Superposition

Superposition is the idea that a valid quantum state can be a linear combination of basis states, not only $\lvert 0 \rangle$ or $\lvert 1 \rangle$ alone.

Key idea

Prepare states like $\lvert \psi \rangle = \alpha \lvert 0 \rangle + \beta \lvert 1 \rangle$ with complex amplitudes satisfying $\lvert \alpha \rvert^2 + \lvert \beta \rvert^2 = 1$. The values $\lvert \alpha \rvert^2$ and $\lvert \beta \rvert^2$ are outcome probabilities for standard measurement in the computational basis.

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