  We investigate the usefulness and viability of the scheme developed by Viola
and Lloyd [Phys. Rev. A 58, 2733 (1998)] to control dephasing in the context of
exciton-based quantum computation with self-assembled quantum dots. We
demonstrate that optical coherence of a confined exciton qubit exposed to
phonon-induced dephasing can be substantially enhanced through the application
of a simple periodic sequence of control pulses. The shape of the quantum dot
has a significant effect on the dephasing properties. Remarkably, we find that
quantum dots with parameters optimized for implementing quantum computation are
among the most susceptible to dephasing, yet periodic decoupling is most
efficient for exactly that type of dot. We also show that the presence of an
electric field, which is a necessary ingredient for many exciton-based quantum
computing schemes, may further increase the control efficiency. Our results
suggest that dynamical decoupling may be a method of choice for robust storage
of exciton qubits during idle stages of quantum algorithms.
