Bell 态

阐述

即

\frac{1}{\sqrt{2}}(|00\rangle+|11\rangle), \quad \frac{1}{\sqrt{2}}(|00\rangle-|11\rangle), \quad \frac{1}{\sqrt{2}}(|01\rangle+|10\rangle), \quad \frac{1}{\sqrt{2}}(|01\rangle-|10\rangle)

它们共同构成了一套两量子位空间的基。它们之间可以通过 Pauli 算符互相联系：

\begin{array}{l}\frac{1}{\sqrt{2}}(|00\rangle-|11\rangle)=\left(\sigma_{z} \otimes I\right) \frac{1}{\sqrt{2}}(|00\rangle+|11\rangle) \\ \frac{1}{\sqrt{2}}(|01\rangle+|10\rangle)=\left(\sigma_{x} \otimes I\right) \frac{1}{\sqrt{2}}(|00\rangle+|11\rangle) \\ \frac{1}{\sqrt{2}}(|01\rangle-|10\rangle)=i\left(\sigma_{y} \otimes I\right) \frac{1}{\sqrt{2}}(|00\rangle+|11\rangle)\end{array}