Quantum Anamorphosis: A State Preparation Strategy for Simulating Electron Complexity in Many-Unpaired-Electron Systems

Abstract: First introduced in 2020, Quantum Anamorphosis (QA) is a state-preparation strategy that, through tailored molecular orbital transformations, enables a dramatic compression of ground- and excited-state electronic wave functions in spin-adapted many-body bases. This is particularly advantageous for systems with many unpaired electrons which remain a major challenge in modern electronic structure theory.

QA has been successfully applied across a range of problems, from low-dimensional spin models to polynuclear transition metal (PNTM) complexes, key active sites in biological and biomimetic catalysis. For large PNTM clusters such as the P-cluster and FeMo-cofactor a genetic-algorithm-driven QA protocol has also been developed. The resulting wave function compactification is highly beneficial for methods that approximate full-configuration interaction (CI) solutions such as full-CI Quantum Monte Carlo, Generalized Active Space or selected-CI methodologies.

QA has enabled the development of efficient quantum Monte Carlo multi-reference perturbation theory approaches and a Stochastic Difference-Dedicated Configuration Interaction algorithm. In addition, QA has led to a perturbatively corrected, spin-adapted restricted open-shell Hartree-Fock (ROHF) method retaining the computational cost of standard ROHF while allowing access to low-spin states with correct spin symmetry.

In this talk, I will present the key principles of QA, recent methodological developments and applications to magnetic interactions in representative biomimetic clusters (Fe(III)4S4 Mn(IV)3O4 Co(II)3Er(III)O4) and larger architectures such as the P-cluster. Magnetic exchange couplings, spin ladders and temperature-dependent susceptibilities provide stringent benchmarks of the accuracy achievable with QA.

Bio: Giovanni Li Manni is a theoretical and computational chemist and Head of the Strongly Correlated Spin Systems Group in the Electronic Structure Theory Department at the Max Planck Institute for Solid State Research in Stuttgart, Germany. He received his Ph.D. in Chemistry in 2013 from the University of Geneva (Switzerland) under the supervision of Prof. Laura Gagliardi. He held a postdoctoral position at the University of Minnesota and in 2014 joined the Max Planck Institute as a postdoctoral fellow. In 2019, he was appointed group leader at the same institute. He is a core developer and coordinator of the OpenMolcas electronic structure software package.