FLUCTUATIONS AND CORRELATIONS IN QUANTUM-OPTICAL SYSTEMS - AN ALTERNATIVE COMPUTATIONAL APPROACH

We discuss a procedure for the calculation of operator correlation fun ctions that arise frequently in quantum-optics problems. The starting point of our method is the tradiational quantum regression theorem, an d its implementation requires only the solution of the master equation for the density operator of the system of interest. An attractive fea ture of this scheme of calculation is that it offers some distinctive advantages over the conventional Langevin-equations approach or other procedures that rely on the mapping of the density operator into appro priate phase-space distribution functions. Although the practical impl ementation of this method is likely to require numerical computations for virtually every model of physical interest, the procedure is suffi ciently general to allow consideration of both field and atomic correl ation functions, as well as multitime expectation values of mixed prod ucts of atomic and field operators. In this paper we provide a fairly detailed derivation of the formulas of interest, and illustrate our re sults with specific examples and tests of the procedure.