's operation, it was empirical not
theoretical. They have some general hunches but even the people who made it don't claim
to know exactly how D-Wave's machine works.
That's another thing that makes me suspicious. It's something you hear from inventors of
perpetual motion machines: We can't explain exactly how it works, we just know that it does.
There are even some who say that it doesn't even calculate using quantum mechanical
principles, although the number of people saying that is much smaller now than it was a
year ago. And however it works there is now little doubt that it does.
It works on some problems, but whether it works better than a special purpose computer
designed for that class of problems is still doubtful.
Brent
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