Qubit

<p>In <a href="/facts/Quantum_computing/nbbcgmvq">quantum computing</a>, a qubit  or quantum bit is a basic unit of <a href="/facts/Quantum_information/Bl9QIvHj">quantum information</a>—the quantum version of the classic binary <a href="/facts/Bit/S972NSaD">bit</a> physically realized with a two-state device. A qubit is a <a href="/facts/Two-state_quantum_system/hQrw3gR9">two-state (or two-level) quantum-mechanical system</a>, one of the simplest quantum systems displaying the peculiarity of quantum mechanics. Examples include the <a href="/facts/Spin_(physics)/4Jvp7e8P">spin</a> of the <a href="/facts/Electron/L0KBo5cW">electron</a> in which the two levels can be taken as spin up and spin down; or the <a href="/facts/Photon_polarization/fh6oqC5E">polarization</a> of a single <a href="/facts/Photon/mFNhAEzA">photon</a> in which the two spin states (left-handed and the right-handed circular polarization) can also be measured as horizontal and vertical linear 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 coherent <a href="/facts/Quantum_superposition/4z1UJg9o">superposition</a> of multiple states simultaneously, a property that is fundamental to <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum mechanics</a> and <a href="/facts/Quantum_computing/nbbcgmvq">quantum computing</a>.
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Qubit open-in-new

Qubit