The latest buzz surrounded the announcement of a new lab where the Universities Space Research Association, Google, and NASA Ames will operate a quantum computer manufactured by D-Wave, a Canadian computer company. The announcement triggered a wave of breathless stories about the near-magical capabilities of such computers. All this coverage has only made quantum computing seem more impenetrable: what makes a computer “quantum?” Why do we want a quantum computer? And has D-Wave actually built one that lives up to the excitement? To address these questions, we’ll need to start with some background on how computers represent information.