A log-derivative formulation of the prefactor for the semiclassical Herman-Kluk propagator

A log-derivative formulation of the prefactor term appearing in the semiclassical Herman-Kluk propagator is presented. The resulting new expression is found in practice to avoid the branch cut problem which has hampered previous formulations. The enhanced performance of the log-derivative version of the prefactor has been confirmed by testing it on several one- and two-dimensional model problems. This log-derivative algorithm is also incorporated in the forward-backward initial value representation and applied to a model of the double-slit diffraction problem.