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August 21, 2006

More superconducting quantum computer details

The Dwave systems superconducting quantum computer is designed only for Maximum Clique NP-complete problems. This is the same as Maximum Independent Set and Minimum Vertex Cover.

Max Clique is known to be “really really hard”, in the sense that it is intractable to even get good approximate solutions. It is APX complete

From one of the comments by Gordon Rose on his prior posts:
1. (for experts): The machine we’re building is NOT a conventional classical RSFQ processor. My post (aimed primarily at beginners) was just to provide information on some history of superconducting processors as context for later posts.

2. (sort of for experts): The machines we’re building are real quantum computers, yes with real qubits and everything. I’m going to describe quite a bit about the processor architecture in follow on posts so stay tuned.

3. (for experts): Again this is something I’m going to describe at length in a follow on post, but I’d like to flag it here because it was raised in a couple of comments. There is more than one model of quantum computation, and the one most people are familiar with is the “gate model”. Our machines are not gate model machines. They use a different underlying (but equivalent) computational model.
[Tutorial on quantum computing models]
Tutorial on quantum computing principles

4. About the low power comment: It doesn’t take much more power than what you get out of a wall socket to cool a chip to milliKelvin and keep it there. The fridges, even though they look imposing, draw very little power.

5. [refuting marketing claims] [my note: Dwave systems has raised $20+ million.]

6. About our name: Although we’re called D-Wave everything we do is built using niobium (which is not a D-Wave superconductor).

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