## The More You Know: Qubit

A Qubit, or quantum bit is the fundamental unit of quantum information, it is a mathematical concept satisfying particular properties. The Qubit is the quantum counterpart of the classical bit.

A classical bit can be in one of two different states: 0 or 1, whereas a Qubit can be in the quantum states $|1\rangle$$|0\rangle$ but also in any superposition of these two. That is, the state $|\psi\rangle$  of a Qubit will be of the form

$|\psi\rangle=\alpha|0\rangle + \beta|1\rangle$,

where $\alpha$ and $\beta$ are complex number satisfying

$|\alpha|^2+|\beta|^2=1$.

The states $|1\rangle$ and $|0\rangle$ form the so-called computational basis $\{|1\rangle,|0\rangle\}$. Then, as a mathematical concept, a Qubit is a vector normalized to length 1 in a $2D$ complex vector field.

Just as it’s classical analogue, a Qubit can have many physical realizations: The polarization of a photon, the spin of an electron or a nucleus, the localization of a charge, among other two-state quantum systems.