Have commercial quantum computers finally arrived?

November 19, 2007 - 0:0

A Google scientist seems to hope so but, unfortunately, the answer is probably no. Dr. Hartmut Neven, Google's expert on image searching, was involved in a demonstration of quantum computing on Monday - even though most scientists are extremely doubtful that any real quantum computing took place.

Google is experimenting with image searches that use the image itself, not just keywords (try adding ""&imgtype=face"" to the URL of any image search), but it's hit-and-miss and makes huge demands on conventional computers, because it involves trying a vast number of possible matches and solutions.
In theory quantum computers could help, by applying a basic principle of quantum mechanics - that a system isolated from interaction with the rest of the world exists in every possible state at the same time.
If we could keep a computer in this ""coherent"" quantum state for long enough, it could process every possible input at the same time, as if we had millions of computers in parallel universes. Then all you need do is make the quantum state ""collapse"" in a way that produces an answer you can recognize as the result of your computation.
Researchers are struggling to build big enough quantum computers (with enough quantum bits or ""qubits"") and keep them isolated in a coherent state long enough to do real work. Any photon of interaction will destroy the coherence - and the more qubits you have, the greater the chances of interaction. The academic world has only achieved systems with handfuls of qubits that can stay coherent for a few microseconds.
Monday's demo, at the SC07 supercomputing show in Reno, Nevada, used an algorithm from Dr Neven, whose company Neven Vision was bought by Google last year, running on a system that D-Wave Systems of Canada claims has 28 qubits. D-Wave uses ""adiabatic"" quantum computing, a method that it says can solve specific problems without the need for long decoherence times. It showed an apparent 16-qubit system in February (Computers are about to take a quantum leap into the future, February 8, tinyurl.com/28z4xp).
However, other scientists are dubious because D-Wave won't publish the results or discuss them in depth, and that's anathema in a world that prefers to progress by peer review and independent replication rather than press conferences: ""Rather than answering scientists' questions about what, if anything, they've actually done that's novel, they seem to have descended ever further into the lowest kind of hucksterism,"" says Scott Aaronson, assistant professor of electrical engineering and computer science at MIT.
""The interest of D-Wave for me is mainly one of psychology, business and the margins of science,"" says professor Andrew Steane of the center for quantum computation at the University of Oxford. ""My conclusion is that I suspect they are misleading themselves.""
(Source: Guardian)