Journal Article

FZJ-2025-05297

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Efficient state preparation for the Schwinger model with a theta term

Bazavov, A. ; Henke, B. ; Hostetler, L. ; Lee, D.Extern* ; Lin, H.-W. ; Pederiva, G. (Corresponding author)FZJ* ; Shindler, A. (Corresponding author)

2025
American Physical Society Ridge, NY

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Please use a persistent id in citations: doi:10.1103/PhysRevD.111.074515  doi:10.34734/FZJ-2025-05297

Abstract: We present a comparison of different quantum state preparation algorithms and their overall efficiency for the Schwinger model with a theta term. While adiabatic state preparation is proved to be effective, in practice it leads to large cnot gate counts to prepare the ground state. The quantum approximate optimization algorithm (QAOA) provides excellent results while keeping the cnot counts small by design, at the cost of an expensive classical minimization process. We introduce a “blocked” modification of the Schwinger Hamiltonian to be used in the QAOA that further decreases the length of the algorithms as the size of the problem is increased. The rodeo algorithm (RA) provides a powerful tool to efficiently prepare any eigenstate of the Hamiltonian, as long as its overlap with the initial guess is large enough. We obtain the best results when combining the blocked QAOA ansatz and the RA, as this provides an excellent initial state with a relatively short algorithm without the need to perform any classical steps for large problem sizes.

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Contributing Institute(s):

1. Jülich Supercomputing Center (JSC)

Research Program(s):

1. 5111 - Domain-Specific Simulation & Data Life Cycle Labs (SDLs) and Research Groups (POF4-511) (POF4-511)
2. DFG project G:(GEPRIS)460248186 - PUNCH4NFDI - Teilchen, Universum, Kerne und Hadronen für die NFDI (460248186) (460248186)

Appears in the scientific report 2025

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