  The continuous fuzzy measurement of energy of a single two-level system
driven by a resonant external field is studied. An analysis is given in the
framework of the phenomenological restricted path integral approach (RPI)
(which reduces effectively to a Schrodinger equation with a complex
Hamiltonian) as well as with reference to the microphysical details of a class
of concrete physical realizations. Within the RPI approach it is demonstrated
that for appropriately adjusted fuzziness, information about the evolution of
the state of the system can be read off from the measurement readout E(t). It
is shown furthermore how a measurement of this type may be realized by a series
of weak and short interactions of the two-level system with a quantum
mechanical meter system. After each interaction a macroscopic measuring
apparatus causes the meter to transit into one of two states. The result is
used to generate the energy readout E(t). In this way a complete agreement with
the RPI approach is demonstrated which thus obtains an operational
interpretation.
