  There has long been interest to control the transfer of population between
specified quantum states. Recent work has optimized the control law for closed
system population transfer by using a gradient ascent pulse engineer- ing
algorithm [1]. Here, a spin-boson model consisting of two-level atoms which
interact with the dissipative environment, is investigated. With opti- mal
control, the quantum system can invert the populations of the quantum logic
states. The temperature plays an important role in controlling popula- tion
transfer. At low temperatures the control has active performance, while at high
temperatures it has less erect. We also analyze the decoherence be- havior of
open quantum systems with optimal population transfer control, and we find that
these controls can prolong the coherence time. We hope that active optimal
control can help quantum solid-state-based engineering.
