A detailed derivation of a new method for directly computing phase equilibria for quantum fluids is presented. This method is a combination of the path integral formalism with the Gibbs ensemble technique. We use this path integral Gibbs ensemble Monte Carlo method to calculate the vapor-liquid phase diagrams of hydrogen and neon from simulation. Agreement with experimental data is very good. The thermodynamic properties of neon and hydrogen are computed over a wide range of temperatures and pressures. The densities and energies from the simulations are in excellent agreement with literature data, Three different parameter sets for the Lennard-Jones (LJ) neon potential are evaluated by comparing simulation results with experimental data. The Silvera-Goldman potential and Buch LJ potential for hydrogen are evaluated against data on the 100 MPa, 1 GPa, and 2 GPa isobars.