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In quantum computing, a qubit () or quantum bit (sometimes qbit) is a unit of quantum information—the quantum analogue of the classical bit. A qubit is a two-state quantum-mechanical system, such as the polarization of a single photon: here the two states are vertical polarization and horizontal polarization. In a classical system, a bit would have to be in one state or the other. However quantum mechanics allows the qubit to be in a superposition of both states at the same time, a property which is fundamental to quantum computing. ==Origin of the concept and name== The concept of the qubit was unknowingly introduced by Stephen Wiesner in 1983, in his proposal for quantum money, which he had tried to publish for over a decade.〔 〕〔A. Zelinger, ''Dance of the Photons: From Einstein to Quantum Teleportation'', Farrar, Straus & Giroux, New York, 2010, pp. 189, 192, ISBN 0374239665〕 The coining of the term "qubit" is attributed to Benjamin Schumacher.〔 〕 In the acknowledgments of his paper, Schumacher states that the term ''qubit'' was invented in jest due to its phonological resemblance with an ancient unit of length called cubit, during a conversation with William Wootters. The paper describes a way of compressing states emitted by a quantum source of information so that they require fewer physical resources to store. This procedure is now known as Schumacher compression. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「qubit」の詳細全文を読む スポンサード リンク
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