  We present a general method to efficiently design optimal control sequences
for non-Markovian open quantum systems, and illustrate it by optimizing the
shape of a laser pulse to prepare a quantum dot in a specific state. The
optimization of control procedures for quantum systems with strong coupling to
structured environments -- where time-local descriptions fail -- is a
computationally challenging task. We modify the numerically exact time evolving
matrix product operator (TEMPO) method, such that it allows the repeated
computation of the time evolution of the reduced system density matrix for
various sets of control parameters at very low computational cost. This method
is potentially useful for studying numerous optimal control problems, in
particular in solid state quantum devices where the coupling to vibrational
modes is typically strong.
