REVIEWS Quantum computers

advantage by storing, transmitting and processing information encoded in systems that exhibit unique quantum properties? Today it is understood that the answer is yes, and many research groups around the world are working towards the highly ambitious technological goal of building a quantum computer, which would dramatically improve computational power for particular tasks. A number of physical systems, spanning much of modern physics, are being developed for quantum computation. However, it remains unclear which technology, if any, will ultimately prove successful. Here we describe the latest developments for each of the leading approaches and explain the major challenges for the future. I n the past decade, there has been tremendous progress in the experimental development of a quantum computer: a machine that would exploit the full complexity of a many-particle quantum wavefunction to solve a computational problem. The context for the development of quantum computers may be clarified by comparison to a more familiar quantum technology: the laser. Before the invention of the laser we had technological advances in making light: fire, the lantern, the lightbulb. Until the laser, however