Battling Decoherence: The Fault-Tolerant Quantum Computer

Information is something that can be encoded in the state of a physical system, and a computation is a task that can be performed with a physically realizable device. Therefore, since the physical world is fundamentally quantum mechanical, the foundations of information theory and computer science should be sought in quantum physics. In fact, quantum information has weird properties that contrast sharply with the familiar properties of classical information. A quantum computer -- a new type of machine that exploits the quantum properties of information -- could perform certain types of calculations far more efficiently than any foreseeable classical computer. To construct practical quantum computers will be tremendously challenging. A particularly daunting difficulty is that quantum computers are far more susceptible to making errors than conventional digital computers. I will explain the principles of fault-tolerant quantum computation, which can enable a properly designed quantum computer with imperfect components to achieve good reliability.