On Physical Realizability of Nonlinear Quantum Stochastic Differential   Equations
  In this article we study physical realizability for a class of nonlinear quantum stochastic differential equations (QSDEs). Physical realizability is a property in which a QSDE corresponds to the dynamics of an open quantum system. We derive a sufficient and necessary condition for a nonlinear QSDE to be physically realizable. 
Muhammad F. Emzir, Matthew J. Woolley, Ian R. Petersen
math.OC math-ph math.MP quant-ph