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QI: Fachverband Quanteninformation
QI 4: Quantum Manybody Systems (joint session QI/TT)
QI 4.10: Vortrag
Montag, 9. März 2026, 18:00–18:15, BEY/0245
Symmetry-preserving warm starts for variational ground state preparation — •Ivana Miháliková — Matej Bel University, Národná ulica 12, Banská Bystrica, 97401, Slovakia — Institute of Physics, Slovak Academy of Sciences, Bratislava 84511, Slovakia
Enforcing physical symmetries can dramatically simplify ground-state preparation in the variational quantum eigensolver (VQE). This work considers a 12-spin all-to-all neutrino-inspired model and a 4×3 Heisenberg lattice. In both systems, simple product states are projected onto symmetry subspaces with fixed total spin J and Jz (and, for the Heisenberg lattice, translation and mirror symmetries), then refined using swap-based entangling layers that generate only symmetry-compatible correlations. The resulting warm starts lie well within previously established worst-case upper bounds on the energy error normalized by system size and interaction-graph degree, showing that symmetry-aware initialization can substantially outperform generic guarantees. For the Heisenberg lattice, the symmetry-preserving construction reduces the relevant search space from 4096 basis states to just 9 symmetry-compatible states and increases the effective spectral gap from about 7 to about 28 energy units. Within a VQE setting this yields a smoother optimization landscape and faster convergence with shallow circuits. In practice, the neutrino-inspired model reaches ∼98.8% fidelity within the J=0 subspace, and the Heisenberg lattice exceeds 98.0% fidelity once translation and mirror symmetries are enforced.
Keywords: quantum computing; symmetries