  In this article we describe the incoherent and coherent spin and charge
dynamics of a single electron quantum dot. We use a stochastic master equation
to model the state of the system, as inferred by an observer with access to
only the measurement signal. Measurements obtained during an interval of time
contribute, by a past quantum state analysis, to our knowledge about the system
at any time $t$ within that interval. Such analysis permits precise estimation
of physical parameters, and we propose and test a modification of the classical
Baum-Welch parameter re-estimation method to systems driven by both coherent
and incoherent processes.
