A Modern Approach to Quantum Mechanics · Problem 4.3

A System of Two Spin-1/2 Particles — John S. Townsend

Physics — Quantum Mechanics · stationary-states-expectation-values

Problem

Use (4.16) to verify that the expectation value of an observable

A

does not change with time if the system is in an energy eigenstate (a stationary state) and

\hat{A}

does not depend explicitly on time.