  This article provides an exact formula for the signal n-point correlation
functions of detectors continuously measuring an arbitrary quantum system, in
the presence of detection imperfections. The derivation uses only continuous
stochastic calculus techniques, but the final result is easily understood from
a discrete picture of repeated interactions with qubits or from a parallel with
continuous matrix product states. This result provides a crude yet efficient a
way to estimate system parameters directly from experimental data, without
requiring non-linear state reconstruction.
