  We present Coupled Electron-Ion Monte Carlo results for the principal
Hugoniot of deuterium together with an accurate study of the initial reference
state of shock wave experiments. We discuss the influence of nuclear quantum
effects, thermal electronic excitations, and the convergence of the energy
potential surface by wave function optimization within Variational Monte Carlo
and Projection Quantum Monte Carlo methods. Compared to a previous study, the
new calculations also include low pressure-temperature (P,T) conditions
resulting in close agreement with experimental data, while our revised results
at higher (P,T) conditions still predict a more compressible Hugoniot than
experimentally observed.
