The biggest hurdle in building a transistor that uses quantum effects to move electrons is that the transistor needs to be kept at incredibly low temperatures, a drawback common to anyone who has worked with superconductors.  Since the hoped for benefit of using quantum effect transistors is to avoid the heat generated in current silicon based models, it defeats the entire purpose of the project if you still need a custom cooling solution.  According to this article at The Register you might not need to worry about supercooling your transistors thanks to work being done by Oak Ridge National Laboratory and the MTU group who have created a transistor made up of three nanometer gold quantum dots, insulated by boron nitride nanotubes which successfully transferred electrons at room temperature.  You will not be seeing this technology in consumer products any time soon and the boffins in the EUV lithographic business come up with a few new tricks in the mean time.

"The world might still be 20 years from the end of Moore's Law, but the hunt for technologies to replace semiconductors is going on right now. A group from Michigan Technological University is offering one such alternative: a quantum tunnelling transistor that operates at room temperature."

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