The Bloch sphere is a geometric representation of all possible quantum states of a single [[Qubit|qubit]] --- comparable to a globe. Just as every place on earth is represented on a globe, every state of a [[Qubit|qubit]] appears on the Bloch sphere. ![[bloch_sphere.exalidraw.light.svg]] The computational states $\ket{0}$ and $\ket{1}$ are on the North and the South pole of the sphere. In [[Classical Information|classical information theory]] only these to points are used as the classical bits $0$ and $1$. In [[Quantum Technologies|quantum technologies]], the whole surface of the sphere can be used to encode information. The *Bloch sphere* is also a great tool to understand [[Superposition|superposition]]. All states on the sphere are allowed [[Quantum State|quantum states]], however, if we measure the [[Spin|spin]], we only see one of two values $+1/2$ or $-1/2$. The [[superposition]] collapses into one of the two extreme states on the poles during [[Measurement|measurement]]. >[!read]- Further Reading > - [[Qubit]] > - [[Quantum State]] >[!ref]- References > - M. A. Nielsen and I. L. Chuang, _Quantum Computation and Quantum Information: 10th Anniversary Edition_, 10th Anniversary edition (Cambridge University Press, Cambridge ; New York, 2010).