Solution

ID: past-exam-of-the-mphil-in-micro-and-nanotechnology-enterprise-course-of-the-university-of-cambridge/2019/paper-2/section-a-ii/15/iv/a/solution

Only have . The printed squared coefficients sum to , rather than exactly one. Normalizing those numbers gives
Treating the coefficients as rounded values of an already normalized state gives the intended approximately answer. Probabilities are sums of squared amplitudes because the energy eigenstates are orthonormal.

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