A C-EQUATIONS(+ LIBRARY USING QUANTUM TRAJECTORIES TO SOLVE QUANTUM MASTER)

Quantum trajectory methods can be used for a wide range of open quantu m systems to solve the master equation by unravelling the density oper ator evolution into individual stochastic trajectories in Hilbert spac e. This C++ class library offers a choice of integration algorithms fo r three important unravellings of the master equation. Different physi cal systems are modelled by different Hamiltonians and environment ope rators, The program achieves flexibility and user friendliness, withou t sacrificing execution speed, through the way it represents operators and states in Hilbert space. Primary operators, implemented in the fo rm of simple routines acting on single degrees of freedom, can be used to build up arbitrarily complex operators in product Hilbert spaces w ith arbitrary numbers of components, Standard algebraic notation is us ed to build operators and to perform arithmetic operations on operator s and states. States can be represented in a local moving basis, often leading to dramatic savings of computing resources. The state and ope rator classes are very general and can be used independently of the qu antum trajectory algorithms. Only a rudimentary knowledge of C++ is re quired to use this package. The package illustrates how computational physics can profit from object-oriented programming concepts like inhe ritance.