  We investigate the quantum Zeno and anti-Zeno effects in quantum dissipative
systems by employing a hierarchical equations of motion approach which is
beyond the usual Markovian approximation, the rotating wave approximation, and
the perturbative approximation. The quantum Zeno and anti-Zeno dynamics of a
biased qubit-boson model and a biased qutrit-boson model are provided as
illustrative examples. It is found that (i) there exists multiple
Zeno-anti-Zeno crossover phenomena, (ii) the non-Markovian characteristic of
the bath may be favorable for the accessibility of the Zeno dynamics, and (iii)
high bath temperature may add the difficulty in observing the quantum Zeno
effect in quantum dissipative systems.
