Evaluating Harmonic Oscillator Propagator with Stochastic Decoupling^†

By virtue of stochastic decoupling, the quantum evolution of a harmonic oscillator is converted into two virtual contributions dictated by either a stochastic creation operator or a stochastic annihilation operator. Two approaches are provided to resolve these virtual two evolution operators. One is based on the coherent-state representation and the other deals with the momentum representation after separating out the position and momentum factors. The quantum propagator of the harmonic oscillator is obtained by taking the random average of the combined virtual propagators. The main mathematical exercise of the whole procedure is the calculation of the Gaussian integral.