Purdue Builds Quantum-Computing Semiconductor

Bfaber writes: "According to EET, Purdue has created the first examples of quantum computing in a semiconductor. The story can be read here. Read the article for further links that include an audio interview."

Comments

Decoherence

[dido]

decoherence. Quantum dots don't seem to be very promising in this respect, as the minimum time to complete some elementary operation in them is about 10^-6 sec. while the average time to decoherence is about 10^-3 sec. (from Adriano Barenco "Quantum Physics and Computers," Contemp. Phys. 37, 375 (1996). (quant-ph/9612014). Meaning you can probably do about a thousand basic operations before decoherence makes any potential answers worthless. So what if you can pack billions of these quantum dots on a single semiconductor wafer if decoherence prevents you from getting any form of useful results because decoherence destroys any superpositions you have of your entangled quantum states before you can do anything useful. More promising so far have been nuclear magnetic resonance systems (which can take as much as several hours before decoherence sets in, only trouble is making basic operations with NMR systems takes a relatively long time too) or ion traps (if only it weren't so difficult to actually create and isolate large numbers of trapped single ions!).

Maybe the Purdue group will be able to shield their quantum dots from decoherence better than previous research on such objects has done so far. But as far as I know there is no getting around this; the best anyone can do is compute everything and read out your results before decoherence sets in.

This is not such a big breakthrough, folks. Hold onto your hats. If they can show that they can do operations much more quickly than old methods of dealing with quantum dots, or they can keep decoherence at bay longer than anyone expected, that would be the big breakthrough.