Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2023/ib/paper-1/14d/d/solution

For ,
The stationary Schrodinger equation becomes
Hence, choosing the positive root and a positive normalization constant,
The state is even, so . The Gaussian integrals give
and therefore . These values are collected in gaussian eigenstate for a quadratic potential.
Finally, equality in the derivation of the uncertainty relation requires the centred vectors to be linearly dependent with a purely imaginary proportionality constant. Thus for some ,
In position space this says
whose normalizable solutions are
Thus every saturating state is Gaussian up to translation, a plane-wave factor, and an overall phase, as in the equality case of the Heisenberg uncertainty relation.

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