Quantum Mechanics: Concepts and Applications · Problem 3.11

One-Dimensional Problems — Nouredine Zettili

Physics — Quantum Mechanics · time-evolution-energy-measurement

Problem

Consider a system whose initial state ∣ψ(0)⟩|\psi(0)\rangle and Hamiltonian are given by ∣ψ(0)⟩=15(304),H=(300005050).|\psi(0)\rangle = \frac{1}{5} \begin{pmatrix} 3 \\ 0 \\ 4 \end{pmatrix}, \quad H = \begin{pmatrix} 3 & 0 & 0 \\ 0 & 0 & 5 \\ 0 & 5 & 0 \end{pmatrix}. (a) If a measurement of the energy is carried out, what values would we obtain and with what probabilities? (b) Find the state of the system at a later time tt; you may need to expand ∣ψ(0)⟩|\psi(0)\rangle in terms of the eigenvectors of HH. (c) Find the total energy of the system at time t=0t = 0 and any later time tt; are these values different? (d) Does {H^}\{\hat{H}\} form a complete set of commuting operators?

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