The study explores the complex interplay of strong Coulomb interactions, quantum effects, and thermal excitations in warm dense matter, focusing on light elements. A breakthrough in path integral Monte Carlo (PIMC) simulations allows for the accurate description of electronic correlations without nodal restrictions. This method is applied to strongly compressed beryllium to analyze X-ray Thomson scattering (XRTS) data from the National Ignition Facility (NIF), achieving excellent agreement between simulation and experiment. The analysis reveals unprecedented consistency in independent observations without empirical input parameters. The research highlights the importance of understanding warm dense matter (WDM) for planetary modeling, inertial confinement fusion, and astrophysical phenomena. The PIMC approach overcomes the computational challenges of the fermion sign problem, providing a powerful tool for studying the quantum behavior of matter under extreme conditions. The results have significant implications for benchmarking existing density functional theory (DFT) approaches, developing advanced nonlocal exchange-correlation functionals, and advancing nuclear fusion and astrophysics research.The study explores the complex interplay of strong Coulomb interactions, quantum effects, and thermal excitations in warm dense matter, focusing on light elements. A breakthrough in path integral Monte Carlo (PIMC) simulations allows for the accurate description of electronic correlations without nodal restrictions. This method is applied to strongly compressed beryllium to analyze X-ray Thomson scattering (XRTS) data from the National Ignition Facility (NIF), achieving excellent agreement between simulation and experiment. The analysis reveals unprecedented consistency in independent observations without empirical input parameters. The research highlights the importance of understanding warm dense matter (WDM) for planetary modeling, inertial confinement fusion, and astrophysical phenomena. The PIMC approach overcomes the computational challenges of the fermion sign problem, providing a powerful tool for studying the quantum behavior of matter under extreme conditions. The results have significant implications for benchmarking existing density functional theory (DFT) approaches, developing advanced nonlocal exchange-correlation functionals, and advancing nuclear fusion and astrophysics research.