Quantum superposition

Quantum superposition is a fundamental principle of quantum mechanics. It states that, much like waves in classical physics, any two (or more) quantum states can be added together ("superposed") and the result will be another valid quantum state; and conversely, that every quantum state can be represented as a sum of two or more other distinct states. Mathematically, it refers to a property of solutions to the Schrödinger equation; since the Schrödinger equation is linear, any linear combination of solutions will also be a solution.

An example of a physically observable manifestation of superposition is interference peaks from an electron wave in a double-slit experiment.

Another example is a quantum logical qubit state, as used in quantum information processing, which is a linear superposition of the "basis states" ${\displaystyle |0\rangle }$ and ${\displaystyle |1\rangle }$. Here ${\displaystyle |0\rangle }$ is the Dirac notation for the quantum state that will always give the result 0 when converted to classical logic by a measurement. Likewise ${\displaystyle |1\rangle }$ is the state that will always convert to 1.

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