  We study the measurement process by treating classical detectors entirely
quantum mechanically. As a generic model we use a point-contact detector
coupled to an electron in a quantum dot and tunneling into the continuum.
Transition to the classical description and the mechanism of decoherence are
investigated. We concentrate on the influence of the measurement on the
electron decay rate to the continuum. We demonstrate that the Zeno (or the
anti-Zeno) effect requires a nonuniform density of states in the continuum. In
this case we show that the anti-Zeno effect relates only to the average decay
rate, whereas for sufficiently small time the Zeno effect always takes place.
We discuss the experimental consequences of our results and the role of the
projection postulate in a measurement process.
