Figure 1: (Top) In conventional time evolution of quantum systems, different input states $|{\psi }^{\text{in}}\rangle$ lead to different output states $|{\psi }^{\text{out}}\rangle$ if a unitary operation $\text{U}$ is applied. (Bottom) Quantum state preparation by reservoir engineering takes a different approach. If the interaction of the system with a bath is engineered such that $|{\psi }_{\text{fin}}\rangle$ is the unique steady state of the dissipative process, then the system is driven into this state irrespective of the initial state initiating the evolution paths ${\rho }_1$, ${\rho }_2$, etc.