# How does time evolution go between degenerate states?

What's the time evolution process between two different degenerate states? Is it also described by Schrodinger equation?

They evolve exactly the same way and their evolution is determined by the Schroedinger equation. A Eigenstate of an Hamiltonian $\left|n\right\rangle$ evolves according to \begin{align} \left|n\right\rangle(t) = \exp(-i E_n t) \left|n\right\rangle \end{align} For two eigenstates with the same eigenvalue $E_n$ the evolution is therefore the same. Another argument is that the superposition of two degnerate eigenstate is also an eigenstate and is therefore stationary, from which we can conclude that their time evolution must be the same.