Solution

ID: past-exam-of-the-physics-a-course-of-the-university-of-cambridge/2018/paper-1/section-b/b9/a/solution

The commutator is . To evaluate it for differential operators, apply it to a smooth test wavefunction :
Thus the canonical commutation relation is . The associated Heisenberg uncertainty relation is . Position and momentum cannot both have arbitrarily sharp outcome distributions in the same prepared state, even with ideal measuring apparatus. This concerns quantum-state preparation, not merely a calibration error in a particular instrument.

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