A general approach to quantum dynamics using a variational master   equation: Application to phonon-damped Rabi rotations in quantum dots
  We develop a versatile master equation approach to describe the non-equilibrium dynamics of a two-level system in contact with a bosonic environment, which allows for the exploration of a wide range of parameter regimes within a single formalism. As an experimentally relevant example, we apply this technique to the study of excitonic Rabi rotations in a driven quantum dot, and compare its predictions to the numerical Feynman integral approach. We find excellent agreement between the two methods across a generally difficult range of parameters. In particular, the variational master equation technique captures effects usually considered to be non-perturbative, such as multi-phonon processes and bath-induced driving renormalisation, and can give reliable results even in regimes in which previous master equation approaches fail. 
Dara P. S. McCutcheon, Nikesh S. Dattani, Erik M. Gauger, Brendon W.   Lovett, Ahsan Nazir
cond-mat.mes-hall quant-ph