Experimental reconstruction of Wigner phase-space current

We experimentally reconstruct Wigner's current of quantum phase-space dynamics. We reveal the ``push-and-pull'' associated with damping and diffusion due to the coupling of a squeezed vacuum state to its environment. In contrast to classical dynamics, where (at zero temperature) dissipation only ``pulls'' the system toward the origin of phase space, we also observe an outward ``push'' because our system has to obey Heisenberg's uncertainty relations. With squeezed vacuum states generated by an optical parametric oscillator at variable pumping levels, we identify the pure squeezing dynamics and its central stagnation point with a topological charge of ``$\ensuremath{-}1$''. This work demonstrates high resolving power and establishes an experimental paradigm for measuring the quantumness and nonclassicality of the dynamics of open quantum systems.