Robust Stability of Quantum Systems with a Nonlinear Coupling Operator
  This paper considers the problem of robust stability for a class of uncertain quantum systems subject to unknown perturbations in the system coupling operator. A general stability result is given for a class of perturbations to the system coupling operator. Then, the special case of a nominal linear quantum system is considered with non-linear perturbations to the system coupling operator. In this case, a robust stability condition is given in terms of a scaled strict bounded real condition. 
Ian R. Petersen, Valery Ugrinovskii and Matthew R. James
quant-ph cs.SY math.OC