Show that the minimum value of $E(p, x) \equiv p^{2} / 2 m+\frac{1}{2} m \omega^{2} x^{2}$ with respect to the real numbers $p, x$ when they are constrained to satisfy $x p=\frac{1}{2} \hbar$, is $\frac{1}{2} \hbar \omega$. Explain the physical significance of this result.