Solution

ID: past-exam-of-the-short-options-paper-of-the-physics-prelims-of-the-university-of-oxford/2019/s3/3/b/solution

Assume the given wavefunction is zero outside . Wavefunction normalization requires
An arbitrary overall quantum phase is unobservable, so choose the positive real representative .
The linear ramp state in an infinite square well has a boundary subtlety: the limiting value at is , rather than zero. The function is still a normalized element of the well's Hilbert space , so position measurement and energy-projection probabilities are meaningful. It is not in the domain of the Dirichlet Hamiltonian, nor is it a finite-energy box state. Altering the value at the single endpoint does not cure its nonzero boundary trace; a physical finite-energy preparation must smooth the function to zero near the wall. The following probabilities refer to the supplied idealized state.

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