Solution
= Solution
$\Delta_\psi Q=\sqrt{\langle Q^2\rangle-\langle Q\rangle^2}$. The <Robertson uncertainty principle> is
$$
\boxed{\Delta A\,\Delta B\ge\frac12|\langle[A,B]\rangle|.}
$$
= Solution
$\Delta_\psi Q=\sqrt{\langle Q^2\rangle-\langle Q\rangle^2}$. The <Robertson uncertainty principle> is
$$
\boxed{\Delta A\,\Delta B\ge\frac12|\langle[A,B]\rangle|.}
$$