Determination of the one-electron reduced Wigner function for a molecular crystal

The Wigner function provides a complete phase-space representation of a quantum state. Yet, direct experimental access to such a quantity for electrons in crystalline solids remains an elusive goal. Here, we report the first reconstruction of an experimental one-electron Wigner function in a molecular crystal. By jointly refining an ensemble N-representable model against high-resolution X-ray diffraction structure factors and directional Compton profiles, we reconstruct a 6D phase-space distribution consistent with both position- and momentum-space data. The reconstructed Wigner function exhibits pronounced negative regions that provide a direct indication of the non-classical nature of the electronic state and shows remarkable agreement with correlated post-Hartree-Fock calculations. Our results demonstrate that complementary scattering experiments can be unified within a single phase-space tomography approach, opening a route towards experimentally reconstructed electron quantum states in crystalline materials.