Thursday, March 15, 2007

Update on That "Quantum Computer"

This week's issue of Nature [Nature 446, 245 (15 March 2007)] has a follow up on the recent claim by D-Wave systems of building the first working quantum computer.

D-Wave's approach is known as adiabatic quantum computing. It uses a superconducting microchip to create spinning loops of current, which it says act as qubits, spinning in both directions at once. The qubits then entangle together, putting the entire machine in a 'quantum ground state'. By slowly changing the magnetic fields around the qubits, the computer's operator can then change the computer's entanglement, moving it into a new ground state. Reading this state can, according to the designers, reveal a solution to a complex problem without the need to directly read the state of individual qubits.

My initial reaction to this was how they were hoping to isolate the system and preserves the entanglement. It seems that I'm not the only one who is skeptical on this particular issue.

Aaronson says, however, that external noise could still be a problem for the machine. He also notes that the company has provided no public evidence that it has its system under control — or that its qubits are entangled correctly. According to Lloyd, researchers are still debating whether the entire approach is of any use: "Nobody knows exactly whether adiabatic quantum computing will work or not.

The most amusing part of this article was the response by Geordie Rose, D-Wave's founder and chief technology officer.

But Rose says that the company's scientists are satisfied that the system is indeed operating properly — and that the objective is to try something out and see whether it works, rather than to pin down exactly how it does so. "I understand the scientific community would like to see publications coming from us," he says. "But this project has never been about science, it's about building a machine."

Now, to be fair, he is right at some level. If he can show to some extent that it "works", then he could have said that he created a "computer". However, if he claims that this is a "quantum computer", then this is a different matter. This requires the demonstration that you ARE using the prescribed quantum effects as the mechanism to to produce the result. Considering that this is still a new and unexplored area, making such a claim DOES require scientific verification. Simply saying something like "I have a box, and it spits out results, and so it works" will not cut it, and certainly not if you want to convince that you not only have a box that works, but a box that works using a particular methodology! That is now a different animal than just engineering.


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