A Modern Approach to Quantum Mechanics · Problem 6.6

The One-Dimensional Harmonic Oscillator — John S. Townsend

Physics — Quantum Mechanics · expectation-values-momentum

Problem

(a) Show that ⟨px⟩=0\langle p_x\rangle = 0 for a state with a real wave function ⟨x∣ψ⟩\langle x|\psi\rangle. (b) Show that if the wave function ⟨x∣ψ⟩\langle x|\psi\rangle is modified by a position-dependent phase ⟨x∣ψ⟩→eip0x/ℏ⟨x∣ψ⟩\langle x|\psi\rangle \to e^{ip_0 x/\hbar}\langle x|\psi\rangle then ⟨x⟩→⟨x⟩and⟨px⟩→⟨px⟩+p0\langle x\rangle \to \langle x\rangle \quad \text{and} \quad \langle p_x\rangle \to \langle p_x\rangle + p_0

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