  The goal of this paper is to provide conditions under which a quantum
stochastic differential equation (QSDE) preserves the commutation and
anticommutation relations of the SU(n) algebra, and thus describes the
evolution of an open n-level quantum system. One of the challenges in the
approach lies in the handling of the so-called anomaly coefficients of SU(n).
Then, it is shown that the physical realizability conditions recently developed
by the authors for open n-level quantum systems also imply preservation of
commutation and anticommutation relations.
