Abstract
We derive a compact expression for the second-order correlation function g⁽²⁾ (0) of a quantum state in terms of its Wigner function, thereby establishing a direct link between g⁽²⁾ (0) and the state's shape in phase space. We conduct an experiment that simultaneously measures g⁽²⁾ (0) through direct photocounting and reconstructs the Wigner function via homodyne tomography. The results confirm our theoretical predictions.