Before revision:  Exact time-dependent solutions of the CME---which typically consists of infinitely many coupled differential equations---are rare, and are valuable for numerical benchmarking and getting intuition for the behavior of more complicated systems.
After revision:  Exact time-dependent solutions of the CME -- which typically consists of infinitely many coupled differential equations---are rare, and are valuable for numerical benchmarking and getting intuition for the behavior of more complicated systems.