The Pauli spin matrices in quantum mechanics are
$$
A=\left(\begin{array}{ll}
0 & 1 \\
1 & 0
\end{array}\right) . \quad B=\left(\begin{array}{rr}
0 & -i \\
i & 0
\end{array}\right), \quad C=\left(\begin{array}{rr}
1 & 0 \\
0 & -1
\end{array}\right)
$$ Show that \(A^{2}=B^{2}=C^{2}=1\). (Note carefully that this 1 means the 2 by
2 unit matrix and not the number 1 ; this notation is customary in quantum
mechanics.) Also show that any pair of these matrices anticommute, that is, \(A
B=-B A\), etc. Show that the commutator of \(A\) and \(B\), that is, \(A B-B A\), is
\(2 i C\), and similarly for other pairs in cyclic order.