An approach towards a simple quantum Langevin equation

We offer a simple way to include energy dissipation in small spatial-dimensional quantum dynamics simulations of a primary quantum system coupled to its surroundings. We show how a quantum Langevin equation can be generated by including a friction operator, (F) over cap, in the primary quantum system's Hamiltonian operator. We demonstrate this approach's computational ease and flexibility through numerical results on both harmonic and anharmonic primary quantum systems. Also, we show how the present approach can be easily generalized to non-Markovian, 'memory' friction. Thus, the approach presented in this work can be used to generate a quantum generalized Langevin equation. (C) 2011 Elsevier B.V. All rights reserved.