The elementary particle of information used by modern digital computers is the bit—a register or memory element that can be in one of two distinct states, 0 or 1. But we live in a quantum world, and one can design computers in which each elementary unit of information is a quantum bit, or qubit, which can be in any superposition of two quantum states, |0⟩ and |1⟩. A quantum computer built withnsuch components could itself be in a superposition of2ndistinct states, each splinter of the superposition performing its own computation in parallel with all the rest.