= Harmonic-oscillator forbidden-region probability
{title2=$P_0=\operatorname{erfc}(1)$}
For the normalized ground state of a reduced <quantum harmonic oscillator>, $\phi_0(q)=\pi^{-1/4}e^{-q^2/2}$ and $E_0=1/2$. Its <classical turning points> are $q=\pm1$. The <Born rule> assigns <probability> $P=2\pi^{-1/2}\int_1^\infty e^{-q^2}\,dq=\operatorname{erfc}(1)\simeq0.157299$ to the <classically forbidden region>. This is a stationary <probability> of detection outside the classical interval. It is not a transmitted flux or an escape rate: the real stationary <wavefunction> has zero <probability current>.
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