Representation and Network Synthesis for a Class of Mixed   Quantum-Classical Linear Stochastic Systems
  The purpose of this paper is to present a network realization theory for a class of mixed quantum-classical linear stochastic systems. Two forms, the standard form and the general form, of this class of linear mixed quantum-classical systems are proposed. Necessary and sufficient conditions for their physical realizability are derived. Based on these physical realizability conditions, a network synthesis theory for this class of linear mixed quantum-classical systems is developed, which clearly exhibits the quantum component, the classical component, and their interface. An example is used to illustrate the theory presented in this paper. 
Shi Wang, Hendra I. Nurdin, Guofeng Zhang, Matthew R. James
quant-ph