  Bistable systems present two degenerate metastable configurations separated
by an energy barrier. Thermal or quantum fluctuations can promote the
transition between the configurations at a rate which depends on the dynamical
properties of the local environment (i.e., a thermal bath). In the case of
classical systems, strong system-bath interaction has been successfully
modelled by the Generalised Langevin Equation (GLE) formalism. Here we show
that the efficient GLE algorithm introduced in Phys. Rev. B 89, 134303 (2014)
can be extended to include some crucial aspects of the quantum fluctuations. In
particular, the expected isotopic effect is observed along with the convergence
of the quantum and classical transition rates in the strong coupling limit.
Saturation of the transition rates at low temperature is also retrieved, in
qualitative, yet not quantitative, agreement with the analytic predictions. The
discrepancies in the tunnelling regime are due to an incorrect sampling close
to the barrier top. The domain of applicability of the quasiclassical GLE is
also discussed.
