When will useful quantum computers be constructed? Not in the foreseeable future, this physicist argues. Here's why: The case against: Quantum computing.

Quantum Computing IS ALL THE RAGE. It seems like hardly a day goes by without some news outlet describing the extraordinary things this technology promises. Most commentators forget, or just gloss over, the fact that people have been working on quantum computing for decades—and without any practical results to show for it. t IBM notes that quantum computers could "provide breakthroughs in many disciplines, including materials and drug discovery, the optimization of complex systems, and artificial intelligence." Microsoft assures us that quantum computers will "forever alter our economic, industrial, academic, and societal landscape." And journalists repeatedly warn that quantum computers may soon break the encryption that protects the Internet. It has gotten to the point where many researchers in various fields of physics feel obliged to justify whatever work they are doing by claiming that it has some relevance to quantum computing. [ABSTRACT FROM AUTHOR]