  Quantum state estimation, based on the numerical integration of stochastic
master equations (SMEs), provides estimates for the evolution of quantum
systems subject to continuous weak measurements. The approach is similar to
classical state estimation methods in that the quantum trajectories produced by
solving the SME are conditioned on continuous classical measurement signals. In
this paper, we explore the use of classical state estimation for a candidate
quantum system, one based on an experimentally realisable system: a material
object undergoing continuous feedback cooling in an optical trap. In
particular, we demonstrate that classical tracking methods based on particle
filters can be used to track quantum states, and are particularly useful for
higher temperature regimes where quantum state estimation becomes
computationally demanding.
