  We use our newly constructed quantum Gibbs ensemble Monte Carlo algorithm to
perform computer experiments for the two phase coexistence of a hydrogen-helium
mixture. Our results are in quantitative agreement with the experimental
results of C. M. Sneed, W. B. Streett, R. E. Sonntag, and G. J. Van Wylen. The
difference between our results and the experimental ones is in all cases less
than 15% relative to the experiment, reducing to less than 5% in the low helium
concentration phase. At the gravitational inversion between the vapor and the
liquid phase, at low temperatures and high pressures, the quantum effects
become relevant. At extremely low temperature and pressure the first component
to show superfluidity is the helium in the vapor phase.

Chemical Physics;Earth and Planetary Astrophysics;Materials Science;Computational Physics