量子四位元 - 维基百科，自由的百科全书

量子四位元（Ququads； Quaternary Quantum）是使用|0⟩、|1⟩、|2⟩、|3⟩作為資訊的基本單位，類似古典位元的四進位。^[1]

${\displaystyle |\psi \rangle =\alpha |0\rangle +\beta |1\rangle +\gamma |2\rangle +\delta |3\rangle }$,

${\displaystyle |\alpha |^{2}+|\beta |^{2}+|\gamma |^{2}+|\delta |^{2}=1\,}$

${\displaystyle |0\rangle ={\begin{bmatrix}1\\0\\0\\0\end{bmatrix}},|1\rangle ={\begin{bmatrix}0\\1\\0\\0\end{bmatrix}},|2\rangle ={\begin{bmatrix}0\\0\\1\\0\end{bmatrix}},|3\rangle ={\begin{bmatrix}0\\0\\0\\1\end{bmatrix}}}$

使用兩個量子組合的四進位系統， 相當於古典位元${\displaystyle 4^{2}=16}$，其組合為：${\displaystyle \left\{|00\rangle ,|01\rangle ,|02\rangle ,|03\rangle ,|10\rangle ,|11\rangle ,|12\rangle ,|13\rangle ,|20\rangle ,|21\rangle ,|22\rangle ,|23\rangle ,|30\rangle ,|31\rangle ,|32\rangle ,|33\rangle \right\}}$

1. ^ Abdollah Norouzi Doshanlou, Majid Haghparast, Mehdi Hosseinzadeh, Midia Reshadi. Efficient design of quaternary quantum comparator with only a single ancillary input 2020.01.14. The Institution of Engineering and Technology Journals.