  Quantum liquid, in the form of a self-bound droplet, is stabilized by a
subtle balance between the mean-field contribution and quantum fluctuations.
While a liquid-gas transition is expected when such a balance is broken, it
remains elusive whether liquid-gas critical points exist in the quantum regime.
Here we study the quantum criticality in a binary Bose mixture undergoing the
liquid-gas transition. We show that, beyond a narrow stability window of the
self-bound liquid, a liquid-gas coexistence persists, which eventually transits
into a homogeneous mixture. Importantly, we identify two distinct critical
points where the liquid-gas coexistence terminates. These critical points are
characterized by rich critical behaviors in their vicinity, including divergent
susceptibility, unique phonon-mode softening, and enhanced density
correlations. The liquid-gas transition and the critical points can be readily
explored in ultracold atoms confined to a box potential. Our work highlights
the thermodynamic approach as a powerful tool in revealing the quantum
liquid-gas criticality, and paves the way for further studies of critical
phenomena in quantum liquids.
