Quantum computation (QC) holds out tremendous promise for efficiently solving some of the most difficult problems in computational science, such as integer factorization, discrete logarithms, and quantum simulation and modeling that are intractable on any present or future conventional computer. New concepts for QC implementations, algorithms, and advances in the theoretical understanding of the physics requirements for QC appear almost weekly in the scientific literature. This rapidly evolving field is one of the most active research areas of modern science, attracting substantial funding that supports research groups at internationally leading academic institutions, national laboratories, and major industrial-research centers. Well organized programs are underway in the United States, the European Union and its member nations, Australia, and in other major industrial nations. Start-up quantum-information companies are already in operation. A diverse range of experimental approaches from a variety of scientific disciplines are pursuing different routes to meet the fundamental quantum-mechanical challenges involved.