Selecting optimal unrestricted Hartree-Fock trial wavefunctions for phaseless auxiliary-field quantum Monte Carlo: Accuracy and limitations in modeling three iron-sulfur clusters

Phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) relies heavily on the quality of its trial wavefunction to produce accurate predictions, particularly for complex systems with strong correlations. Researchers have investigated the use of unrestricted Hartree-Fock trial wavefunctions to improve the accuracy of ph-AFQMC in modeling three iron-sulfur clusters¹. The choice of trial wavefunction is crucial, as it significantly impacts the method's ability to capture the nuances of correlated electronic systems. Mean-field wavefunctions have emerged as a promising option, offering a balance between computational efficiency and accuracy. However, the optimal selection of these wavefunctions remains a challenge, especially for large systems. The development of effective trial wavefunctions is essential for advancing the capabilities of ph-AFQMC, which in turn has significant implications for the field of quantum computing and its potential to disrupt traditional cryptography. This matters to practitioners because the accuracy of ph-AFQMC predictions directly affects the reliability of quantum computing applications.