  We systematically investigate the ground-state properties of self-bound
droplets of quasi-two-dimensional binary Bose gases by using the Gaussian state
theory. We find that quantum droplets consists two macroscopic squeezed phases
and a macroscopic coherent phase. We map out the phase diagram and determine
all phase boundaries via both numerical and nearly analytical methods. In
particular, we find three easily accessible signatures for the quantum phases
and the stablization mechanism of the self-bound droplets by precisely
measuring their radial size. Our studies indicate that binary droplets
represent an ideal platform for in-depth investigations of the quantum nature
of the droplet state.
