For strongly quantum-degenerate systems at finite temperatures, the fermion sign problem remains the major obstacle to first-principles simulations. In this work, we apply the recently proposed pseudofermion method—designed to overcome the sign problem—to strongly quantum-degenerate uniform electron gases. We find that the pseudofermion method can efficiently and highly accurately infer the energy of the uniform electron gas, while being free from the fermion sign problem. For example, in the strongly quantum-degenerate regime where restricted path-integral Monte Carlo (RPIMC) fails (33 spin-polarized electrons at the density parameter $r_s=0.5$), the relative deviation between the pseudofermion method and the exact configuration PIMC (CPIMC) result is only $0.6\%$. In particular, the pseudofermion method bridges the gap where neither CPIMC nor RPIMC can accurately simulate the regime $1\le r_s\le 2$ at the reduced temperature $\theta =0.0625$. This work demonstrates that the pseudofermion method opens a different pathway for studying strongly quantum-degenerate system in a sign-problem-free manner.

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• Warm-dense matter
• Electron-correlation calculations
• Quantum Monte Carlo