A
quantum bit is a measure of data stored in a quantum information system. Simply put, 1 qubit can store an infinite amount of classical data (numbers, words, etc.) but only 1 bit can ever be extracted. This is because a qubit is a set of two numbers (a
vector in 3d space,) which can go on forever. For example, the numbers could be (
3.1415926535897...,
2.7182818...) The data is mostly useless, because when measured, a qubit gives a value: 1 or 0. There are
algorithms, however, that allow
quantum computing to use this "hidden" data more effectively than classical data, for instance by
factoring large
pseudoprimes.
Hardy, Yorick. Steeb, Willi Hans. "Introduction" Classical and Quantum Computing: With C++ and Java Simulations. Pg. ii-xxv.
Nielsen, Michael A. "Rules for a Complex Quantum World" Scientific American, November 2002.