= One-sided sudden expansion of an infinite square well
{title2=$P_1=32/(9\pi^2)$}
A normalized <ground state> initially supported on $(0,a)$ is $\sqrt{2/a}\sin(\pi x/a)$. Expanding the <infinite square well> to $(0,2a)$ leaves this <wavefunction> unchanged during an ideal sudden switch. Its overlap with the new <ground state> $a^{-1/2}\sin(\pi x/(2a))$ is $4\sqrt2/(3\pi)$, so the <Born rule> gives $32/(9\pi^2)$. This differs from <ground-state overlap after sudden expansion of a square well> with a fixed midpoint, because translation of the new well changes the overlap. Under a fixed final <Hamiltonian operator>, all final <energy eigenstate> <probabilities> remain constant during subsequent <unitary time evolution>.
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