Compactifying the Electronic Wavefunction II: Quantum Estimators for Spin-Couple

Date: July 26 event was postponed to Aug 9
Title: Compactifying the Electronic Wavefunction II: Quantum Estimators for Spin-Coupled Generalized Valence Bond Wavefunctions

Summary: We present a measurement-driven quantum framework for evaluating overlap and Hamiltonian matrix elements in spin-coupled generalized valence bond (SCGVB) wavefunctions. The approach targets a central difficulty of nonorthogonal valence-bond methods: estimating matrix elements between distinct, generally nonorthogonal configuration state functions. Rather than preparing the full wavefunction on quantum hardware, we reformulate the required quantities as vacuum expectation values of Pauli-string operators that can be accessed using shallow, ancilla-free circuits composed of local Clifford rotations and computational-basis measurements. In contrast to Hadamard-test-based matrix-element estimation, this construction avoids ancilla qubits and controlled operations by reducing the problem to local Pauli measurements. This separates the algebraic construction of the SCGVB problem from the measurement task executed on the quantum register and yields a low-depth strategy compatible with near-term architectures. We demonstrate the framework on square and rectangular H4 using quantum-circuit emulation, where the resulting overlap and Hamiltonian matrices reproduce classical Lowdin-based references with good accuracy across the geometries considered, and where derived Coulson-Chirgwin weights remain chemically consistent. These results support the feasibility of measurement-based quantum assistance for nonorthogonal SCGVB expansions and provide a practical route for incorporating quantum measurements into valence-bond electronic-structure workflows. Reference: https://arxiv.org/abs/2603.12045

Speaker: Dr. Bruna Gabrielly is a postdoctoral fellow at Purdue University. She completed a one-year postdoctoral appointment at the Center for Quantum Information and Control (CQuIC) at the University of New Mexico (UNM) in Prof. Akimasa Miyake's group. She earned her Ph.D. with Summa Cum Laude honors from The Autonomous University of Barcelona (UAB), where she conducted her research in two different institutes affiliated with the Barcelona Institute of Science and Technology (BIST). The rest part of her thesis focused on the exploration of entanglement in graphene-based materials under the supervision of Prof. Stephan Roche and Dr. Aron Cummings at ICN2. The second part delved into the study of many-body quantum states under the guidance of Prof. Antonio Acin at ICFO. Her thesis, titled 'Quantum Information in Lattices,' was funded by a Marie Sklodowska-Curie fellowship. During her Ph.D., she worked in part-time at IBM Quantum and was actively involved in the Qiskit Quantum Community, where she contributed to teaching, mentorship, community building, and cutting-edge research. Before commencing her Ph.D., she received training in the Conformal Bootstrap program. Bruna earned both a Bachelor's and a Master's degree in Theoretical Physics and Chemical Engineering in Recife, Brazil.