Аннотация:Detection and reconstruction of an external
force acting on a parametric measuring system under
standard quantum limit are considered.
A non-stationary character of vacuum noise is an
essential feature of parametric systems. Due to the parametric
interaction of vacuum noise on the signal and idler
frequencies, the quadrature components of the output
signal are correlated. For optimal detection of an external
force acting on such a system, one can use an optimal
vector signal detection theory utilizing the correlation of
quadrature components. A signal-to-noise ratio for force
detection and the equivalent noise of force reconstruction
are estimated. To realize such measurements one has to
use a phase-sensitive device and dual homodyne detector
with proper local oscillator phase. Connection of the
suggested algorithm with the prescriptions of the theory of
quantum non-demolition measurements is discussed.