  A complete suppression of the exponential decay in a qubit (interacting with
a squeezed vacuum reservoir) can be achieved by frequent measurements of
adequately chosen observables. The observables and initial states (Zeno
subspace) for which the effect occurs depend on the squeezing parameters of the
bath. We show these_quantum Zeno dynamics_ to be substantially different for
selective and non-selective measurements. In either case, the approach to the
Zeno limit for a finite number of measurements is also studied numerically. The
calculation is extended from one to two qubits, where we see both Zeno and
anti-Zeno effects depending on the initial state. The reason for the striking
differences with the situation in closed systems is discussed.
