[Cryptography] Quantum Computers for Shor's Algorithm (was Re: Perfection versus Forward Secrecy)

[Perry E. Metzger]

On Sat, 14 Sep 2013 11:49:50 -0700 Tony Arcieri <bascule at gmail.com>
wrote:
> We still haven't seen quantum computers built yet which can truly
> rival their conventional electronic brethren, especially if you
> look at it from a cost perspective. DWave computers are interesting
> from a novelty perspective, but not really ready to replace
> existing computers, even for highly specialized tasks like running
> Shor's algorithm.
> 
> Nevertheless, if you've been following the trends in quantum
> computers over the last few years, they are getting larger, and
> DWave is an example of them moving out of the labs and turning into
> something you can buy.
> 
> I wouldn't be surprised to see a large quantum computer built in
> the next two decades.

DWave has never unambiguously shown their machine actually is a
quantum computer, and even if it is, given its design it very
specifically cannot run Shor's algorithm or anything like it.

I'm unaware of a quantum computer of more than five qbits that has
been demonstrated that can run Shor's algorithm, and that specific
method, using a molecule with five distinct NMR peaks, cannot really
be extended further.

If you can find a reference to quantum computer with more qbits that
can run Shor's algorithm that has been demonstrated in public, I
would be very interested.

(And yes, I'm aware of the two photon device that factored the number
21, though I believe the team used tricks to make that work --
opinions on whether that work could scale would be welcome of course.)

Perry
-- 
Perry E. Metzger		perry at piermont.com