QDYN is a Fortran 95 library and collection of utilities for the simulation of quantum dynamics and optimal control with a focus on both efficiency and precision. Its core features include

• A rich set of data structures for both closed and open quantum systems
• Routines for static system analysis (e.g. diagonalization, emission spectra)
• Propagators for the dynamic equations (Schrödinger equation, master equation)using highly efficient Chebychev and Newton polynomial expansions or theRunge-Kutta method
• Optimal control using Krotov's method, GRAPE/LBFGS, and gradient-free methods

QDYN has an accompanying Python package that may be used for data processing and for integration into a Python-based workflow.