# Spectrum

Finds eigenstates and eigenvalues of any operator.

## Input

• $H$: Hamiltonian

## Output

• $\{ \psi_n \}$: list of states - the list of eigenstates of the operator
• $\{ E_n \}$: list of scalars - the list of eigenvalues of the operator

## Content

The input-field sets the index of the highest of eigenstates/-values to be calculated. So if this field reads "0", only the groundstate and corresponding value is found. For "1", the node calculates the ground- and first excited states.