Is smarter-than-human AI a realistic prospect?

Although AI that is smarter than humans may sound like science fiction, building superintelligent AI has been one of the goals of AI research for a long time. During the past decade, multiple companies worth billions of dollars have been created with the explicit aim of building such an AI. Many experts believe that smarter-than-human AI is not only possible, but might exist soon; see the related articles for more.