  The control of thermal decoherence via dynamical decoupling and via the
quantum Zeno effect (Zeno control) is investigated for a model of trapped ion,
where the dynamics of two low lying hyperfine states undergoes decoherence due
to the thermal interaction with an excited state. Dynamical decoupling is a
procedure that consists in periodically driving the excited state, while the
Zeno control consists in frequently measuring it. When the control frequency is
high enough, decoherence is shown to be suppressed. Otherwise, both controls
may accelerate decoherence.
