"Scott Aaronson, an expert in the realm of computational complexity theory and the founder of ComplexityZoo.com online encyclopedia of computational complexity theory delivered Carnegie Mellon University's 2011 Buhl Lecture. In his lecture titled "Quantum Computing and the Limits of the Efficiently Computable," Aaronson discusses what quantum computers are, whether they can be built on a large scale, and what's known today about their capabilities and limitations. He goes beyond quantum computers to touch on speculative models of computation, including closed time-like curves and nonlinearities in the Schrodinger equation — an equation that describes how the quantum state of a physical system changes in time." Aaronson's blog post and disscusion in the comments section: http://www.scottaaronson.com/blog... - JoeCamel